Dissertation submitted for:

Bsc (Hons) Environmental Management

Academic Year: 2012/2013

Nicole Mavrovounioti

Spatial distribution of the ghost crab Ocypode

cursor (L., 1758) along the East coast of Akrotiri

Peninsula in Cyprus during the summer

ii

Abstract

Ghost crabs Ocypode cursor (L., 1758), are a protected species and an important element of the

coastal ecosystems of Akrotiri Peninsula in Cyprus. The spatial distribution of ghost crabs, as

indicated by the number of burrows was studied during the summer of 2012 on the sandy part

of the east coast of the peninsula. Burrow numbers varied during the study period and included

mostly small and medium-sized burrows. The highest number of burrows occurred in July and

the lowest in August, but without a statistically significant difference between the three

months. A definite pattern was observed in the distribution of Ocypode cursor, as the most

populated area was established between 0-10m from the sea with the peak at 6m. Also, a clear,

albeit weak pattern in the distribution of burrow sizes was found, as larger sizes tended to

spread further away from the sea. There was a strong negative correlation between the

number of burrows and anthropogenic disturbance on the beach, as the numbers of burrows in

the southern, undisturbed part were significantly bigger than the ones in the northern,

disturbed one. The sand moisture across the most populated area of Ocypode cursor was

between 11 and 20.5%. Similarly, the sand surface and sediment column temperatures for the

preferred areas of the ghost crab ranged from 22ᵒC to 46ᵒC and 27.2ᵒC to 36ᵒC respectively.

The sediment column was found to be providing the burrows with a thermally stable

environment (28.5-34.4ᵒC) insulating crabs against surface temperature extremes (23.5-

46.1ᵒC). The distribution of Ocypode cursor was found equally in coarse and medium sand

grain.

Abstract: 262 words

Dissertation (excluding abstract): 13,038 words

iii

Table of Contents

Abstract……………………………………………………………………………………………………………………………………..ii

Acknowledgments…………………………………………………………………………………………………………………….ix

1. Introduction……………………………………………………………………………………………………………………….1

2. Literature Review……………………………………………………………………………………………………………...3

2.1. Background and geographical distribution of ghost crabs…………………………………………….3

2.2. Behavioural activity of ghost crabs……………………………………………………………………………….3

2.2.1. Biology of ghost crabs………………………………………………………………………………………………..…4

2.2.2. Diet composition…………………………………………………………………………………………………………..5

2.3. Ghost crab Ocypode cursor (Linnaeus, 1758)………………………………………………………………..8

2.3.1. Physical description………………………………………………………………………………………………………9

2.3.2. Dispersal and activity pattern of ghost crabs during different seasons……………………….12

2.3.3. Effect of human activity on ghost crabs……………………………………………………………………...13

2.3.4. Significance of burrows and their relationship with ghost crabs………………………………..13

2.3.4.1. Orientation, slope, depth and zonation of burrows…………………………………………………..14

2.3.5. Relationship of ghost crabs with environmental variables………………………………………..15

2.3.5.1. Water content………………………………………………………………………………………………….……….15

2.3.5.2. Environmental temperatures…………………………………………………………………………………...16

3. Study Rationale…………………………………………………………………………………………………………....17

3.1. Research aims………………………………………………………………………………………………………….….…17

4. Selection of study area ………………………………………………………………………………………….…….19

4.1. Island of Cyprus……………………………………………………………………………………………………………..19

4.2. Akrotiri Peninsula…………………………………………………………………………………………………………..21

4.2.1. Location……………………………………………………………………………………………………………………..21

4.2.2. Environmental importance………………………………………………………………………………………...22

5. Methods and Materials……………………………………………………………………………………………….24

5.1. Fieldwork methods………………………………………………………………………………………………….…...24

5.1.1. Study area………………………………………………………………………………………………………………...24

iv

5.1.2. Preparation of the study area………………………………………………………………………………………..27

5.1.3. Determination of temporal and spatial distribution, size frequency and burrow density of

ghost crab………………………………………………………………………………………………………………………………..30

5.1.3.1. Data analysis……………………………………………………………………………………………………………….30

5.1.4. Determination of human disturbance…………………………………………………………………………….33

5.1.4.1. Data analysis……………………………………………………………………………………………………………….33

5.1.5. Determination of environmental temperatures…………………………………………………………….34

5.1.5.1. Data analysis……………………………………………………………………………………………………………...34

5.1.6. Determination of moisture content of the sand…………………………………………………………….34

5.1.6.1. Data analysis……………………………………………………………………………………………………………….34

5.1.7. Determination of sand granulometry…………………………………………………………………………….35

5.1.7.1. Sieving and calculation of sand samples……………………………………………………………………..35

5.1.7.2. Data analysis……………………………………………………………………………………………………………...36

5.1.8. Limitations…………………………………………………………………………………………………………………….38

6. Results and Analysis…………………………………………………………………………………………………….…39

6.1. Temporal and spatial distribution, size frequency and burrow density of ghost crab……….39

6.2. Human disturbance……………………………………………………………………………………………………….….51

6.3. Environmental temperatures…………………………………………………………………………………………...54

6.4. Moisture content of the sand……………………………………………………………………………………………59

6.5. Sand granulometry……………………………………………………………………………………………………………61

7. Discussion…………………………………………………………………………………………………………………………63

7.1. Temporal and spatial distribution, size frequency and burrow density of ghost crab……….63

7.2. Human disturbance in relation to burrow density…………………………………………………………….65

7.3. Environmental temperatures in relation to burrow density and diameter……………………….66

7.4. Moisture content of the sand in relation to burrow density and diameter……………………….66

7.5. Sand granulometry in relation to burrow density and diameter……………………………………….67

7.6. Evaluation of hypotheses in relation to research questions……………………………………………..68

8. Limitation and Recommendations for Future work……………………………………………………..69

9. Conclusions……………………………………………………………………………………………………………….…….70

v

References……………………………………………………………………………………………………………………………...71

Appendices 1-13……………………………………………………………………………………………………………………..77

List of Figures

1. Ocypode cursor captured on Lady’s mile beach eating a piece of ham whilst handling a

seaball of Posidonia oceanica..................................................................................................6

2. Ocypode cursor captured on Lady’s mile beach snatching a piece of bread which was then

taken down to its burrow………………………………………………………………………………………………..….6

3. Ocypode cursor (A) and Ocypode burrows (B) were detected in/close to turtle nests on

Lady’s mile beach……………………………………………………………………………………………………………….7

4. The zone of Ocypode cursor (L.)……………………………………………………………………………………..…..8

5. A ghost crab Ocypode cursor (L.) captured on Lady’s mile beach………………………………………10

6. The ghost crab Ocypode cursor has this name as it fits with the sand……………………………....10

7. The vision of Ocypode cursor is capable of 360ᵒ…………………………………………………………..…..11

8. Ocypode cursor captured running on its three pairs of legs…………………………………………..….11

9. Ocypode cursor burrows of male (A) and female and juveniles (B)……………………………………14

10. Location of Cyprus in the Eastern Mediterranean Sea……………………………………………………...19

11. Distribution of Ocypode cursor (L.) in Lara beach (A), Lady’s mile beach (B) and Alagadi

beach (C) in Cyprus…………………………………………………………………………………………………………..20

12. Location of Akrotiri Peninsula in Cyprus…………………………………………………………………………...21

13. Salt Lake of Akrotiri Peninsula…………………………………………………………………………………………..22

14. Major areas of off-road racing …………………………………………………………………………………………23

15. Study area of the East coast of Akrotiri Peninsula………………………………………………………….…25

16. Turtle nesting sites at Akrotiri Peninsula…………………………………………………………………………..26

17. Parking areas at Lady’s mile beach……………………………………………………………………………….…..26

18. Location of plots along the study area of Akrotiri Peninsula………………………………………….….28

19. Pictures of plots…………………………………………………………………………………………………………….….29

20. The temporal distribution of Ocypode cursor along the East coast of Akrotiri Peninsula

during the study period ………………………………………………………………………………………………..….40

vi

21. Weekly recordings of Ocypode cursor burrows along the study area during the study

period……………………………………………………………………………………………………………………………….41

22. Burrow numbers of Ocypode cursor along the study area of Akrotiri Peninsula during the

study period……………………………………………………………………………………………………………………..41

23. Ranking order of plots according to the highest number of Ocypode cursor burrows during

the study period……………………………………………………………………………………………………………….42

24. Percentage of the average number of burrows of the southern and the northern site of the

study area during the study period ………………………………………………………………………………….42

25. Percentage of the average number of burrows of the southern and northern site of the

study area during June (A), July (B) and August (C)……………………………………………………………43

26. Percentage of Ocypode cursor burrows belonging to each of the six size classes recorded

along the study area during the study period……………………………………………………………………43

27. Size frequency distribution for the diameter of the burrow openings of Ocypode cursor

recorded along the study area during the study period…………………………………………………….44

28. Size frequency distribution of the diameter of the burrow openings of Ocypode cursor

along the study area during June (A), July (B) and August (C)……………………………………………44

29. Burrow numbers of Ocypode cursor across the zones of the study area during the study

period……………………………………………………………………………………………………………………………….46

30. Percentage of the average number of burrows of Ocypode cursor across the zones of the

study area during the study period…………………………………………………………………………………..46

31. Burrow numbers of Ocypode cursor along the study area across the zones of the beach

during June (A), July (B) and August (C)………………………………………………………………………….…47

32. Burrow density and diameter of Ocypode cursor with distance from the sea of the study

area during June (A), July (B) and August (C)…………………………………………………………………….48

33. Burrow density and diameter of Ocypode cursor recorded across the zones of the study

area during June (A), July (B) and August (C)…………………………………………………………………….49

34. Percentage of the average number of Ocypode cursor burrows size classes recorded across

the zones of the beach during the study period………………………………………………………………..50

35. Average scale of human disturbance during the study period……………………………………….….52

vii

36. Percentage of the average scale of human disturbance between the two sites of the study

area during the study period………………………………………………………………………………….…………52

37. Scale of human disturbance along the study area of Akrotiri Peninsula during different

periods of the summer………………………………………………………………………………………………..……53

38. Ranking order of plots according to the highest human disturbance during the study

period……………………………………………………………………………………………………………………………….53

39. Average air temperatures during the study period……………………………………………………………56

40. Average temperatures for sand surface of beach zones between times of the day during

June (A), July (B) and August (C)……………………………………………………………………………………….56

41. Average temperature for sediment column of beach zones between times of the day

during June (A), July (B) and August (C)…………………………………………………………………………….57

42. Average temperatures of sand surface (A) and sediment column (B) across the beach zones

during the study period…………………………………………………………………………………………………….58

43. Average counts of moisture content of the sand across the zones of the beach during the

study period……………………………………………………………………………………………………………………..59

44. Sand moisture content taken from the zones of the beach of each plot during June (A), July

(B) and August (C)…………………………………………………………………………………………………………….60

45. Distribution of each of the six size classes recorded in coarse and medium sand grain along

the southern plots of the study area………………………………………………………………………………..62

List of Tables

1. Research structure and summary of the purpose of each chapter………………………………….…2

2. Key characteristics of Ocypode species……………………………………………………………………………..4

3. Grid values and Dimension zones of plots…………………………………………………………………..…..27

4. Particle diameter size and logarithmic phi values of each sieve………………………………….……36

5. Environmental temperatures taken at 6hour intervals through a 24hour period during

June (A), July (B) and August (C) from zones of plot 9……………………………………………………..55

viii

6. Granulometry data relating to the sand samples collected from the zones of each plot of

Akrotiri Peninsula. Md = median grain ( )……………………………………………………………………….62

List of Boxes

1. Key limitations of the research methods employed in this survey……………………………….…38

2. Key limitations of this study and suggestions for future work in this area……………………..69

Photographs were taken by author unless otherwise stated.

ix

Acknowledgements

I would like to give my gratitude to all who helped me throughout the process of this project.

The deepest gratitude is given to my supervisor Dr. Mike Jeffries for his guidance, help and

enthusiasm during this project.

I am also very grateful to Mr. Pantelis Charilaou of the Sovereign Base Areas Environment

Department (SBAED) for providing his vital support and wealth of knowledge.

Particular recognition must be given to Mrs. Samantha Wylie of the SBAED who escorted me

within the military fenced area during my fieldwork in early Monday mornings of the hot days

of the summer.

I would like to thank my family for their constant support and encouragement, especially my

mother Artemis and Harry who helped me with the collection and processing of sand samples,

and the taking of amazing photographs and for making me smile when things got tough. I truly

appreciate their support and encouragement during this project.

Special thanks go to my friend Tony for his special company and encouragement during this

project.

I am very thankful to the Akrotiri Environmental Education and Information Center and its

manager Mr. Thomas Hajikyriakou who provided several specialized instruments used for this

project.

I want to thank the British Military Base of Akrotiri for their kindness and permission to access

the site and carry out my research.

1

1. Introduction

The Decapoda are a very diverse and successful crustacean order, counting more than 8,500

identified species (McMahon and Burggren, 1988) and include the cabs, lobsters, crayfish and

shrimps (Serpent, 2013). Many of the crab species are found in marine and freshwater habitats

whilst some spend their life on land (McMahon and Burggren, 1988). Sandy beach ecosystems

are one of the most threatened environments (Branco et.al., 2010) and major coastal resources

worldwide, supporting large population of vertebrates and invertebrates (Lucrezi et.al., 2009)

and harbouring a marine fauna of enormous ecological diversity (Dahl, 1953). The

overexploitation of coastal areas cause major problems to marine and coastal organisms

(Alfonso et.al., 2007).

The ecology of sandy beaches has been studied during the last two decades. The uppermost

areas of exposed sandy beaches are generally inhabited by a number of amphipods, isopods,

insects and ghost crabs. Due to their abundance, relatively large size and activity, ghost crabs

are the most evident invertebrates of sandy shores (Barros, 2001), and they can be used as an

indicator of human impacts on sandy ecosystems and the health of the environment (Aheto et.

al., 2011; Valero-Pacheco, et.al., 2007). Moreover, they are a key part of the food chain,

playing an important role in the energy transfer from organic detritus and smaller individuals to

larger predators (Fisher and Tevesz, 1979). Last but not least, the burrows of ghost crabs can

modify the complexity of sandy beaches, affecting their productivity and physical environment

(Chan et.al., 2006). Therefore, studying ghost crabs on sandy shores alongside with their

relationship with several issues including human disturbance and ecological variables is very

important and critical research.

This project will be achieved using the structure outlined in Table 1 below.

2

Table 1: Research structure and summary of the purpose of each chapter

Chapter Purpose of Chapter

2 Introducing this research in a context of academic literature is critical in evaluating its

purpose; therefore a deep study of Ocypode cursor and its geographical range, biology,

ecology and behaviour alongside with its relation with human activities and ecological

variables is described.

3 Identification of aims of the study from information obtained in Chapter 2, alongside with

research questions as well as hypotheses created for examining within this project to

determine the spatial distribution of Ocypode cursor along the East coast of Akrotiri

Peninsula and its relationship with human activities and ecological variables.

4 Outline and description of the location and selection of the study area alongside with its

environmental importance.

5 Specification of the study area described in Chapter 4 alongside with the description and

justification of research methods and outlining of the data analysis used for this project

followed by the identification of the key limitations of the methodology obtained.

6 Presentation of results and description of their findings.

7 Interpretation and discussion of the main findings described in Chapter 6 in relation to

existing literature, linking back to the study aims and evaluation whether the data is in

agreement with those hypotheses created in Chapter 3.

8 Key limitations of this project and recommendations for future work in this area.

9 Concluding observations summarising all the previous chapters.

3

2. Literature Review

2.1. Background and geographical distribution of ghost crabs

Ghost crabs are the crabs of the genus Ocypode and are the most widespread of the

Ocypodidae family (Barros, 2001), being commonly found in tropical to subtropical sandy

shores (Türeli, et.al., 2009), occurring in the upper intertidal or the supratidal zones whilst

many Ocypode species venture some distance inland (Turra et.al., 2005), even up to hundreds

of meters back into dunes behind beaches (Hobbs et.al., 2008).

The abundance and presence of ghost crabs on sandy shores is largely controlled by several

prominent physical and ecological variables including beach width and slope, tidal rhythm

(Chan et. al., 2006; Valero-Pacheco, et.al., 2007), salinity range (Griffin 1971; Ewa-Oboho,

1993), high energy weather events, the degree of urbanization (Rosa and Borzone, 2008; Hobbs

et.al., 2008), body size, sediment grain size, intertidal morphodynamics in relation to swash

climate (Quijon et.al., 2001; Dugan et.al., 2000; Sassa and Watabe, 2008), food availability

(Martin, 2006), and the presence of suitable habitat for burrowing, vegetation or shade

(McMahon and Burggren, 1988). However the most important factors that affect their

distribution and activity are those of temperature associated with physiological function and

water (McMahon and Burggren, 1988; Hughes, 1966; Eshky et.al., 1995).

There are over 20 described species of Ocypode around the world. Of these, two occur in the

East Pacific (Ocypode occidentalis and Ocypode gaudichaudii), one in the West Atlantic

(Ocypode quadrata [Fabricius]), two in the East Atlantic (Ocypode cursor [L.] and Ocypode

africana) and the rest of them occur in the Indo-West Pacific (McMahon and Burggren, 1988).

2.2. Behavioural activity of ghost crabs

Ocypode crabs can be seen active during all hours of the day (Shuchman and Warburg, 1978),

but they appear to be more active during night hours when they emerge from their burrows to

maintain them or to forage (Strachan et.al., 1999; Valero-Pacheco, et.al., 2007; Haley, 1969).

Previous studies on Ocypode cursor (L.) showed that in September they were significantly more

active during the night than the day. In July the crab activity during the day was low but in

September the amount of diurnal activity increased (Strachan et. al., 1999). Similarly, studies on

Ocypode cursor at Yumurtalik beach in north-eastern Mediterranean Turkey showed that the

crab activity was higher during the night than the day while during August the crab activity was

very little during the day (Türeli, et.al., 2009). Further studies indicate that adults are nocturnal

while juveniles are diurnal (Hughes, 1966; Chan et. al., 2006) to avoid nocturnal foraging adults

(McMahon and Burggren, 1988; Fisher and Tevesz, 1979). In general the extent of diurnal

4

activity of ghost crabs depends on human activity and the presence of predators on the beach

(Hughes, 1966; Jones, 1972).

2.2.1. Biology of ghost crabs

Studying the biology of ghost crabs is very interesting as discussed in Table 2 below. Ocypode

species can communicate with each other via more than just visual signals (Vannini, 1980b), as

they can produce sounds (Horch, 1975; Salmon, 1983). Calling signals is a unique phenomenon

among the crustaceans, occurring only in the subfamily of Ocypodidae and in some other

terrestrial crabs (Salmon, 1983).

Table 2: Key characteristics of Ocypode species

Characteristics Description Sources Longevity The lifespan of Ocypode species is 2-3 years;

however most crabs found on sandy beaches are 1 year old or even less.

McMahon and Burggren, 1988

Growth ‘Molting’. As the crab grows, it produces a new small soft skeleton underneath their hard one. Then the old skeleton cracks open along the back end of the body and they squeeze themselves out of it. Once the new larger skeleton has hardened, the crab can once again begin actively foraging.

Molting take place during winter inactivity.

McMahon and Burggren, 1988

Gifford, 1962

Reproduction Every 53 days throughout the year when the integument of female is hard

When ghost crabs are about 1 year old.

Occurs near or in the male’s burrow during warm months.

Females make the final decision about whether to mate with males or not. If she leaves his burrow, she is competed for by the other male crabs waiting around.

Females can reach sexual maturity when their carapace length is >25mm while the carapace length of males is >24mm.

Females carry their eggs beneath their bodies

McMahon and Burggren, 1988

Hobbs, et.al., 2008

Izzo and Kothari, 2011; McMahon and Burggren, 1988

McMahon and Burggren, 1988

Izzo and Kothari, 2011

McMahon and Burggren, 1988;

5

and release them in the water after sunset. Although Ocypode crabs cannot swim, females must frequently enter the water to ventilate the eggs by turning them upside down.

Mitchell, 2007; Izzo and Kothari, 2011

Courtship and acoustic displays

Stereotyped movement (waving) of the large major cheliped of males is used by males to attract females.

The ghost crab possesses a special mechanism on its right claw called ‘a stridulating organ’. When the crab strokes the stridulating organ against a point at the bottom of its leg it produces a creaky sound. It occurs for a few days twice a month and may serve as a warning to other crabs not to enter a burrow or may be also used by males to attract females during the breeding season.

Ghost crabs respond to sound transmitted through the substrate and air up to 10m away. Damp sand is a better sound conductor than dry sand, thus moisture content is a primary ecological variable.

McMahon and Burggren, 1988

Salmon, 1983

McMahon and Burggren, 1988; Horch, 1975

2.2.2. Diet composition

Ghost crabs are swift and highly active predators, scavengers and sometimes deposit feeders

(McMahon and Burggren, 1988; Hughes, 1966; Wolcott, 1978). The main activity of ghost crabs

when not associated with their burrows is food searching (Hughes, 1966). They eat particulate

sand and organic matter found among the sand grains, dead fish (Türeli, et.al., 2009), plant

materials and animals in all states of decomposition, flies (Strachan et.al., 1999), insects, ants

and marine organisms (McMahon and Burggren, 1988). Ocypode cursor is primarily a predator

(Ewa-Oboho, 1993) and its diet slightly differs from other ghost crabs as it mainly consists of

terrestrial insects (Myrmicinae) while crustaceans and drifting macroalgae supplement its diet

(Chartosia et.al., 2010). Ocypode cursor was also observed feeding upon various carcasses and

the littoral coastal infauna during the night (Strachan et.al., 1999). Ocypode crabs are also

attracted by discarded food on the beach (Figures 1, 2), eaten mostly during the night as in the

case of Ocypode cursor on Alagadi beach in northern Cyprus (Strachan et.al., 1999). Ocypode

cursor was observed to predate eggs within turtle nests (Strachan et.al., 1999). Ghost crabs

have been stated as one of the most important predator on hatchlings (Hobbs et.al., 2008).

Crab tracks can be seen around newly hatched nests (Strachan et.al., 1999) (Figure 3).

6

When prey is smaller than the crab it is eaten instantly, but when it is heavy, repeated rests

while parts are eaten are required. In case of disturbance the prey is taken down to the burrow;

if not, it is eaten outside the burrow (Hughes, 1966).

Figure 1: Ocypode cursor captured on Lady’s mile beach eating a piece of ham whilst handling a

seaball of Posidonia oceanica

Figure 2: Ocypode cursor captured on Lady’s mile beach snatching a piece of bread which was

then taken down to its burrow

7

Figure 3: Ocypode cursor (A) and Ocypode burrows (B) were detected in/close to turtle nests on

Lady’s mile beach

(A)

(B)

8

2.3. Ghost crab Ocypode cursor (Linnaeus, 1758)

The ghost crabs are semi terrestrial crabs inhabiting the upper intertidal (Turra et.al., 2005)

and supralittoral zones of sandy beaches (Chartosia et.al., 2010) (Figure 4), where they occupy

noticeable golfball–sized burrows (Strachan et.al., 1999). They can also be observed within

high-tide limits in areas extending away from the beach into terrestrial habitats (Türeli et.al.,

2009).

The geographical distribution of ghost crab Ocypode cursor (L.) extends from the Atlantic coast

of West Africa into the Mediterranean where its distribution is increasing (Strachan et.al., 1999;

Chartosia et.al., 2010).

Ocypode cursor is an endangered species, under the protection of Annex II to the Barcelona

Convention (1995) and Annex II to the Bern Convention (1996-1998) (Alfonso et.al., 2007).

Management measures have to be taken to protect these species which is a significant part of

the biodiversity and coastal ecosystems in Cyprus.

Figure 4: The zone of Ocypode cursor (L.)

(Modified version of Education, 2013; Barras, 1963)

9

2.3.1. Physical description

Ocypode are well-known as ghost crabs because of their pale colour fitting with the sand and

providing camouflage (McMahon and Burggren, 1988). When no burrow can be found to run

into, the ghost crab runs to escape from predators making stops to take advantage of its

camouflage colour (Figure 6). Also it can hide and use its stalked eyes as a periscope (Milne and

Milne, 1946). Their large club-shaped stalked eyes and their long, slender legs are both very

useful terrestrial adaptations (McMahon and Burggren, 1988). Although they are able to see

360ᵒ (Figure 7), they cannot see straight overhead. However their vision is so acute that allows

them to grab insects in the air (Mitchell, 2007). They have ten jointed legs two of which are

tipped with claws. One claw is always larger than the other for feeding and digging their

burrows. The other four pairs are pointed legs for walking and running (McMahon and

Burggren, 1988).

Ghost crabs are the fastest runners of all crustaceans reaching 3.4m/sec (McMahon and

Burggren, 1988), moving more than 300m during the day when feeding (Martin, 2006) and not

returning to the same burrows next day (Hobbs et.al., 2008; Wolcott 1978). When they are

walking on their own speed they prefer to walk sideways using all eight legs, as their legs

cannot overlap or interfere with each other (Milne and Milne, 1946). However they can walk

forward and backward (McMahon and Burggren, 1988). At high speeds the crab raises its

hindmost pair of legs clear of the ground and runs with six legs (Milne and Milne, 1946) (Figure

8).

Males are often bigger than females (Branco et.al., 2010). Also the abdomen of both male and

female juveniles is narrow, while the abdomen of adult females is broader than that of the

adult male (Haley, 1969). Ocypode cursor are medium-sized crabs and most species can reach

40-50mm in carapace width (McMahon and Burggren, 1988), constructing burrows 0.6-1.2m

long in the area extending from the water line landward up to 400m (Hobbs et.al., 2008).

Through the maintenance of the galleries the ghost crabs aerate, move and recycle an

important amount of nutrients in the sandy beaches (Türeli, et.al., 2009; Valero-Pacheco, et.al.,

2007).

10

Figure 5: A ghost crab Ocypode cursor (L.) captured on Lady’s mile beach

Figure 6: The ghost crab Ocypode cursor has this name as it fits with the sand

11

Figure 7: The vision of Ocypode cursor is capable of 360ᵒ

Figure 8: Ocypode cursor captured running on its three pairs of legs

12

2.3.2. Dispersal and activity pattern of ghost crabs during different seasons

The ecology of Ocypode species is difficult to study outside their burrows, but when they leave

the sand, the burrows through which they emerge are obviously seen and can be therefore

easily counted and used as a basis of ecological studies (Barras, 1963).

Previous studies on the population of Ocypode cursor at Atlit in northern Israel by Shuchman

and Warburg (1978) showed that there were annual fluctuations in the densities and dispersal

patterns of the crab. They found that the highest number of burrows was counted during

autumn, dropping towards the end of autumn and the beginning of winter. The number of

crabs then increased again in small numbers during the spring in an area between 15-25m from

the sea while during the summer more crabs appeared and were abundant in an area between

5-10m from the sea. A further study carried out by Gilad-Shuchman and Warburg, (1977)

indicated that the dispersal patterns of Ocypode cursor burrows changed over the year with

highest numbers counted during the autumn and summer in an area of 15-20m from the sea,

no crab activity during the winter and appearance again but in small numbers towards the

spring. In contrast, the study on Ocypode cursor at Yumurtalik beach in north-eastern

Mediterranean Turkey indicates that crab burrows were significantly more during the summer

than the autumn and the crab density decreased with distance from the sea as fewer crabs

were noticed in the subterrestrial fringe between 7.5-15m than those above the water line

(Türeli, et.al., 2009). Similar results have been produced for Ocypode cursor at Alagadi beach in

northern Cyprus by Strachan et al., (1999) who highlighted that crabs were significantly greater

in numbers during the summer than during autumn and the population was also decreasing

with distance from the sea. A similar relationship between the location of burrows and distance

from the sea was reported for Ocypode cursor from Ewa-Oboho (1993) who noticed that the

most populated area was 1-1.6m from the tidal height. From the above studies on the dispersal

pattern of crab activity it can be concluded that ghost crabs occur in areas closest to the sea

and appear more active during summer, autumn and in some cases during spring periods than

during winter. This is related to seasonal differences of ghost crabs rhythms with low activity

during cold days (Haley, 1969).

Furthermore, studies indicate differences in the sex ratios of mature male and female ghost

crabs during summer and winter as highlighted for Ocypode cursor at Alagadi beach since

during July mature male crabs were considerably more than mature female crabs (Strachan

et.al., 1999). These differences in sex ratios are probably because female crabs were residing

and remaining underground in the male burrows as has been stated for Ocypode saratan, or

may plug their burrow openings as has been noted for Ocypode ceratophthalmus (Strachan

et.al., 1999).

13

2.3.3. Effect of human activity on ghost crabs

The behaviour of ghost crabs is very flexible and complex, having very sophisticated form

(Barras, 1963; Barros, 2001). The density of ghost crabs can be reduced by human disturbance

(Hughes, 1966; Chan et. al., 2006) and crab burrow density can be used as an indicator of

human impacts on sandy ecosystems (Barros, 2001; Aheto et. al., 2011). On the contrary,

Strachan et.al., (1999) argued that in northern Cyprus human activities did not have any

negative effects on ghost crab Ocypode cursor. In contrast, ghost crabs benefited from such

activities as they were attracted from discarded food left on the beach, and beaches used by

people were amongst the ones with highest numbers of crabs.

2.3.4. Significance of burrows and their relationship with ghost crabs

Ghost crabs construct deep and complex burrows (Lucrezi et.al., 2009) which allow them to

breath air and escape from their predators (Türeli, et.al., 2009), which may not always work

(McMahon and Burggren, 1988). Burrows also protect ghost crabs from climatic extremes of

high and low temperatures (Eshky et. al., 1995) and winds. It is used as a base of living activities

such as feeding and territorial behaviour (Türeli, et.al., 2009). Burrows can be closed with a plug

allowing the crab to survive during periods of drought (McMahon and Burggren, 1988; Vannini,

1980a). Moreover, copulation typically occurs in the burrow which protects molting crabs and

females with developing eggs (Vannini, 1980a). Burrows are possibly a limited resource.

According to McMahon and Burggren, (1988), competition for burrows is due to the energy

needed to construct or the rarity of suitable sites. Many ghost crabs prefer to use an existing

burrow than to build a new one and adult crabs can force juveniles out and then enlarge and

occupy the burrow (McMahon and Burggren, 1988).

The location, shape and depth of Ocypode burrows vary according to species, age, sex and the

size of the crab (Specht, 1985; Shuchman and Warburg, 1978). Burrows are mostly found on

medium grain sand (Türeli, et.al., 2009; Strachan et.al., 1999) having one circular surface

burrow opening (Strachan et.al., 1999; Türeli et.al., 2009), surrounded by feeding lines of crabs’

tracks (Chan et. al., 2006) and inhabited by one (Barras, 1963) or even two crabs during the

copulation (McMahon and Burggren, 1988). The shape of burrows depends on the anatomy

and sex of the crab (Shuchman and Warburg, 1978; Türeli, et.al., 2009).

Many studies for Ocypode ryderi (Vannini, 1980a) and Ocypode ceratophthalmus (Jones, 1972)

revealed that male crabs always have a pile of sand just outside their burrows, while female

and juveniles just scatter the sand in all directions (Figure 9). The pyramid-shaped pile of sand

near the entrance of the burrow is created by males to attract females during the mating

season (Martin, 2006, Strachan et.al., 1999) and discourage other males from approaching their

burrows (McMahon and Burggren, 1988).

14

Figure 9: Ocypode cursor burrows of male (A) and female and juveniles (B)

(A) (B)

2.3.4.1. Orientation, slope, depth and zonation of burrows

Burrows are commonly oriented seaward (Vannini, 1980a), confirmed by studies carried out for

Ocypode cursor in north-eastern Mediterranean Turkey (Türeli, et.al., 2009) and in northern

Cyprus (Strachan et.al., 1999). The slope of the burrow depends on the weight of the crab and

the type of the substratum (Vannini, 1980a).

Sassa and Watabe (2008) reported that most Ocypode species live in burrows that do not

exceed 20cm in depth. On the contrary Türeli, et.al., (2009) and Strachan et.al., (1999) noticed

that burrows of Ocypode cursor were deeper than 20cm, reaching a depth of 60cm. Burrows

should be sufficiently deep to avoid risks such as surface transport, predators and the direct

rays of the sun (Sassa and Watabe, 2008).

The burrow diameter correlates with the size of the crab as elder crabs are generally found

further from the sea than young crabs (Shuchman and Warburg, 1978; Türeli, et.al., 2009;

Strachan et. al., 1999; Quijon et. al., 2001). Studies on Ocypode cursor burrows in north-eastern

Mediterranean Turkey (Türeli, et.al., 2009) and northern Israel (Shuchman and Warburg, 1978)

found that their diameter increased with distance from the sea. Similar to the these studies is

the study of Ocypode cursor in northern Cyprus which indicates that juveniles burrow closer to

the sea since no burrows greater than 4cm in diameter were found within the first zone located

closer to the sea, while further away from the sea very few burrows were counted with

diameter less than 1cm (Strachan et.al., 1999). However, Barras (1963) argued that the

distribution of the crabs within the zone located closer to the sea was not related to their sizes.

Similarly Türeli, et.al., (2009) assumed that during their study of Ocypode cursor carried out in

2001, small burrows were concentrated in all zones of the beach.

15

2.3.5. Relationship of ghost crabs with environmental variables

2.3.5.1. Water content

Ghost crabs cannot live in terrestrial environments where water is not available (McMahon and

Burggren, 1988). The lack of moisture can cause the loss of body weight and impair the

locomotion of ghost crabs (Weinstein, 1998). Thus, the water content of the sand is a key

factor in determining crab burrow distribution (Shuchman and Warburg, 1978; Lucrezi et.al.,

2009). Ocypode cursor chooses sand of high water content in which to burrow (McMahon and

Burggren, 1988). Previous studies from Gilad-Shuchman and Warburg (1977) found that

Ocypode cursor preferred the higher moisture alternative by digging their burrows there and

detecting differences in water content of even 1%, while in another study Shuchman and

Warburg (1978) noted that the most densely populated area was where the sand moisture was

about 14%. They argued that the preference to sand moisture depends on the moisture

alternatives available alongside with the differences between them (Warburg and Shuchman

1979).

Burrows of ghost crabs often approach the water table (Eshky et.al., 1995; Specht, 1985; Milne

and Milne, 1946). According to Strachan et al., (1999) the deepest part of the burrow is located

at least 1cm above the water table. Therefore in areas where ghost crabs live in burrows

actually lacking water, the degree of sand moisture is vital for their dispersal pattern

(Shuchman and Warburg, 1978). In many instances the depth of the burrow is correlated with

the distance from the sea, as burrow depth increased further away from the sea reflecting the

increasing depth of the water table (Strachan et.al., 1999; Türeli, et.al., 2009).

Ghost crabs, especially juveniles have high levels of evaporative water loss (Lucrezi et al., 2009).

Evaporative water loss occurs from all exposed parts of the body surface. The rate of water loss

depends on the permeability of body parts of the crab and the most permeable parts appear to

be gills and lungs because of the thin permeable surface for gas exchange (McMahon and

Burggren, 1988). There are several behavioral mechanisms to minimize water loss such as

building their burrows to reach the water table, foraging mostly during the night when the

humidity is high, becoming active just after a rainfall and entering the sea to moist their gills

(Weinstein et.al., 1994). Furthermore some Ocypode species plug their burrows before tidal

inundation to supply a pocket of air at the top of their burrows, helping them to retain sand

moisture in their burrows while oxygenating water toward the base of the burrow for gill

wetting (Martin, 2006).

16

2.3.5.2. Environmental temperatures

Members of Ocypode are susceptible to environmental temperatures, being less active at low

temperatures of about 15-20ᵒC (Rosa and Borzone, 2008; Weinstein, 1995, 1998; Milne and

Milne, 1946), and more active at about 30ᵒC (Lucrezi et. al., 2009). The thermal preference of

Ocypode cursor is between 26-29ᵒC (Gilad-Shuchman and Warburg, 1977). Eshky et.al., (1995)

assumed that as the temperature decreased, the crab activity increased as they were moving

over the sandy shore and relaxing in areas of shade. Furthermore during unfavorable conditions

such as sea storms and intense winds Ocypode species remain in their burrows with their

burrow apertures closed with sand, staying inactive for long period (Rosa and Borzone, 2008).

Very high temperatures also decrease the crab activity since they move into the shade or

remain in their burrows (Eshky et.al., 1995; McMahon and Burggren, 1988), which provide

moist and cool habitat (McMahon and Burggren, 1988), protecting them from overheating and

dehydration (Specht, 1985; Vannini, 1980a).

The time of the day can influence the activity of ghost crabs as many remain inactive during the

hottest part of the day in their burrows (Lucrezi et. al., 2009) since the temperature of crab

burrows follows the sediment column temperatures protecting Ocypode species from high

external temperatures (Strachan et.al., 1999). Also temperatures may be even lower further

deep the burrow (Chan et.al., 2006) as in the case of Ocypode cursor in northern Cyprus where

sediment column temperature at 12.00h was lower that both air and sand surface

temperatures and as the sediment column was taken from points further deeper from the sand

surface, the temperature decreased (Strachan et.al., 1999). A similar observation was made for

Ocypode cursor in north-eastern Mediterranean Turkey where sediment column temperature

taken from a depth of 40cm was lower than those taken from shallower depths (Türeli et.al.,

2009).

17

3. Study Rationale

The extensive and critical review of the academic literature describes a range of aspects about

the behaviour and ecology of ghost crab Ocypode cursor (L.). Within the Mediterranean this

species is found on east and central Mediterranean beaches (Türeli et.al., 2009). Nocturnal

activity prevails for Ocypode cursor although it can be seen active during all hours of the day

(Section 2.2.) and appears to be more active during warmer periods (Section 2.3.2.). The

distribution and abundance of Ocypode cursor is influenced by human activities to some extent

(Section 2.3.3.), and highly depends on ecological variables (Sections 2.3.4, 2.3.4.1. and 2.3.5.)

The area of Akrotiri Peninsula (Sections 4.2. and 5.1.1.) is an appropriate location to study the

distribution of Ocypode cursor (L.) and its relationship with ecological variables as it supports a

large population of ghost crabs. Any effect of human activities could be easily examined along

the study area by comparing the undisturbed and disturbed sites.

3.1. Research aims

The purpose of this study is to examine the distribution of Ocypode cursor along the East coast

of Akrotiri Peninsula in Cyprus during the summer period alongside with its relationship with

ecological variables and human activities.

Therefore the central aims of this study are to investigate if the dispersal pattern of Ocypode

cursor changes through the different periods of the summer which are June, July and August.

Moreover, the relationship of Ocypode cursor with ecological variables including water,

environmental/sand temperatures and sand granulometry will be established along the study

area. Ultimately, any effects of human activities on Ocypode cursor will be investigated since

one section of the study area is stated as an undisturbed beach while the other section is stated

as a disturbed beach.

18

In order to achieve the aims, the following research questions have been devised:

What is the distribution of ghost crab Ocypode cursor along the study area during

different periods of the summer?

How do human activities affect the density of Ocypode cursor population in the study

area?

How does the burrow density and diameter vary with distance from the beach, air and

sand temperatures, sediment column, moisture content and sand granulometry in the

study area?

The aims of this study together with observations involved within the literature review lead to

the growth of six hypotheses for examination which are critical for the study of Ocypode cursor

in Cyprus, helping answer the research questions of this project.

Hypothesis 1: ‘The highest activity of Ocypode cursor takes place during warm months.’

Hypothesis 2: ‘Ocypode cursor can benefit from human activities such as discarded food but it

may also be negatively affected by recreational activities.’

Hypothesis 3: ‘Ocypode cursor highly depends on water. Burrow density decreases away from

the sea.’

Hypothesis 4: ‘Sediment temperatures are crucial to the distribution of Ocypode cursor.’

Hypothesis 5: ‘Ocypode cursor highly depends on sand moisture. Juveniles are found closer to

the sea while adults are found further landwards.’

Hypothesis 6: ‘The densities of Ocypode cursor burrows are higher in medium grain sand.’

19

4. Selection of study area

4.1. Island of Cyprus

The selection of the location for this project is based on the evidence that Ocypode cursor is

copious in Cyprus. There is no overall study for the distribution of Ocypode cursor in Cyprus, but

specific studies show that it can be found on Lara beach in Paphos (Alfonso et.al., 2007), on

Lady’s mile beach in Limassol (personal observation) and on Alagadi turtle beach in Kyrenia

(Strachan et.al. 1999)(Figure 11).

Cyprus is the Easternmost island of the Mediterranean at the crossroad of Asia, Europe and

Africa (EEA, 2010) (Figure 10). It is the third largest Mediterranean island after Sicily and

Sardinia (Button, 2010), with an area of 9,251km2 (IUCN, 2012) and a coastline of 648km

(Encyclopedia of the nations, 2013).

Cyprus has a typical Mediterranean climate with hot and dry summers (IUCN, 2012) with air

temperatures regularly in the low to mid 40ᵒC, while winters are cool, seldom wet and cold,

with an average annual rainfall of 450-600mm (Button, 2010).

Cyprus has been described as ‘the biodiversity hotspot’ of the Mediterranean Basin because of

its large diversity of fauna, flora and distinct mosaic biotopes (EEA, 2012; IUCN, 2012).

Figure 10: Location of Cyprus in the Eastern Mediterranean Sea

(Modified version of Button, 2010)

20

Figure 11: Distribution of Ocypode cursor (L.) in Lara beach (A), Lady’s mile beach (B) and

Alagadi beach (C) in Cyprus

(Adapted from NASA Earth Observatory, 2001)

21

4.2. Akrotiri Peninsula

4.2.1. Location

Akrotiri Peninsula is chosen for this project as it supports a large number of ghost crabs

Ocypode cursor.

It is located at the southernmost part of Cyprus (Charilaou et.al., 2012) (Figure 12). Akrotiri

Peninsula covers about 60km2, including a Southern plateau with a maximum elevation of 60m.

The northern part of Akrotiri lies below 10m elevation and is covered by alluvial deposits. In the

middle area of Akrotiri there is the Salt Lake, which lies below the sea level with a minimum

elevation of -2.7m (Figure 13). The Southern and Western coasts are exposed to winds, while

the Eastern part is sheltered most of the time (Charilaou et.al., 2012).

Most area of Akrotiri is situated within the Sovereign Base Area of Akrotiri and is only a few

kilometers to the Southwest of the rapidly developing city of Limassol (Charilaou et.al., 2012).

Figure 12: Location of Akrotiri Peninsula in Cyprus

(Google maps, 2013)

Salt Lake

22

Figure 13: Salt Lake of Akrotiri Peninsula

(Charilaou et.al., 2012)

4.2.2. Environmental importance

Cyprus is on one of the key migratory routes for birds and Akrotiri Peninsula is a significant

station of this route (AEEIC, n.d). Akrotiri wetlands is the greatest aquatic system in Cyprus and

one of the very few main Salt Lakes within the Eastern Mediterranean in semi-natural condition

with significant biodiversity and ecological value (Charilaou et.al., 2012). It is one of the most

significant biodiversity hotspots in Cyprus because of its unique combination of factors such as

the location and geomorphology, diverse hydrology and semi-natural condition of its habitats

(Charilaou et.al., 2012).

Akrotiri peninsula is a unique area in Cyprus, having 29 different types of habitats out of which

26 are included in Schedule 1 to the Protection and Management of Nature and Wildlife

Ordinance, which support many vulnerable, rare and endangered plant and animal species

which are crucial in preserving the biological diversity of the eastern Mediterranean region

(Charilaou et.al., 2012).

Moreover, 260 species of birds have been recorded in the peninsula out of 370 in the whole of

Cyprus. Roughly 200 of these are migratory and together with resident bird species find

essential feeding, resting and breeding habitat at Akrotiri (Charilaou et.al., 2012). Moreover,

more than 90 bird species are included in Schedule 1 to the Game and Wild Birds Ordinance.

(Charilaou et.al., 2012)

Akrotiri Peninsula is also a nesting area for the two species of the marine turtles - the green

Chelonia mydas and loggerhead Caretta caretta - which are both in danger for disappearance in

23

the Mediterranean (Charilaou et.al., 2012). The peninsula provides also habitat for significant

species of mammals including dolphins, seals and bats, dozens of insects with 77 endemic and

other significant types and 9 endemic species of snails (AEEIC, n.d).

Akrotiri Peninsula is a significant botanical hotspot in Cyprus because more than 800 indigenous

plant taxa were recorded in the peninsula out of around 2000 in the whole of Cyprus, with 32

listed in the Red Book of Cypriot Flora (AEEIC, n.d; Charilaou et.al., 2012).

Akrotiri Peninsula was declared an Important Bird Area by ‘Birdlife International’ and had been

recognized by many other International Conventions including the ‘Convention of Bern’ for the

preservation of natural ecotopes and wildlife, the ‘Convention of Bonn’ for the preservation of

migrating species of wild fauna and the ‘Convention of Barcelona’ for the protection of coastal

regions and marine environments of the Mediterranean (AEEIC, n.d).

Big parts of the peninsula have been designated as a Special Protection Area (SPA) for birds and

a Ramsar site by the Sovereign Base Areas Administration and the whole peninsula is a

candidate Special Area of Conservation (Charilaou et.al., 2012).

Despite its protection regime, it is under increasing threats from human activities because of

the physiology and topography of the area (muddy areas, sand flats and sand dunes). Off road

driving is a very common phenomenon between the Salt Lake and the Lady’s mile coast

affecting wildlife (Figure 14). Further problems affecting animal populations include parking,

raking of the sand and development aspirations (Charilaou et.al., 2012).

Figure 14: Major areas of off-road racing

(Charilaou et.al., 2012)

24

5. Methods and Materials

In order to test the hypotheses and to achieve the research aims (Chapter 3), a suitable

methodology was devised.

5.1. Fieldwork methods

5.1.1. Study area

The distribution of Ocypode cursor (L.) was studied on the sandy beach of the east coast of

Akrotiri Peninsula in Cyprus which supports a large population of Ocypode cursor.

The study area was first divided into two sites (Figure 15). The first site is the southern part

where the fenced RAF Akrotiri is located. This part of the peninsula is used by British Military as

an airbase (Charilaou et.al., 2012). This section of the beach is undisturbed with no or relatively

low presence of people as access is restricted. Moreover this area of the beach is a nesting

place for both Green (Chelonia mydas) and Loggerhead (Caretta-Caretta) turtles (AEEIC, n.d)

(Figure 16).

The second site is the northern part and is the area known as Lady’s mile beach. Lady’s mile

beach is located to the Southwest of the city of Limassol, on the Akrotiri Peninsula, which is the

second biggest and the most rapidly developing city in Cyprus (Charilaou et.al., 2012). It is 7km

long and stretches down the East coast of Akrotiri Peninsula from Limassol port to the RAF

base. Lady’s mile is a disturbed beach having a very high presence of people especially during

the daytime in the summer as it is freely accessible to the public. Thousands of families take an

advantage of warm summer days spending time with their children in the blue waters of Lady’s

mile beach. Many organized summer schools bring children there to spend the morning playing

a variety of beach games and sports. It is a heavily recreational beach consisting of many cafes

and restaurants which attract many visitors. The increasing demand has led cafe and restaurant

owners to illegally extend their parking areas against protected habitats (Figure 17). Many

restaurants have also illegally extended their working hours, altering the use from beach cafes

to night clubs (Charilaou et.al., 2012).

25

Figure 15: Study area of the East coast of Akrotiri Peninsula

(Google maps, 2013)

26

Figure 16: Turtle nesting sites at Akrotiri Peninsula

(Charilaou et.al., 2012)

Figure 17: Parking areas at Lady’s mile beach

(Charilaou et.al., 2012)

27

5.1.2. Preparation of the study area

The study area of Akrotiri Peninsula consists of many gravelly sections in addition to sandy

parts. Ocypode cursor has its mouth parts adapted for feeding only upon sandy substratum

(Ewa-Oboho, 1993). Thus, the gravelly parts of the beach were excluded from the study area as

they did not support any ghost crab population. These areas were marked using Global

Positioning System (GPS) and were excluded from the survey (Table 3).

Then an appropriate number of plots representing 10% of the total study beach length of each

site (northern, southern) (about 5km) were selected randomly as being suitable for crab

burrows. These areas were marked using GPS and were plotted on a map and studied during

the summer. Plots 1-6 are located on the southern site whilst plots 7-15 on the northern site of

the study area (Figure 18).

All 15 plots had a length of 20m but the width was variable extending from the waterline back

to the shore where crab burrows stopped occurring and vegetation began. The study plots are

shown in Figure 19 and their dimensions are given in Table 3 below. At the back end of each

plot, 4 pink ribbons were tied on branches of plants for easy identification of the plots.

Table 3: Grid values and Dimension zones of plots

Plots Grid Values Dimension Zones (length ×width) (m)

1 502468/3827375 20 5

2 502256/3826476 20 10

3 501516/3827242 20 5

4 501221/3827707 20 10

5 500730/3828309 20 10

6 500719/3828346 20 10

7 500708/3828394 20 15

8 500641/3828784 20 20

9 500581/3829295 20 30

10 500569/3829444 20 10

11 500550/3829639 20 10

12 500534/3830007 20 15

13 500535/3830200 20 10

14 500532/3830392 20 10

15 500540/3806000 20 15

28

Figure 18: Location of plots along the study area of Akrotiri Peninsula

(Google maps, 2013)

29

Figure 19: Pictures of plots

Plot 1 Plot 2

Plot 3 Plot 4

Plot 5 Plot 6

30

Plot 7 Plot 8

Plot 9 Plot 10

Plot 11 Plot 12

31

Plot 13 Plot 14

Plot 15

32

5.1.3 Determination of the temporal and spatial distribution, size frequency and burrow

density of ghost crab

In order to determine the population of Ocypode cursor, it was assumed that the number of

burrows present on the beach was the same as the number of ghost crabs Ocypode cursor

(Türeli et.al., 2009; Valero-Pacheco, et.al., 2007). The distribution of Ocypode cursor is

estimated mainly by counting its active burrows (Lucrezi et al., 2009). The top of crab burrows

on the sand are visible holes and therefore counting burrow entrances on the beach surface

was a useful tool to measure the population densities of Ocypode cursor (Lucrezi et.al., 2009).

For the distribution of Ocypode cursor, the total number of burrows in each plot within the

study area was recorded in June, July and August. During each month four counts of the total

number of burrows were taken early in the morning during seven day intervals. The counts

were made at this time of the day because crabs excavate new burrows or repair the old ones

early in the morning, while during the heat of the day they may plug their burrows (Hobbs

et.al., 2008; Moss and McPhee, 2006).

For the size frequency, the diameter of each crab burrow-openings was measured using Vernier

callipers and was assigned into one of the six size classes (<10mm, 10-19mm, 20-29mm, 30-

39mm, 40-49mm and >50mm). The distance of each burrow from the sea in each plot was also

measured using a tape to investigate the relationship between burrow density and distance

from the sea.

5.1.3.1. Data analysis

Data were collected to analyze the temporal and spatial distribution of Ocypode cursor during

the different periods of the summer. Results of data were used to show the total numbers of

burrows recorded for each week, for each month and along the study area during the study

period. Moreover results from data were used to compare the percentage of the average

number of burrows found in the southern and in the northern site of the study area. An

asymmetrical analysis of variance (ANOVA) was used to test differences in the number of

burrows during the three-month study period. The Mann Whitney test was used to test

differences in the number of burrows between the two sites of the study area.

For the size frequency distribution of burrows data were collected and used to show the

distribution of each size class found in each plot and the percentage number of each size class

during the study period. To test the prediction that burrow densities vary with distance from

the sea, data were collected to show the percentage and the total distribution of burrow

numbers found across the beach zones as well as the distribution of burrows in each beach

zone of each plot during the study period. A Two-Sample T-Test was used to test differences in

the number of burrows found in different zones of the beach. To test the relationship between

33

burrow diameters and distance from the sea data were collected to show the size frequency

distribution in relation with distance from the sea (every 2m) as well as the size frequency

distribution found in each zone of the beach. Results of these data were used to show the

percentage of each size class found in each beach zone of the study area.

Zones of the beach are shown in Appendix 2.

5.1.4. Determination of human disturbance

Human activities include high presence of people who can pollute and have an impact on the

beach in many ways (discarded food/litter, trampling, excavation, off-road vehicles, sand

raking). Both these impacts and beach management (cafes/restaurants, beach games/sports)

are important factors that affect the distribution of ghost crabs as has been described already

in similar studies (Aheto et.al., 2011; Barros, 2001; Steiner and Leatherman, 1981).

In order to estimate human disturbance within the study area, a scale of 0-5 was used to

describe human activities in each plot where 0=No human activity and 5=Very high human

activity (Appendix 1). During each month four recordings of human activities were made during

seven day intervals.

5.1.4.1 Data analysis

Data were collected to show the average scale of recordings for human disturbance during the

study period as well as in each plot for each month. The Kruskal-Wallis test was used to test

differences of the average numbers of human disturbance during the three-month study

period. Moreover results of data were used to compare the percentage of the average scale of

human disturbance between the two sites of the study area. The Mann Whitney test was used

to test differences of the average numbers human disturbance between the two sites. To test

the assumption that human disturbance affects crab populations the Person’s Correlation was

used to test the relationship between burrow numbers and human disturbance.

34

5.1.5. Determination of environmental temperatures

Environmental temperatures include air, sand surface and sediment column. Environmental

temperatures were recorded at regular intervals every six hours (06.00h, 12.00h, 18.00h,

00.00h) once a month using a portable digital temperature probe.

Sediment column temperature was recorded at a depth of 25cm, assuming this depth for the

burrows.

Sand surface and sediment column temperatures were recorded from each zone of the beach

(every 5m intervals starting from the middle of the plot’s width from the water line back to the

shore) (Appendix 2) to test if sand temperatures change widthwise.

It has to be mentioned that environmental temperatures of plots recorded in June were almost

the same lengthwise of the beach but different widthwise (personal observation). Thus

environmental temperatures did not change lengthwise but only widthwise. Due to this

observation, environmental temperatures were taken only from the longer plot of the study

area which was plot 9 (30m).

5.1.5.1. Data analysis

Data were collected to show how environmental temperatures change during the different

periods of the summer across the zones of the beach of the study area. Results of data were

used to test if environmental temperatures are crucial for the distribution of Ocypode cursor,

affecting their burrow density and diameter.

5.1.6. Determination of moisture content of the sand

The sand moisture of each plot was recorded once a month. Sand samples of 200g were taken

from the sand surface of each plot to a depth of 25cm. Sand moisture was also recorded from

each zone of the beach (Appendix 2) to test if the moisture content of the sand changes

widthwise of the beach.

Each sand sample was weighed on an EXCEL KG/LB kg3 div. 1 gr., when the sand was moist.

Then each sand sample was dried to remove any moisture in an oven at 110ᵒC for a 24hour

period and was weighed again.

5.1.6.1. Data analysis

Data were collected to show if sand moisture changes during the study period across the zones

of the beach of the study area. Results were used to test the prediction that the sand moisture

is crucial for Ocypode cursor, affecting their burrow density and diameter.

35

To find the sand moisture of each plot, the percentage of sand moisture content was calculated

using the following formula:

where Ww is the wet sand weight and Wd is the dry sand weight (Shuchman and Warburg,

1978).

5.1.7. Determination of sand granulometry

The sand granulometry of each plot was recorded once a month. Sand samples of 100g were

taken from the sand surface of each plot to a depth of 30cm using a shovel, from each zone of

the beach (Appendix 2) to test the granulometric characteristics of the beach.

Each sand sample was weighed on an EXCEL KG/LB kg3 div. 1gr., and then it was dried in an

oven 110ᵒC for a 24hour period to remove any moisture and avoid sticking on the sieve.

5.1.7.1. Sieving and calculation of sand samples

The total amount of each sand sample was weighed and sieved using Endecott sieves. To find

the percentage of aggregate passing through each sieve and therefore the grain size of each

sand sample, the percent retained in each sieve was found using the following formula:

% Retained =

where Wsieve is the weight of aggregate in each sieve and Wtotal is the total weight of the

aggregate (Pavement Interactive, 2011)

The next step was to find the cumulative percent of aggregate retained in each sieve. This was

found by adding up the total amount of aggregate that was retained in each sieve and the

amount of aggregate in the previous sieves.

Then the cumulative percent passing of the aggregate was found by subtracting the percentage

retained from 100% as follow:

%Cumulative Passing = 100 % %Cumulative Retained (Pavement Interactive, 2011) (Appendix

3).

36

5.1.7.2 Data analysis

Data were collected to show if the grain size changes across the zones of the beach and to test

the prediction if different size grain of the beach is critical for Ocypode cursor. Results of data

were used to show whether the size grain of the beach affects the burrow density and diameter

of the crab. Also the Mann Whitney test was used to test differences in burrow numbers found

in coarse and medium sand grain.

Each sieve represents a specific number which refers to the opening millimeters size of that

sieve (Table 4).

To find the grain size distribution of each sand sample, the base two logarithmic (phi) scale

was used (Pfannkuch and Paulson, n.d.) (Table 4).

The base two logarithmic phi values were calculated from particle diameter size measures in

millimeters as follow:

=

where is the particle size in units and d is the diameter of particle in millimeters

(Pfannkuch and Paulson, n.d.).

Table 4: Particle diameter size and logarithmic phi values of each sieve

Number of sieves Particle diameter size (mm) Logarithmic phi ( ) values

No. 10 2 -1

No. 20 0.85 0.23

No. 30 0.6 0.74

No. 40 0.42 1.25

No. 60 0.25 2

No. 80 0.18 2.47

No. 100 0.15 0.3

No. 120 0.125 0.38

No. 250 0.06 0.7

37

Then the cumulative weight percent retained and cumulative weight percentage passing in

each sieve were plotted on a graph where in one of the curve (cumulative weight percent

passing) the fraction that is finer than each subsequent grain size was shown, while in the other

curve (cumulative weight percent retained) the fraction that is coarser than each subsequent

grain size was shown (Pfannkuch and Paulson, n.d.).

Then the grain size distribution was found using the following formula:

GMz =

where GMz is the geometric mean size, is the average size of the coarsest third of the

sample, is the average of the middle third of the sample and is the average size of the

finest third of the sample (Folk and Ward, 1957).

Then using the Median grain ( ) which the phi size corresponding to the 50% mark ( ) on the

cumulative frequency distribution curve, the grain size of each plot was found according to

Pfannkuch and Paulson,( n.d.) (Appendix 4).

38

5.1.8. Limitations

The research methods used to complete this survey involved six limitations as discussed in Box

1 below.

Box 1: Key limitations of the research methods employed in this survey

Key limitations

The determination of the spatial distribution of Ocypode cursor by counting its active burrows might

not be accurate since a single burrow could include two crabs as discussed in Section 2.3.4. Also

some active burrows could have been plugged by the crabs or by human trampling making them

undetectable.

Plots did not have the same dimensions creating a possible bias between the ones extending away

from the sea and the ones not.

It was not possible to take the temperatures from all plots quickly so as to keep within the preset

hours.

Sediment column temperatures were only taken to a depth of 25cm. Therefore temperatures might

be even lower in deeper depths (as discussed in Section 2.3.5.2.).

The collection of sand samples for the study of the sand moisture was a difficult task and was

subject to many errors due to the small moisture contents and the accuracy of measuring the weight

etc.

The grain size within certain plots was variable, which makes analysis more complicated.

39

6. Results and Analysis

6.1. Temporal and spatial distribution, size frequency and burrow density of ghost crab

The numbers of burrows found each week in each plot are shown in Appendix 5. The total

numbers recorded in all plots during June, July and August were 89, 103 and 85 respectively

(Figure 20) and there was no significant difference between them (ANOVA F=0.10, P=0.905).

Although the number of burrows counted each week as shown in Figure 21 varied up and

down, there is no consistent trend in these variations.

The number of burrows counted in each plot each week, adjusted to account for the fact that

the plots did not have the same area, by extrapolation to 600m2, is shown in Appendix 6. The

adjusted burrow numbers are plotted in Figure 22 below. As can be seen from this figure, the

burrow observations during the study period covered all 15 plots. Burrows were counted from

most of the plots during June (from 14 plots) and July (from 13 plots) while in August burrows

were absent from 6 plots. The greatest counts were in plots 6 (180 burrows), 4 (171) and 5

(162) all of which are located in the southern site. However the rest of the southern plots (plots

1, 2 and 3) had low numbers: 1 had 30, 2 had 3 and 3 had 30. Also, all the plots in the northern

site were relatively low in burrow numbers (Figure 23). The percentage of average number of

burrows in the southern site was 84% compared to 16% in the northern site as seen in Figure

24 below. There was also a significant difference between the number of burrows in the plots

of the southern site and those of the northern site (Mann Whitney W=62.0, P=0.1116). The

difference between the average number of burrows in the southern and the northern site was

high in each month: in June it was 76% compared to 24%, in July 84% compared to 16% and in

August 91% compared to 9% (Figure 25).

The frequency of burrows in different size classes during the whole period in all plots was also

analysed. The most frequent size classes were those of 30-39mm (34%), followed by 20-29mm

(33%), 40-49mm (19%), 10-19mm (7%), >50mm (7%) and <10mm (0%) as shown in Figure 26

below. As can be seen in Figure 27, the distribution of size classes was similar for each month

and close to a normal distribution. The distribution of different size classes in each plot is

shown in Figure 28 below.

A simple calculation of the average number of burrows at 5m, 10m, 15m, 20m, 25m and 30m

shows that most burrows are within the 0-5m (39%) and 5-10m (27%) while it is less in the rest

zones of the beach (Figures 29, 30). However there is a bias in this calculation, as plots 4, 5, 6

which had the highest number of burrows of all plots (as discussed above) extended only to

10m, thus pushing the average of 5m and 10m up. Therefore, in order to compare between the

three first zones (5, 10, 15m), only the numbers of burrows in the plots that extended to at

least 15m (plots 7, 8, 9, 12 and 15) were subsequently considered, yielding an average number

of 2.07 burrows for the 5m, 3.40 for 10m and 1.07 for 15m (Appendix 7). Thus, there is a clear

decrease of the numbers for 15m compared to the ones for 5 and 10m. A statistical t-test

40

between 0-5 and 10-15m (T-Value=1.33, P-Value=0.197, DF=21) and 5-10 and 10-15m (T-

Value=1.38, P-Value=0.182, DF=19) shows that the differences have some, but not very high

statistical significance. The number of burrows in each plot in each zone of the beach is shown

in Figure 31 below.

Figure 32 shows the number of burrows from each size class every 2m from the sea for each

month. This suggests that in June the most populated area was between 6-8m from the sea, in

July between 2-10m from the sea and in August between 4-6m from the sea, showing a

preference area of Ocypode cursor at 6m. However, it should be mentioned that the bias

discussed above in respect of the limited extent to 10m of plots 4, 5 and 6 applies here as well.

An interesting correlation was noticed between the size of burrows and the distance from the

sea, as burrow diameters increased with distance from the sea (Figure 33, 34). Although this

correlation is not very strong, it is quite clear. The single observation of less than 10mm

diameter was in 0-5m, 95% of the 10-19mm observations were at 0-5m and the remaining 5%

at 5-10m. For the 20-29mm, 57% were at 0-5m, 27% at 5-10m whereas the rest extended up to

30m. For the 30-39mm class, 52% were at 0-5m and 36% at 5-10m while the rest extended up

to 30m. For the 40-49mm class, 43% were at 0-5m, 37% at 5-10m, 13% at 10-15m and the rest

extended to 25m. For bigger than 50mm, 28% were at 0-5 m, 39% at 5-10m, 5% at 10-15m and

28% at 25-30m. This shows a clear trend for distribution of bigger diameter burrows further

away from the sea. However it is also evident that areas closer to the sea were inhabited from

all size classes as shown in Figures 32, 33, 34.

Figure 20: The temporal distribution of Ocypode cursor along the East coast of Akrotiri

Peninsula during the study period

0

20

40

60

80

100

120

June July August

Nu

mb

er

of

Bu

rro

ws

Months

Series1 Ocypode cursor

41

Figure 21: Weekly recordings of Ocypode cursor burrows along the study area during the study

period

Figure 22: Burrow numbers of Ocypode cursor along the study area of Akrotiri Peninsula during

the study period

0

5

10

15

20

25

30

1 2 3 4 5 6 7 8 9 10 11 12

Nu

mb

er

of

Bu

rro

ws

Weeks

Series1 Ocypode cursor

0

10

20

30

40

50

60

70

80

90

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Nu

mb

er

of

Bu

rro

ws

Plots

June

July

August

Months

42

Figure 23: Ranking order of plots according to the highest number of Ocypode cursor burrows

during the study period

Figure 24: Percentage of the average number of burrows of the southern and the northern site

of the study area during the study period

0

20

40

60

80

100

120

140

160

180

200

Nu

mb

er

of

Bu

rro

ws

Plots

Series1

6 4 5 15 9 1 3 7 13 12 14 8 10 11 2

84%

16%

1

2

South North

Sites of the Beach

Ocypode

cursor

43

Figure 25: Percentage of the average number of burrows of the southern and northern site of

the study area during June (A), July (B) and August (C)

(A) (B) (C)

Figure 26: Percentage of Ocypode cursor burrows belonging to each of the six size classes

recorded along the study area during the study period

76%

24% 1

2

South North

84%

16% 1

2

South North

91%

9%

1

2

South North

0%

7%

33%

34%

19%

7%

<10 <10 10-19 20-29 30-39 40-49 >50

Sizes (mm)

44

Figure 27: Size frequency distribution for the diameter of the burrow openings of Ocypode

cursor recorded along the study area during the study period

Figure 28: Size frequency distribution of the diameter of the burrow openings of Ocypode

cursor along the study area during June (A), July (B) and August (C)

(A)

-10

-5

0

5

10

15

20

25

30

35

40

<10 10 19 20-29 30-39 40-49 >50

Nu

mb

er

of

Bu

rro

ws

Burrow Diameters (mm)

June

July

August

Poly. (June)

Poly. (July)

Poly. (August)

Months

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Nu

mb

er

of

Bu

rro

ws

Plots

>50

40-49

30-39

20-29

10 19

<10

Sizes (mm)

-

-

45

(B)

(C)

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Nu

mb

er

of

Bu

rro

ws

Plots

>50

40-49

30-39

20-29

10 19

<10

Sizes (mm)

0

5

10

15

20

25

30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Nu

mb

er

of

Bu

rro

ws

Plots

>50

40-49

30-39

20-29

10 19

<10

Sizes (mm)

-

-

46

Figure 29: Burrow numbers of Ocypode cursor across the zones of the study area during the

study period

Figure 30: Percentage of the average number of burrows of Ocypode cursor across the zones of

the study area during the study period

0

20

40

60

80

100

120

140

160

180

5 10 15 20 25 30

Nu

mb

er

of

Bu

rro

ws

Zones (m)

June

July

August

39%

27%

4%

4%

15%

11%

1

2

3

4

5

6

5 10 15 20 25 30

Zones (m)

Months

47

Figure 31: Burrow numbers of Ocypode cursor along the study area across the zones of the

beach during June (A), July (B) and August (C)

(A)

(B)

(C)

0

10

20

30

40

50

60

70

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Nu

mb

er

of

Bu

rro

ws

Plots

30

25

20

15

10

5

0

10

20

30

40

50

60

70

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Nu

mb

er

of

Bu

rro

ws

Plots

30

25

20

15

10

5

Zones (m)

0

10

20

30

40

50

60

70

80

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Nu

mb

er

of

Bu

rro

ws

Plots

30

25

20

15

10

5

Zones (m)

Zones

(m)

48

Figure 32: Burrow density and diameter of Ocypode cursor with distance from the sea of the

study area during June (A), July (B) and August (C)

(A)

(B)

(C)

0

5

10

15

20

25

30

35

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Nu

mb

er

of

Bu

rro

ws

Distance From the Sea (m)

>50

40-49

30-39

20-29

10 19

<10

Sizes (mm)

0

5

10

15

20

25

30

35

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Nu

mb

er

of

Bu

rro

ws

Distance From the Sea (m)

>50

40-49

30-39

20-29

10 19

<10

Sizes(mm)

0

5

10

15

20

25

30

35

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Nu

mb

er

of

Bu

rro

ws

Distance From the Sea (m)

>50

40-49

30-39

20-29

10 19

<10

Sizes(mm)

-

-

-

49

Figure 33: Burrow density and diameter of Ocypode cursor recorded across the zones of the

study area during June (A), July (B) and August (C)

(A)

(B)

(C)

0

5

10

15

20

25

30

35

40

45

5 10 15 20 25 30

Nu

mb

er

of

Bu

rro

ws

Zones (m)

>50

40-49

30-39

20-29

10 19

<10

Sizes(mm)

0

10

20

30

40

50

60

5 10 15 20 25 30

Nu

mb

er

of

Bu

rro

ws

Zones (m)

>50

40-49

30-39

20-29

10 19

<10

Sizes(mm)

0

10

20

30

40

50

60

5 10 15 20 25 30

Nu

mb

er

of

Bu

rro

ws

Zones (m)

>50

40-49

30-39

20-29

10 19

<10

Sizes(mm)

-

-

-

50

Figure 34: Percentage of the average number of Ocypode cursor burrows size classes recorded

across the zones of the beach during the study period

0

20

40

60

80

100

120

1 2 3 4 5 6

Nu

mb

er

of

Bu

rro

ws

(%)

Zones (m)

Series1 <10

5 10 15 20 25 30

Size (mm)

0

20

40

60

80

100

1 2 3 4 5 6

Nu

mb

er

of

Bu

rro

ws

(%)

Zones (m)

Series1

5 10 15 20 25 30

10-19

Size (mm)

0

10

20

30

40

50

60

1 2 3 4 5 6

Nu

mb

er

of

Bu

rro

ws

(%)

Zones (m)

Series1

Size (mm)

20-29

5 10 15 20 25 30 0

10

20

30

40

50

60

1 2 3 4 5 6

Nu

mb

er

of

Bu

rro

ws

(%)

Zones (m)

Series1

5 10 15 20 25 30

Size (mm)

30-39

0

10

20

30

40

50

1 2 3 4 5 6

Nu

mb

er

of

Bu

rro

ws

(%)

Zones (m)

Series1

Size (mm)

40-49

5 10 15 20 25 30

0

10

20

30

40

50

1 2 3 4 5 6 Nu

mb

er

of

Bu

rro

ws

(%)

Zones (m)

Series1

5 10 15 20 25 30

Size (mm)

>50

51

6.2 Human disturbance

The average human disturbance in June in terms of the disturbance scale was 28.5, in July 30.5

and in August 26.25 as shown in Figure 35 below, which did not vary significantly (Kruskal-

Wallis H=2.00, DF=2, P=0.368).

The average human disturbance on the northern site was 95% compared to 5% on the southern

site (Figure 36), showing a significant difference between the two sites of the beach (Mann

Whitney W=6.0, P=0.0809). Human disturbance in each plot during the study period is shown in

Figure 37. The most disturbed plots were those located on the northern site of the beach while

the most undisturbed were on the southern site as shown in Figure 38. The most disturbed plot

was plot 14 since it was located just next to the restaurant where beach sports and games were

carried out (Figure 19), while the most undisturbed plots were 1 to 6 since they were located in

the southern site of the beach where the human activities were restricted (Figure 38).

There is a strong correlation between burrow density and human disturbance during the study

period due to the strong negative relationship and significant difference between the number

of burrows and human disturbance (Pearson’s Correlation = -0.374, P=0.000). The number of

burrows was considerably lower on the northern site of the beach where the disturbance was

high while in the southern site where the disturbance was low, burrow counts were

significantly greater (Figures 23, 38).

Burrow counts were at the greatest peak at plots 4, 5 and 6 during the three months (Figure 23)

where the human disturbance was significantly low (Figure 38). In contrast, recordings of

burrows at plots 10 to 14 were observed remarkably low throughout the study period (Figure

23) where human activities were considerably high (Figure 38). However, even though human

disturbance was remarkably low in plots 1, 2 and 3 (Figure 38), burrow density in these plots

was relatively low (Figure 23).

52

Figure 35: Average scale of human disturbance during the study period

Figure 36: Percentage of the average scale of human disturbance between the two sites of the

study area during the study period

24

25

26

27

28

29

30

31

June July August

Av

era

ge

Dis

turb

an

ce

Months

Series1 Human disturbance

5%

95%

1

2

Sites of the Beach

South

North

53

Figure 37: Scale of human disturbance along the study area of Akrotiri Peninsula during

different periods of the summer

Figure 38: Ranking order of plots according to the highest human disturbance during the study

period

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Sca

le

Plots

June

July

August

Months

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

Dis

turb

an

ce S

cale

Plots

Series1

14 15 12 13 11 10 9 8 7 6 5 3 4 2 1

Human

disturbance

54

6.3. Environmental temperatures

The analytical temperatures recorded from plot 9 are given in Table 5 below.

The highest average air temperature between the different times of the day was in July (32.8ᵒC)

followed by June (31.1ᵒC) and August (28.7ᵒC) (Figure 39). The average temperature of the sand

surface of beach zones between the different times of the day in July varied between 27.9ᵒC

and 46.1ᵒC, in June 23.5ᵒC - 42.1ᵒC and August 24.6ᵒC - 39.4ᵒC (Figure 40). The average

temperatures of the sediment column of beach zones between the different times of the day

was considerably lower than that of the sand surface since in June the average temperature of

sediment column varied between 28.5ᵒC and 30.2ᵒC, in July 31ᵒC - 34.4ᵒC and in August 29.6ᵒC -

31.8ᵒC (Figure 41). Also both sediment column temperatures and sand surface temperatures

remained relatively constant across the zones of the beach during each month (Figure 42).

At 12.00h, the air and sand surface were at the highest temperature point as shown in Table 5

and Figure 40 below, while sediment column was at the highest temperature point in the

afternoon at 18.00h as shown in Figure 41 below. Also, at 12.00h sediment column

temperatures were lower than the outside air and sand surface temperatures while at all other

hours (06.00h, 18.00h and 00.00h), sediment column temperatures were higher that the sand

surface temperatures (Table 5, Figures 40, 41).

There was no significant correlation between burrow density and diameter of Ocypode cursor

and environmental temperatures. However the only observation that can be made is that in the

densest areas of crab burrows (0-10m) (Figures 29, 30) the sand surface and sediment column

temperatures ranged from 22ᵒC to 46ᵒC and from 27.2ᵒC to 36ᵒC respectively (Table 5).

55

Table 5: Environmental temperatures taken at 6h intervals through a 24h period during June

(A), July (B) and August (C) from beach zones of plot 9

(A) SAND SURFACE (ᵒC)

AIR (ᵒC) TIMES (h) 5m 10m 15m 20m 25m 30m

24 41 06.00 12.00 22 35.1 22 43 26 42.5 23.5 43 24 44 24 45

33.5 26.1 18.00 00.00 32.9 26 35 26 34 29.5 34 26 33.2 26 33.5 26.2

SEDIMENT COLUMN (ᵒC) 5m 10m 15m 20m 25m 30m

06.00 12.00 27.2 29 31 29 31 29.5 27.5 29 27.5 29 27.2 29

18.00 00.00 29.9 29 30 29.5 30.5 29.9 30 30 30 29 30.9 29

(B) SAND SURFACE (ᵒC)

AIR (ᵒC) TIMES (h) 5m 10m 15m 20m 25m 30m

27 42 06.00 12.00 27.5 42.5 27.5 46 28.9 44 27.5 46 28 49.5 28 49

33 29.5 18.00 00.00 30 28 30 28.5 31 28 30 27.5 29.5 27.5 32 28.5

SEDIMENT COLUMN (ᵒC)

5m 10m 15m 20m 25m 30m

06.00 12.00 30.5 32 31 33 31.5 33 31 35 31 35 31 36

18.00 00.00 31 31 36 31.5 34 32 36 33 36 32 30.5 32

(C) SAND SURFACE (ᵒC)

AIR (ᵒC) TIMES (h) 5m 10m 15m 20m 25m 30m

26 33 06.00 12.00 24 36.5 24.4 40 24 39 25.2 40 24 42 25 39

29 27 18.00 00.00 29 28 28 25 28 25 29.3 24 28 24 27 24

SEDIMENT COLUMN (ᵒC)

5m 10m 15m 20m 25m 30m

06.00 12.00 29 30 30 31.2 31 31.5 31 30 29.1 33 29 34

18.00 00.00 31 29 31 31.1 32 28 32 30.3 33 30 29 32

56

Figure 39: Average air temperatures during the study period

Figure 40: Average temperatures for sand surface of beach zones between times of the day

during June (A), July (B) and August (C)

(A) (B)

(C)

26

27

28

29

30

31

32

33

34

1 2 3

Av

era

ge

ᵒC

Months

Series1 Air

June July August

0

10

20

30

40

50

1 2 3 4

Av

era

ge

ᵒC

Times (h)

Series1 Sand Surface

06.00 12.00 18.00 00.00 0

10

20

30

40

50

1 2 3 4

Av

era

ge

ᵒC

Times (h)

Avera…

06.00 12.00 18.00 00.00

Sand Surface

0

10

20

30

40

50

1 2 3 4

Av

era

ge

ᵒC

Times (h)

Series1 Sand Surface

06.00 12.00 18.00 00.00

57

Figure 41: Average temperature for sediment column of beach zones between times of the day

during June (A), July (B) and August (C)

(A) (B)

(C)

27.5

28

28.5

29

29.5

30

30.5

1 2 3 4

Av

era

ge

ᵒC

Times (h)

Series1

06.00 12.00 18.00 00.00

Sediment Column

29

30

31

32

33

34

35

1 2 3 4

Av

era

ge

ᵒC

Times (h)

Series1

06.00 12.00 18.00 00.00

Sediment Column

28.5

29

29.5

30

30.5

31

31.5

32

1 2 3 4

Av

era

ge

ᵒC

Times (h)

Series1

06.00 12.00 18.00 00.00

Sediment Column

58

Figure 42: Average temperatures of sand surface (A) and sediment column (B) across the beach

zones during the study period

(A)

(B)

26

27

28

29

30

31

32

33

34

35

1 2 3 4 5 6

Av

era

ge

ᵒC

Zones (m)

June

July

August

5 10 15 20 25 30

Months

26

27

28

29

30

31

32

33

34

35

1 2 3 4 5 6

Av

era

ge

ᵒC

Zones (m)

June

July

August

5 10 15 20 25 30

Months

59

6.4. Moisture content of the sand

The moisture content of the sand in each plot, showed a gradient from high moisture content

close to the sea at the 5m zone to slightly lower at the 10m and 15m zones during the study

period (Figures 43, 44). However this pattern did not apply for the zones further away from the

sea (zones of 20m 25m and 30m) as would normally be expected (Figure 43). Measurements of

sand moisture from these zones were only taken from plots 8 and 9, which were the only ones

extending to 20m and 30m respectively. Therefore, the unexpectedly high moisture content

could be a result of errors in the measurements, topographical parameters or other factors.

Due to the above difficulty it was not possible to draw a correlation between moisture content

and burrow densities and sizes. Observations were restricted to the fact that the moisture

content in the plots and periods of highest burrow densities were between 11% and 20.5%

(Figure 23, Appendix 13).

Figure 43: Average counts of moisture content of the sand across the zones of the beach during

the study period

0

5

10

15

20

25

1 2 3 4 5 6

Av

era

ge

Mo

istu

re

Zones (m)

Series1 Sand Moisture

5 10 15 20 25 30

60

Figure 44: Sand moisture content taken from the zones of the beach of each plot during June

(A), July (B) and August (C)

(A)

(B)

(C)

0

20

40

60

80

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Mo

stu

re C

on

ten

t (%

)

Plots

30

25

20

15

10

5

Zones (m)

0

20

40

60

80

100

120

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Mo

istu

re C

on

ten

t (%

)

Plots

30

25

20

15

10

5

Zones (m)

0

20

40

60

80

100

120

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Mo

istu

re C

on

ten

t (%

)

Plots

30

25

20

15

10

5

Zones (m)

61

6.5. Sand granulometry

The beach of the study area consisted primarily of medium sand grain. However some plots

showed coarse grain sand. Granulometric characteristics of the sand are given in Table 6 below.

These results indicate that plots 1, 4, 5, 7, 8, 9, 10, 11, 13 and 14 showed medium grain sand,

while plots 2, 3 and 6 showed coarse grain sand. However, as it can be seen both plots 12 and

15 showed medium grain sand in the first two zones (5m and 10m) and coarse grain sand in the

third zone (15m). Although the majority of plots had medium sand grade, the value of each

plot varied.

Ocypode cursor population was observed in areas with both coarse and medium sand grain. To

test whether grain affects the number of burrows, only the southern site was used, where

disturbance was constant. One possible bias here is that plots 1 and 3 extended only to 5m and

did not include the 6m which was the average distance with highest burrow numbers (as

observed in Figure 32). However, as plot 1 was medium and plot 3 coarse this bias is cancelled.

A Mann Whitney test shows that the difference of the number of burrows between medium

and coarse is not statistically significant (Mann Whitney W=11.5, P=0.8273). Burrow counts

were extremely low in plot 2 and relatively low in plot 3 where the sand was coarse grain.

However, although plot 6 showed coarse sand grain, the burrow density was the greatest along

the study area during the study period (Figure 23, Table 6). The greatest number of burrows

during the study period was counted in plots 4, 5 and 6 (Figure 23) mostly within the zone of

5m but also in the 10m zone (Figure 31) where the grain size ranged from 0.60 to 1.65

(Table 6).

To test if there is any correlation between burrow diameter and grain size only the area inside

was used for the same reason discussed above. Due to the fact that plots did not have the

same area (plots 1 and 3 extended only to 5m and plots 2, 4, 5 and 6 extended to 10m) the

number of burrows in plots 1 and 3 were adjusted by extrapolation to 200m2. Figure 45 below

highlights that there is no significant correlation between burrow diameter and grain size since

the distribution of each size class in coarse and medium sand grain is fairly similar and close to

normal in both cases.

62

Table 6: Granulometry data relating to the sand samples collected from the zones of each plot

of Akrotiri Peninsula. Md = median grain ( )

Zones (m) 5 10 15 20 25 30

Plots Md ( )

1 1.60

2 0 0

3 0

4 1.60 1.65

5 1.50 1.63

6 0.65 0.60

7 1.61 1.65 1.71

8 1.81 1.79 1.60 1.80

9 1.71 1.69 1.15 1.70 1.67 1.60

10 1.40 2.00

11 1.63 1.95

12 1.65 1.64 0.49

13 1.58 1.59

14 1.65 1.55

15 1.51 1.53 0.68

Figure 45: Distribution of each of the six size classes recorded in coarse and medium sand

grain along the southern plots of the study area

-10

-5

0

5

10

15

20

25

30

35

40

45

<10 10 19 20-29 30-39 40-49 >50

Nu

mb

er

of

Bu

rro

ws

Size Classes (mm)

Series1

Series2

Poly. (Series1)

Poly. (Series2)

Sand grain

Coarse Medium

(Coarse) (Medium)

-

63

7. Discussion

7.1. Temporal and spatial distribution, size frequency and burrow density of ghost crab

Although the differences between the three months did not have big statistical significance (as

analyzed in Appendix 8), the abundance peak of number of burrows in the study area was

recorded in July (as shown in Figures 20, 21). Similar results were produced for Ocypode cursor

in north-eastern Mediterranean Turkey by Türeli et.al., (2009) who found that the number of

burrows in July were greater than those in June and August.

During the whole study period the most predominant size classes were those of small (20-

29mm) and medium (30-39mm, 40-49mm) size classes representing 33%, 34% and 19%

respectively (as observed in Figure 26). Only a single burrow diameter less than 10mm was

found (as illustrated in Figure 27) and very few with diameters of 10-19mm (7%) were recorded

during the three-month study period (as shown in Figure 26). Larger crabs with burrow

diameters more than 50mm were also recorded in low densities (7%) throughout the three

months (as observed in Figure 26). The relative absence of larger burrows could to a certain

extent be explained by the suggestion that these are primarily nocturnal and they might plug

their burrow openings during the day (Moss and McPhee, 2006). However this cannot explain

the low numbers of very small burrows, as juveniles who are mostly diurnal and can be seen on

the sand surface near their burrows during the day (Haley, 1969; Hobbs et.al., 2008), have their

burrows open and detectable as noticed in other studies for Ocypode cursor (Türeli et.al., 2009;

Strachan et.al., 1999; Shuchman and Warburg, 1978). Therefore, the low numbers of small

diameter burrows in this study agree more with Milne and Milne (1946) and Barras (1963) who

suggest that juveniles plug their burrows during the daylight and it is difficult to detect. On the

other hand, it could not be ruled out that the counts represent the composition of the local

crab population.

Ocypode cursor (L., 1758) occurs in the supralittoral and upper intertidal zones (Türeli et.al.,

2009), above the watermark but its zone is close to the sea (Strachan et.al., 1999). The present

study highlights that in general the crabs prefer the zones 0-10m for their burrows (as

established in Figures 29, 30, 33, Appendix 9), suggesting that the most preferable distance is

6m from the water line (as detected in Figure 32). Similar to these results are the studies of

Ocypode cursor in northern Cyprus where the most populated area was between 3-12m from

the water edge (Strachan et.al., 1999), in northern Israel where during the summer crabs

concentrated between 5-10m from the sea (Shuchman and Warburg, 1978) and in north-

eastern Mediterranean Turkey where crabs inhabited mainly the area closer to the sea

between 3-7.5m (Türeli et.al., 2009).

A clear, albeit weak, correlation between the size of Ocypode cursor and distance from the sea

was noticed, as the distribution of the crabs across the shore was found to vary with the size of

the crab, with younger ones tending to be closer to the sea and older further away (as

64

demonstrated in Figures 32, 33, 34). Fisher and Tevesz (1979) suggest that the difference in

spatial distribution of adults and juveniles is most possible a function of physiological

competence. In summer small crabs are found only close to the shore and their burrows extend

often to the water level, making their tunnels in the wet sand left by the retreating tide. These

crabs are therefore less terrestrial than adult crabs (Milne and Milne, 1946). Similar

observations have been reported in 2002 from Türeli, et.al., (2009) who mentioned that the

most predominant size classes of burrows occurred within the zones located closer to the sea

were those of 1-1.9cm and 2-2.9cm, while the size classes of burrows occurred within the zones

located further from the sea were those of 2-2.9cm to 3-3.9cm. Shuchman and Warburg

(1978) also noticed that burrow size classes of 1, 2 and 3cm were mostly found in the area

closest to the sea, while burrows with opening diameter of 5cm or more were found more

landwards. Strachan et.al., (1999) found burrows with diameters of less than 10mm and 20-

29mm concentrated in zones closer to the sea, while burrows of 30-39mm and 40-50mm in

zones further away from the sea. A similar relationship between the size of the crab and its

position on the beach was observed for Ocypode cursor at Atlit beach in Israel (Gilad-Shuchman

and Warburg 1977). Juveniles have higher levels of water loss and need to renew their gill

chamber more often than adults (Lucrezi et al., 2009) as these crabs have smaller gill areas

(Chan et.al., 2006), and this could be explain why juveniles were found closer to the sea

(Strachan, et.al., 1999) in a narrow band adjacent to the swash zone (Fisher and Tevesz, 1979)

while adults were found further away (Wolcott, 1976). A further explanation of the location of

juveniles is their higher need of moisture for respiration (Martin, 2006) due to their lower

resistance to desiccation (Turra et.al., 2005; Fisher and Tevesz, 1979), as the water content of

the sand decreases with distance from the sea (Strachan et.al., 1999). Moreover, the length of

the burrow depends on their distance from the sea since burrows of ghost crabs approach the

water table and therefore deeper burrows are found at a greater distance from the sea

(Shuchman and Warburg, 1978) while according to Chan, et.al., (2006) adults are capable to

built deeper burrows than small crabs. On the other hand adults are found further landwards as

they are able to occupy a wider sandy beach moisture gradient than juveniles (Turra et.al.,

2005) because they have bigger gill surface area which helps them to tolerate longer periods

exposed to air alongside with higher resistance to desiccation staying in their burrows during

the day which are more complex and deeper than juveniles (Chan et.al., 2006).

It should also be noted that in this study there was no clear cut distribution of size classes

across the different zones and the area closer to the sea (0-10m) was inhabited from all size

classes as shown in Figures 32, 33, 34. A similar observation has been reported for Ocypode

cursor by Türeli et.al., (2009) and for Ocypode ceratophthalmus by Barras (1963) where larger

ghost crabs also inhibited areas closer to the sea. The distribution of adults across the whole

beach may be related to the food habitats of these crabs which are mostly nocturnal according

to Branco et.al., (2010).

65

7.2. Human disturbance in relation with burrow density

Human disturbance varied significantly between the two sites of the beach (as analysed in

Appendix 10B), since it was obviously lower on the southern site (5%) than the northern (95%)

(as observed in Figure 36). This is due to the fact that the northern site is the popular, open

access area of Lady’s mile beach with high summer recreational activities such as bathing,

picnicking and beach sports. Other human activities were observed during the study period

such as raking of the sand, trampling, car driving on beaches and beach excavation by children

in the upper intertidal zone where the crabs are primarily found, causing disturbance to crab

populations, which is in line with the findings of Turra et.al. (2005). On the other hand the

findings of this study are contrary to the ones for Ocypode cursor in northern Cyprus where the

densest areas of burrows were those frequented by human presence and activities such as

bathing and picnicking showed a positive correlation between burrow numbers and human

presence (Strachan et.al., 1999). The findings of Turra et.al., (2005) show a similar correlation

with the present study, between Ocypode quadrata burrows and human disturbance in Sao

Sebastiao Channel (Grande, Zimbro, Pitangueiras, Gabelo Gordo and Segredo) where burrows

were lower in areas where trampling, beach excavation and sports occurred. Barros (2001) also

noticed this correlation due to the reduction of Ocypode cordimana burrows caused by human

trampling in the three recreational sandy beaches near Sydney in Australia compared to the

other beaches located in two non-urban areas. Furthermore, studies on Ocypode quadrata

have shown that off road vehicles had a detrimental effect on the crabs (Hobbs et.al., 2008;

Steiner and Leatherman, 1981). Off-road vehicles appear to be one of the most important

factors responsible for the decline of ghost crabs on sandy beaches as they can directly crush or

bury the crabs in their burrows especially during the night when they are foraging on the

foreshore, interrupting their reproductive cycle (Lucrezi et.al., 2009) and cause crab desiccation

by modifying the moisture content of the sand (Steiner and Leatherman, 1981) through the

increased compaction (Hobbs et.al., 2008). Another important factor of this decline is the

construction of the upper intertidal zone for commercial or residential use such as roads and

buildings can interfere with the movement of ghost crabs increasing mortality and causing a

significant decline on the crab population (Barros, 2001). A further potential factor for this

decline is human trampling as this can plug the burrows of crabs, causing burrow openings to

collapse and making crabs have lower burrowing and feeding activity (Lucrezi et.al., 2009;

Barros 2001).

Another consideration is that the southern plots, which have much less disturbance than the

northern ones host sea turtle nesting which may be a positive food habitat factor for the crabs

(as discussed in Section 2.2.2.). On the other hand though, the lack of human disturbance and

the turtle nesting attracts foxes in the southern plots and foxes may be preying on crabs. The

picture gets more complicated as the northern plots which are used extensively by people have

more discarded food which may be attracting both crabs and foxes especially during the night.

66

All these factors are related to the food habitat parameter which needs to be taken into

account in further studies.

7.3. Environmental temperatures in relation to burrow density and diameter

It is evident that the sediment column provided the burrows with a thermally stable

environment (28.5-34.4ᵒC) insulating crabs against surface temperature extremes (23.5-46.1ᵒC)

(as observed in Figures 40, 41) which is in line with Chan et.al., (2006). The air temperatures in

this study are above the lower limit of 16ᵒC reported for many Ocypode species by Weinstein

(1998) under which crabs become dormant or migrate inland. However, the air temperatures in

this study extend above the limit of 30ᵒC, for crab activity reported by Lucrezi et.al. (2009).

The temperature patterns of this study agree with the ones for Ocypode cursor in northern

Cyprus where sediment column temperature at 12.00h was lower that both air and sand

surface temperatures (Strachan et.al., 1999).

There was no observed correlation between burrow density and diameter and environmental

temperatures during this study suggesting that the size and density of Ocypode cursor burrows

is related to the distance from the sea (as discussed in Section 7.1.).

7.4. Sand moisture in relation to burrow density and diameter

Due to the reasons explained in Section 6.4, a correlation of moisture content of the sand with

burrow density, in line with Warburg and Shuchman (1979) who found a gradient of moisture

decreasing with distance from the sea together with reduced burrow density, was not possible.

Due to the same reasons a correlation between burrow diameter and sand moisture was not

observed suggesting that the size of Ocypode cursor is related to the distance from the sea (as

discussed in Section 7.1.). On the other hand, the preferred moisture found in this study (11%-

20.5%) is in line with Strachan et.al., (1999) who demonstrated that the water content of the

moist sand near the bottom of crab burrows was about 14%, and Warburg and Shuchman

(1979) who reported preference of Ocypode cursor to moisture alternatives of 15%-20%.

Burrows are mainly serving protection against dehydration, but crabs also require access to

water to moisten their gill chambers (Wolcott, 1976). Ghost crabs are capable of conserving

water and absorbing moisture from damp sand (Warburg and Shuchman, 1979) through

hydrophilic setal tufts located at the base of their legs (Wolcott, 1976; Weinstein, et.al., 1994;

Weinstein, 1998), or on their fourth abdominal segment (Shuchman and Warburg, 1978).

67

7.5. Sand granulometry in relation to burrow density and diameter

The results of this study analysed in Section 6.5 indicate that there is no significant difference

between the number of burrows found in different grain sizes in contrast with Strachan et.al.,

(1999) and Türeli et.al. (2009) who found that ghost crabs are mostly found in areas with

medium sand grain. The findings of this study are more in agreement with Turra et.al., (2005)

where numbers of Ocypode quadrata burrows were high in both medium and coarse sand

grain.

The preferred particle size of Ocypode cursor was found to be between 0.60 - 1.65 Similar

results were previously reported for Ocypode cursor in Northern Cyprus (Strachan et.al., 1999)

where crabs were abundant in areas closer to the sea where the sand grade was between

1.40 - 1.56 .

This study indicates that there is no clear correlation between burrow diameter and grain sizes

of the beach, suggesting that burrow diameter is only related to distance from the sea (as

discussed in Sections 7.1.).

68

7.6. Evaluation of hypotheses in relation to research questions

Hypothesis 1: ‘The highest activity of Ocypode cursor takes place during warm months.’

No significant difference was found between the number of burrows during the three summer

months. The spatial and temporal distribution was successfully established.

Hypothesis 2: ‘Ocypode cursor can benefit from human activities such as discarded food but it

may also be negatively affected by recreational activities.’

A strong negative correlation between crab burrow numbers and human activities was found.

Hypothesis 3: ‘Ocypode cursor highly depends on water. Burrow density decreases away from

the sea.

Burrow densities were found to decrease significantly with distance from the sea.

Hypothesis 4: ‘Sediment temperatures are crucial to the distribution of Ocypode cursor.’

Sediment temperatures were found to be relatively constant providing a thermal insulation to

the extremes of air and sand surface temperatures.

Hypothesis 5: ‘Ocypode cursor highly depends on sand moisture. Juveniles are found closer to

the sea while adults are found further landwards.’

A clear, albeit weak, correlation of burrow size was found with bigger sizes extending further

away from the sea, but no correlation with sand moisture was found.

Hypothesis 6: ‘The densities of Ocypode cursor burrows are higher in medium grain sand.’

This hypothesis was disproved, as burrow numbers did not vary significantly between sand

grain sizes.

69

8. Limitations and Recommendations for future work

The extensive information discovered in this survey is prominent but in order to gain more

knowledge about the spatial distribution of Ocypode cursor and its relationship with human

activities and ecological variables, further research is necessary to carried out as discussed in

Box 2 below.

Box 2: Key limitations of this study and suggestions for future work in this area

Key Limitations and Recommendations for Further work

The study period of the survey was limited to the distribution of Ocypode cursor, since its

dispersal pattern was only investigated during the summer months. Future work should

consider this observation by studying the spatial distribution of Ocypode cursor in both winter

and summer periods which will result in a more comparative data.

The abundance of ghost crabs does not only depend on human activities and on several

ecological variables discovered in this study. Further vital variables (as discussed in Section

2.1.) should be taken into account to obtain an extensive and accurate data relating to the

distribution of Ocypode cursor. A crucial question is whether crabs move away from the sea in

the winter. This will inform management measures to protect their extended habitat

There was a problem with establishing the gradient of sediment moisture content across

along the distance from the sea. More plots extending further back from the sea should be

selected. This will improve the statistical analysis for other parameters as well.

70

9. Conclusions

No significant difference was found between the numbers of burrows during the three months

of the study, although the peak was in July. The predominant sizes during the whole period

were small (20-29mm at 33%) and medium (30-39mm at 34%, 40-49mm at 19%).

The crabs preferred the zones 0-10m for their burrows, the most preferable distance being at

6m from the water line.

A clear, albeit weak, trend was found, where bigger crabs tended to spread further away from

the waterline than smaller ones.

Human disturbance was found to be affecting negatively the abundance of crabs at a high

degree.

The sediment column proved to be providing the burrows with a thermally stable environment

insulating crabs against surface temperature. No correlation was found between burrow

density and diameter and environmental temperatures.

Although due to either the methodology or other errors no consistent moisture content pattern

was found, the preferred moisture was found to be 11-20.5%.

The grain sizes in the study area were found to be medium and coarse and no significant

difference was found between the numbers of burrows in the two sizes.

71

References

Aheto D. W., Asare C., Mensah A. E. and J. Aggrey-Fynn, 2011. Rapid assessment of

anthropogenic impact on exposed sandy beaches in Ghana using Ghost crabs (Ocypode spp.) as

ecological indicators. MEJS, 3(2):93-103.

Akrotiri Environmental Education and Information Centre, (AEEIC) n.d.. Natural Environment.

[ONLINE] Available at:< http://www.english.akrotirienvironment.com/Natural-

Environment.php> (Accessed 16 April, 2013)

Alfonso A. Ramos-Espla, Cebriann D., Demetropoulos A., 2007. Integrated Coastal Area

Management in Cyprus: Biodiversity Concerns on the Coastal Area Management Programme of

Cyprus.UNEP-MAP RAC/SPA: Tunis 69 pp. [ONLINE] [pdf] Available at:<http://www.rac-

spa.org/sites/default/files/doc_pac/pac_chypre.pdf> (Accessed 20 January, 2013)

Barras R., 1963. The burrows of Ocypode ceratophalmus (Pallas) (Crustacea, Ocypodidae) on a

tidal wave beach at Inhaca Island, Mozambique. Journal of Animal Ecology, 32:73-85

Barros, F., 2001. Ghost crab as a tool for rapid assessment of human impacts on exposed

sandy beaches. Biological Conservation 97: 399-404

Carl H. Hobbs, Cynthia B. Landry, and James E. Perry, 2008. Assessing Anthropogenic and

Natural Impacts on Ghost Crabs (Ocypode quadrata) at Cape Hatteras National Seashore, North

Carolina. Journal of Coastal Research, 24 (6):1450-1458

Chan K.K., Chan K.K.Y. and Cheuk M.L., 2006. Burrow architecture of the ghost crab Ocypode

ceratophthalma on a sandy shore in Hong Kong. Hydrobiologia, 560: 43-49.

Charilaou P., A. Perdiou, D. Reynolds, C. Hadjistyllis, T. Hadjikyriakou and M. Colvill, 2012.

Akrotiri Peninsula Environmental Management Plan. [ONLINE] [pdf] Available at:<

http://www.sbaadministration.org/home/docs/eco/20121002_AKI_PEN_MGT_PLAN.pdf>

(Accessed 2 February, 2013)

Chartosia, N., M.-S. Kitsos, TH. Tzomos, E. Mavromati, A. Koukouras, 2010. Diet composition of

five species of crabs (Decapoda, Brachyura) that show a gradual transition from marine to

terrestrial life. Crustaceana, 83(10): 1181-1197

72

Coast radar, n.d. Ladys mile beach information [ONLINE] Available at:<

http://www.coastradar.com/beach-

guide/Europe/Cyprus/Limassol/Lemosos/Ladys%20Mile/1883#.UQ6ckWchbPN> (Accessed 9

February, 2013)

Dahl. E., 1953. Some aspects of the ecology and zonation of the fauna on sandy beaches. Oikos

4(1): 1-27

Dugan J. E., D. M. Hubbard and M. Lastra, 2000. Burrowing abilities and swash behaviour of

three crabs Emerita analoga, Stimpson, Blepharipoda occidentalis Randall, and Lepidopa

californica Efford (Amomura, Hippoidea), of exposed sandy beaches. Journal of Experimental

Marine Biology and Ecology, 255:229-245

Education, 2013. Ocean Regions. [ONLINE] Available at:< http://www.education.com/study-help/article/earthscience-help-ocean-regions/> (Accessed 9 February, 2013) Encyclopedia of the nations, 2013. Cyprus. [ONLINE] Available at:< http://www.nationsencyclopedia.com/economies/Asia-and-the-Pacific/Cyprus.html> (Accessed 2 February, 2013)

Eshky A.A., R. J. A. Atkinson and A. C. Taylor, 1995. Physiological ecology of crabs from Saudi

Arabian mangrove. Marine Ecology progress series, 126:83-95

European Environmental Agency (EEA), 2010. Nature protection and biodiversity (Cyprus) [ONLINE] Available at:< http://www.eea.europa.eu/soer/countries/cy/soertopic_view?topic=biodiversity> (Accessed 3 February, 2013) Ewa-Oboho, I.O., 1993. Substratum preference of the tropical estuarine crabs, Uca tangeri

Eydoux (Ocypodidae) and Ocypode cursor Linne (Ocypodidae). Hydrobiologia, 271:119-127.

Fisher, J.B. and M.J.S. Tevesz, 1979. Within-habitat spatial patterns of Ocypode quadrata

(fabricus) (Decapoda, Brachyura) . Crustaceana (supplement) 5:31-36

Gifford A. Charles, 1962. Some Observations on the General Biology of the Land Crab,

Cardisoma guanhumi (Latreille), in South Florida. Biological Bulletin, 123(1):207-223

Gilad-Shuchman, E. and M.R. Warburg 1977. The dispersal of the sand-crab Ocypode cursor and

its behavior towards moisture and temperature gradients. Israel Journal of Zoology., 26: 264-

265

73

Google maps, 2013 [ONLINE] Available at:< http://maps.google.co.uk/> (Accessed at 1 February 2013) Griffin, D. J., 1971. The ecological distribution of Grapsid and Ocypodid shore crabs (Crustacea:

Brachyura) in Tasmania. Journal of Animal Ecology, 40:597-621

Haley, S. R., 1969. Relative growth and sexual maturity of the Texas ghost crab, Ocypode

quadrata (Fabricius) (Brachyura Ocypodidae). Crustaceana 17: 285-297

Hughes, D.A., 1966. Behavioural and ecological investigations of the crab Ocypode

ceratophthalmus (Crustacea: Ocypodidae). Journal of Zoology., Lond., 150:129-143

Horch, K., 1975. The acoustic behaviour of the Ghost crab Ocypode cordimana Latreille, 1818

(Decapoda, Brachyura). Crustaceana 29 (2):193-205

IUCN, 2012. Cyprus. [ONLINE] Available at:< http://iucn.org/about/union/secretariat/offices/europe/resources/country_focus/cyprus/> (Accessed at 9 February, 2013) Jones, D.A. 1972. Aspects of the ecology and behaviour of Ocypode ceratophthalmus (Pallas)

and O. Kuhili de Haan (Crustacea: Ocypodidae) Journal of Experimental Maine Biology and

Ecology 8: 31-43

Joaquim O. Branco, Juliano C. Hillesheim, Helio A. A. Fracasso, Martin L. Christoffersen amd

Cristiano L. Evangelistra, 2010. Bioecology of the Ghost crab Ocypode quadrata (Fabricius,

1787) (Crustacea: Brachyura) compared with other intertidal crabs in the Southwestern

Atlantic. Journal of Shellfish Research, 29(2):503-512

Leonardo, da Rosa C. and Carlos A. Borzone, 2008. Spatial distribution of the Ocypode quadrata

(Crustacea: Ocypodidae) along estuarine environments in the Paranagua Bay Complex,

southern Brazil. Revista Brasileira de Zoologia 25(3): 383-388

Lisa Izzo and Nikhita Kothari, 2011. "Ocypode quadrata" - Animal Diversity Web. [ONLINE]

Available at: <

<http://animaldiversity.ummz.umich.edu/accounts/Ocypode_quadrata/#4A459D1A-767D-

445A-BBD6-4BF8E5D419B6> (Accessed 9 February, 2013)

74

Lucrezi, S., Schlacher, T.A. and Walker, S., 2009. Monitoring human impacts on sandy shore

ecosystems: a test of ghost crabs (Ocypode spp.) as biological indicators on an urban beach.

Environmental Monitoring and Assessment, 152:413-424.

Magalhaes W.F., Lima J.B., Barros F., Dominguez J. M. L., 2009. Is Ocypode quadrata (Fabricius, 1787) a useful tool for exposed sandy beaches management in Bahia State (Northeastern Brazil)? Brazilian journal of oceanography 57(2): 149-152

Martin, A.J., 2006. Resting traces of Ocypode quadrata associated with hydration and

respiration: Sapelo Island, Georgia, USA. Ichnos 13:57-63

McMahon, B.R. & Burggren, W.W., 1988. Respiration. In W. W. Burggren & B. R. McMahon, eds.

Biology of the land crabs. Melbourne, Australia: Cambridge University Press, pp. 249-297.

Milne, L.J. and M.J. Milne, 1946. Notes on the behavior of the ghost crab. American Naturalist

80:362-380

Mitchell, 2007. Ghost crabs: Hungry nocturnal ghosties [ONLINE] Available at:<

http://www.mitchellspublications.com/guides/shells/articles/0057/> (Accessed 9 February,

2013)

Moss D., McPhee D.P., 2006. The impacts of recreational four-wheel driving on the abundance

of the ghost crab (Ocypode cordimanus) on subtropical beaches in SE Queensland. Coastal

Management, 34: 133–14

NASA Earth Observatory, 2001. Cyprus. [ONLINE] Available at:< http://earthobservatory.nasa.gov/IOTD/view.php?id=1343> (Accessed 2 February, 2013) Papari, M., 2009. Climate change impacts on coastal and marine habitats of Cyprus. [ONLINE] [pdf] Available at: < http://cyprus-institute.us/2009/Parari-M_Climate_Change.pdf> (Accessed 1 February, 2013) Pavement Interactive, 2011.Gradation test. [ONLINE] Available at:< http://www.pavementinteractive.org/article/gradation-test/> (Accessed 22 January, 2013) Pfannkuch H.O. and Rick Paulson, n.d. Grain size distribution and hydraulic properties. [ONLINE] Available at:< http://faculty.njcu.edu/wmontgomery/Coastal_Zone/Grain%20Size%20Distribution.htm> (Accessed 23 January, 2013)

75

Quijon, P.E. Jaramillo and H. Contreras, 2001. Distribution and habitat structure of Ocypode

guadichaudii. H. Milne Edwards and Lucas, 1843, in Sandy beaches of Northern Chile.

Crustaceana, 74 (1): 91-103

Robert L. Folk and William C. Ward, 1957. Brazos river bar: A study in the significance of grain

size parameters. Journal of Sedimentary Petrology, 27(1): 3-26

Salmon Michael, 1983. Acoustic ‘calling’ by fiddler and Ghost crabs. [ONLINE] Available at:<

http://australianmuseum.net.au/Uploads/Journals/17629/372.pdf> (Accessed 2 February,

2013)

Sassa, S. And Y. Watabe, 2008. Threshold, optimum and critical geoenvironmental conditions

for burrowing activity of sand bubbler crab, Scopimera globosa. Marine Ecology Progress Series,

354: 191-199

Schuchman, E. & Warburg, M.R., 1978. Dispersal, population structure and burrow shape of

Ocypode cursor. Marine Biology, 49:255-263

Serpent, 2013. Classification: Order Decapoda (Crabs, lobsters, prawns, shrimps). [ONLINE]

Available at:< http://archive.serpentproject.com/view/classification/order_2.html> (Accessed

1 April, 2013)

Seth L. Button, 2010. Resource stress and subsistence practice in early prehistoric Cyprus. [ONLINE] Available at:< http://deepblue.lib.umich.edu/bitstream/handle/2027.42/75840/sbutton_1.pdf;jsessionid=8D7CB14954C81E39F25D571995AFBF88?sequence=1> (Accessed 3 February, 2013) Specht J., 1985. Crabs as disturbance factors in tropical archaeological sites. Australian

archaeology, 21: 11-18

Steiner A.J. and S. P. Leatherman, 1981. Recreational impacts on the distribution of Ghost crabs

Ocypode quadrata Fab. Biological Conservation 20: 111-122

Strachan, P.H., R.C. Smith, D.A.B. Hamilton, A.C. Taylor and R.J.A. Atkinson, 1999. Studies on the

ecology and behaviour of the ghost crab, Ocypode cursor (L.), in Northern Cyprus. Scientia.

Marina., 63(1): 51-60.

Türeli, C., O. Duysak, E. Akamca, V. Kiyagi, 2009. Spatial distribution and activity pattern of the

ghost crab, Ocypode cursor (L., 1758) in Yumurtalik Bay, North-Eastern Mediterranean Turkey.

Journal of Animal and Veterinary Advances, 8(1): 165-171.

76

Turra, A., M.A.O. Goncalves and M.R. Denadai, 2005. Spatial distribution of the ghost crab

Ocypode quadrata in low-energy tide-dominated sandy beaches. Journal of Natural History 39

(23): 2163-2177

Valero-Pacheco, E., F. Alvarez, L.G. Abarca-Arenas and M. Escobar, 2007. Population density

and activity pattern of ghost crab Ocypode quadrata in Veracruz , Mexico. Crustaceana 80 (3):

313-325

Vannini M., 1980a. Researches on the coast of Somalia. The shore and the dune of Sar Uanle.

27. Burrows and digging behaviour in Ocypode and other crabs (Crustacea Brachyura). Monitore

zoologico italiano., (N.S.) 13:11-44

Vannini, M. 1980b. Notes on the behavior of Ocypode ryderi Kingsley (Crustacea, Brachyura).

Marine Behaviour and Physiology, 7: 171-183

Warburg, M.R. and E. Shuchman 1979. Experimental studies on burrowing Ocypode cursor (L.)

(Crustacea: Ocypodidae), in response to sand moisture. Marine Behaviour and Physiology

6:147-156

Weinstein, R.B., Full, R.J. and Ahn, A.N., 1994. Moderate dehydration decreases locomotor

performance of the ghost crab, Ocypode quadrata. Physiological Zoology, 67(4):873-891.

Weinstein, R.B., 1995. Locomotor behaviour of nocturnal Ghost crabs on the beach: Focal

animal sampling and instantaneous velocity from three-dimensional motion analysis. Journal of

Experimental Biology, 198:989-999

Weinstein, R.B. 1998. Effects of temperature and water loss on terrestrial locomotor

performance in land crabs: integrating laboratory and field studies. American Zoologist 38: 518-

527

Wolcott, T. G., 1976. Uptake of soil capillary water by ghost crabs. Nature, 264: 756-757.

Wolcott, T.G. 1978. Ecological role of ghost crabs, Ocypode quadrata (Fabricius) on an ocean

beach: Scavengers or predators? Journal of Experimental Marine Biology and Ecology 31:67-82

77

Appendices

1: Description of human activities alongside with their scale (A) and human disturbance scale alongside

with their description (B)

(A)

(B)

Disturbance

Scale Description

Trampling (people, dog, fox) 1 If trampling of people and/or dog and/or fox is abundant in the plot, or on the area of about 20m around the plot

Human presence 1 2

If people are <20 in the plot, or on the area of about 20m around the plot If people are >21 in the plot, or on the area of about 20m around the plot

Human activities (cafes/restaurants, discarded food/litter, excavation, off-road vehicles, sand ranking, beach games/sports)

1 2

If cafes/restaurants and/or discarded food/litter are present in the plot, or on the area of about 20m around the plot If excavation and/or off-road vehicles, sand ranking, and/or beach games/sports are present in the plot or on the area of about 20m around the plot

Disturbance scale Description

0 None of the above activities

1 One (of scale 1) of the above activities

2 Two (of scale 1), or one (of scale 2) of the above activities

3 Three (of scale 1), or one (of scale 1) and one (of scale 2) of the above activities

4 Two (of scale 1) and one (of scale 2), or two (of scale 2) of the above activities

5 Three (of scale 1) and on (of scale 2) or two (of scale 2) and one (of scale 1) of the above

activities

78

2: Zones of the beach in plot 4 (zones of 5m and 10m) where samples of sand moisture, sand

temperatures, sediment column and sand granulometry were taken

3: Sample analysis data of sand sample taken from the zone of 20m of the plot 8

Total = 55.5 g Total = 99.98 %

No. of sieve Weight of size fraction (g)

Weight percent (%)

Cumulative weight retained (%)

Cumulative weight passed (%)

250 0.7 1.26 99.98 0.02

120 0.5 0.9 98.72 1.28

100 8 14.41 97.82 2.18

80 9 16.21 83.41 16.59

60 33.5 60.36 67.2 32.8

40 1.4 2.52 6.84 93.16

30 1.7 3.06 4.32 95.68

20 0.7 1.26 1.26 98.74

79

4: Grain size classification table

U. S. Standard Sieve Mesh

Millimeters (fractional)

Millimeters Microns Wentworth Size Class

(1 Kilometer) -20

Use 4096 -12

1024 -10 Boulder (-8 to -12φ)

wire 256 -8 Cobble (-5 to -8φ)

64 -6

squares 16 -4 Pebble (-2 to -5φ)

5 4 -2

6 3.36 -1.75

7 2.83 -1.5 Granule (-1 to -2φ)

8 2.38 -1.25

10 2 -1

12 1.68 -0.75

14 1.41 -0.5 Very coarse sand (0 to -1φ)

16 1.19 -0.25

18 1 0

20 0.84 0.25

25 0.71 0. 5 Coarse sand (1 to 0φ)

30 0.59 0.75

35 1/2 0.5 500 1

40 0.42 420 1.25

45 0.35 350 1.5 Medium sand (2 to 1φ)

50 0.3 300 1.75

60 1/4 0.25 250 2

70 0.21 210 2.25

80 0.177 177 2.5 Fine sand (3 to 2φ)

100 0.149 149 2.75

120 1/8 0.125 125 3

140 0.105 105 3.25

170 0.088 88 3.5 Very fine sand (4 to 3φ)

200 0.074 74 3.75

230 1/16 0.0625 62.5 4

270 0.053 53 4.25

325 0.044 44 4.5 Coarse silt (5 to 4φ)

Analyzed 0.037 37 4.75

1/32 0.031 31 5

by 1/64 0.0156 15.6 6 Medium silt (6 to 5φ)

1/128 0.0078 7.8 7 Fine silt (7 to 6φ)

Pipette 1/256 0.0039 3.9 8 Very fine silt (8 to 7φ)

0.002 2 9

or 0.00098 0.98 10 Clay

0.00049 0.49 11 (Some use 2μ or 9φ

Hydrometer 0.00024 0.24 12 as the clay boundary)

0.00012 0.12 13 (Pfannkuch and Paulson, n.d.)

80

5: Weekly recordings of Ocypode cursor burrows along the study area during each month

Week1 Week 2 Week 3 Week 4

Plots June July August June July August June July August June July August

1 0 2 0 0 0 1 0 0 0 2 0 0 2 1 0 0 0 0 0 0 0 0 0 0 0 3 1 0 1 0 0 0 0 1 1 0 1 0 4 0 6 8 3 6 10 4 5 4 3 4 4 5 4 4 6 5 5 5 6 4 3 2 7 3 6 3 4 6 9 7 4 8 4 4 1 6 4 7 6 1 0 1 1 0 4 1 0 0 0 0 8 1 0 2 0 1 1 2 0 0 0 0 0 9 3 3 2 1 4 1 0 8 7 0 3 1 10 1 0 0 1 0 0 0 0 0 1 0 0 11 2 0 0 0 0 0 0 1 0 0 0 0 12 0 1 0 2 0 0 0 2 0 0 2 0 13 3 1 0 2 0 0 1 0 0 0 0 0 14 0 1 1 0 0 0 0 1 1 0 0 0 15 0 2 1 2 2 1 3 1 2 1 1 1 TOTAL 25 25 27 26 26 23 28 28 22 10 24 13

6: Adjusted weekly recording of Ocypode cursor burrows along the study area during each

month

Week1 Week 2 Week 3 Week 4

Plots June July August June July August June July August June July August

1 0 12 0 0 0 6 0 0 0 12 0 0 2 3 0 0 0 0 0 0 0 0 0 0 0 3 6 0 6 0 0 0 0 6 6 0 6 0 4 0 18 24 9 18 30 12 15 12 9 12 12 5 12 12 18 15 15 15 18 12 9 6 21 9 6 9 12 18 27 21 12 24 12 12 3 18 12 7 12 2 0 2 2 0 8 2 0 0 0 0 8 1.5 0 3 0 1.5 1.5 3 0 0 0 0 0 9 3 3 2 1 4 1 0 8 7 0 3 1 10 3 0 0 3 0 0 0 0 0 3 0 0 11 6 0 0 0 0 0 0 3 0 0 0 0 12 0 2 0 4 0 0 0 4 0 0 4 0 13 9 3 0 6 0 0 3 0 0 0 0 0 14 0 3 3 0 0 0 0 3 3 0 0 0 15 0 4 2 4 4 2 6 2 4 2 2 2 TOTAL 64.5 71 76 71 65.5 67.5 74 67 53 35 66 36

81

7: Average number of burrow found in 5m, 10m and 15m in plots 7, 8, 9, 12 and 15 during the

study period

Months Plots 5m 10m 15m June 7 2 18 2

8 0 0 3

9 0 1 1

12 2 2 0

15 2 6 4

July 7 2 4 0

8 1.5 0 0

9 2 1 1

12 3 8 2

15 10 2 0

August 7 0 0 0

8 4.5 0 0

9 0 1 3

12 0 0 0

15 2 8 0

Average no. of Burrows 2.07 3.40 1.07

8: ANOVA results for differences in the number of burrows between the different periods of the

summer

82

9: Two-Sample T-Test for the differences in the number of burrows between (A) 0-5 and 10-

15m and (B) 5-10 and 10-15m during the study period

(A)

(B)

10: Mann Whitney test results for differences in the number of burrows between the two sites

(A), human disturbance between the two sites of the study area (B) and differences in the

number of burrows between plots in the southern site with coarse and medium sand grain (C)

(A) (B)

83

(C)

11: Pearson’s Correlation between the number of burrows and human disturbance along the

study area during the study period

12: Kruskal-Wallis test for the difference in the average human disturbance between the

different study periods

84

13: Data results of and moisture samples (200g) taken from depth of 25cm along the plots of

the study area in June, July and August

85