Nesting Ridleys Need Critical Protection and Its High Nest Successes at Devi Coast Odisha

OPEN JOURNAL OF OCEAN AND COASTAL SCIENCESVolume 1, Number 1, October 2014

OPEN JOURNAL OF OCEAN AND COASTAL SCIENCES

Nesting Ridleys Need Critical Protectionand Its High Nest Successes at Devi CoastOdishaBehera S. K. 1*, Kar C. S.2, K. Sivakumar3 and Choudhury B. C.31 Integrated Coastal Zone Management Unit Berhampur, Odisha, India.2 Department of Forest and Environment, Bhubaneswar, Odisha, India.3 Wildlife Institute of India, Chandrabani, #18 Dehradun, Uttrakhanda, India.

*Corresponding author: [email protected]

Abstract:Olive Ridleys sea turtle are known to nests both enmass and solitary in the south sand spit ofRiver Devi, Odisha. After 1999 enmass nesting, only solitary activity is observed in this partof beach. This study was done to evaluate the nesting activity along Devi coast for period offour years, 2006-10 and hatchling successes of Olive Ridley solitary nests in one of the islandwhere no human habitation is present was carried out from December 2008 to May 2010, intotal 7642 numbers of nests was recorded within four years of which 5058 nest were from themain land beach and rest 2584 from island beach. A total of 309, nests were marked witha pole and monitored for hatchling successes. It was calculated, 94% of eggs were hatchedsuccessfully, and 91% of hatchling emerged out successfully. This study shows that nest locatedbetween 20 to 40 m distances from the high tide mark were more successful than the nest inother part of the beach. There was not much difference in the hatchling successes between thethree periods of nesting (nesting, peak nesting, post nesting) and within years. Since high levelnesting activity and high hatchling successes of nests were observed, Devi rookery still to be apotential mass nesting ground provided near off-shore fishing is managed properly especiallyduring peak breeding period between February and April. Intensive near off-shore fishing areassumed to be reason for non-occurrence of mass nesting in the Devi rookery. Higher numberof stranded turtles coincides with the peak nesting time during the study period.

Keywords:Olive Ridley; Nest Density; Devi; Hatchling Successes; Mortality

1. INTRODUCTION

The olive ridley turtle (Lepidochelys olivacea) generally opt to lay the eggs on beaches with highhumidity levels. Most of these are found near large and small river mouths or estuaries [1, 2]. Similarly,solitary nesting activity is found all along the coast of Odisha during the nesting season i.e. Decemberto May. This study confirms that the nesting activity is throughout year like Gahirmatha [3] and onlyfew instances mass nesting has being recorded yet after the discovery of this nesting beach in (1981 Kar)when mass nesting took place, but there is no record of estimation. After a gap of five year another mass

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nesting took place in 1984-85. During the year 1996-97 [4] 3rd mass nesting took place and the last massnesting was recorded during 1998-99 [4] after that there is no record of mass nesting till date. Apart fromthis solitary nesting activity occurs throughout the year. Solitary nesting activity reaches its peak betweenFebruary to April; the nesting phenomenon gradually decreases in coming months. Although most nestare predated or destroyed by jackals, stray dogs in the main land beach but nests in one of the island, fromwhere the mass nesting have being reported is total predator free and almost all the nest are naturallyhatched and hatching goes to sea after hatching.

Solitary nesting, mortality is higher during the breeding period in comparisons to any other beachesalong the Odisha coast [? ]. Mortality of the turtles is due to intense fishing activity in near shore waterduring the breeding season [? ]. Most of the mortality results due to high near shore fishing in this regionduring the nesting and peak nesting period, January to February [? ] and in subsequent months. This wasan attempt to study the pattern of mortality and nesting which is induced by intense near shore fishingactivity at Devi rookery.

There are many studies on the hatchling successes of two rookeries along the east coast of Odisha,these studies are restricted to the mass nesting beaches and done during the mass nesting period [3–7]. Nosuch studies had yet been done on the hatchling successes rate of the solitary nesting activity along theeast coast of Odisha. This study will put light on the hatchling successes rate of turtles at Devi rookeryand the activity of fishing affecting the nesting of turtles.

2. STUDY AREA

This nesting beach is located between the border of Jagatsinghpur and Puri District of Odisha. Devicoast is stretched on the either side of river Devi (N 19◦ 57’ 36.0” E 86◦ 23’ 05.5”), towards north it isstretched up to Petaphutai river mouth (N 20◦ 37’0.60” E 86◦ 25’59.41”) and up to Kadua river mouthtowards south (N 19◦ 54’ 31.4” E 86◦ 14’ 24.0”) total stretch is 32 km. the total stretch is planted withcasurina forest near to the shore line. Toward northeast of Devi mouth a island is present which is devoidof vegetation It has a sandy beach of about 1.5 km in length; the beach is approximately 150 m Wide fromthe high tide line to the other side of the island and has a soft slope. In this remote Island we observednesting of Lepidochelys olivacea from December 2006 to May 2010.

3. Result and Discussion

3.1 Main land (Kadua Mouth to Devi Mouth)

During the study period (2006 to 2010) there was no arribada nesting. However, the high solitarynesting was observed at Devi rookeries during the study period (Figure 1) where more than 100 turtlesnested in single night on this beach. During 2010 more than 500 turtles nested in a single night and thisevent lasted for two days in the island of Devi rookery. This event is an indication towards the potentialityof the enmass nesting. But the exact reason why mass nesting fails during certain year is not knownbut they may be influenced by the surrounding environment including anthropogenic disturbances andchanges in beach geomorphology of the nesting area.

Beach monitoring was done from throughout year, for encountering nesting activities. The main nestingactivity starts from December every year and reaches its peak during the month of February and Marchevery year. The highest nests were recorded within February to March during 2006-07 (240), 2008-09(682) and 2009-10 (739). Late nesting was observed during 2007-08 which take place during the month

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Nesting Ridleys Need Critical Protection and Its High Nest Successes at Devi Coast Odisha

Map showing the mass nesting island (Robert Island) and the main land from Devi to Kadua mouth.

Table 1. Nest and nest density per day of olive ridley turtles in main land (kadua to Devi river mouth) monthly basisduring 2006 to 2010 at Devi rookery.

Year 2006-07 2007-08 2008-09 2009-10N Nd N Nd N Nd N Nd

June - - - - 2 2 1 1

July - - 1 1 1 1 - -

August - - 1 1 - 1 1

September - - - 2 2 2 2

October - - 1 1 2 2 5 1.6

November - - 1 1 1 1 1 1

December - - 1 1 4 2.00 41 4.56

January 21 1.91 5 1.67 53 5.89 92 8.36

February 44 2.93 94 3.92 682 40.12 739 49.27

March 240 10.91 354 15.39 628 25.12 677 32.24

April 209 11.00 481 22.90 275 13.10 328 25.23

May - - - - 27 4.50 41 3.73N= Number of nest; Nd= Nest density/day

of April.One way ANOVA was carried out on the nesting density of the turtles between the years for each years,

showed significant variation between the seasons (F = 1.109, df = 3 P < 0.36). We conclude that therewas statistically significant difference in the mean of turtle nesting density within the years in all fouryears of study period.

During the four years (2006-07; 2007-08; 2008-09 & 2009-10) of study period we observed 67, 76, 89,88 days where there was nesting crawls and in remaining nights there were no nesting or false nestingcrawls by turtles respectively. The highest nesting activities were recorded during March (22, 23, 25,21 days out of 31 days for each respective year). However, in terms of nesting aggregation, maximumnumbers of turtles were encountered on the beach during April 2006-07 and 2007-08 whereas in 2008-09and 2009-10 it was highest in February (Table 1). Maximum numbers of nests were recorded between20-30 m from HTL and 70- 80 m from the vegetation line (Figure 2 & Figure 3).

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Figure 1. Nesting recorded during 2006 to 2010 nesting season (December – May) at Devi rookery.

Figure 2. Distance of olive ridley nests from the high tide line at Devi rookery during 2006-10.

Figure 3. Distance of olive ridley nests from the vegetation line at Devi rookery during 2006-10.

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Table 2. Nesting at new Akashdhia Island of Devi rookery.

Year 2006-07 2007-08 2008-09 2009-10Month N Nd N Nd N Nd N NdOctober - - - - 2 2 3 1.5

November - - - - 5 1.6 7 1.75

December - - - - 37 6.16 42 10.5

January - - - - 39 13.00 41 13.66

February 21 3.00 16 4.00 57 14.24 138 23.00

March 35 5.83 49 9.8 49 7 1811 164.63

April 58 14.5 53 17.66 53 8.83 29 7.25

May - - - - 23 3.83 16 2.66N= Number of nest; Nd= Nest density/day

3.2 Solitary Nesting at Island (Akashdhia)

Beach monitoring was done from October to May during all four years for encountering nestingactivities. Of these in 17, 12, 37, 40 days there was nesting crawl and in remaining nights there were nonesting or false nesting crawls by turtles. The highest nesting activities were recorded during March 6, 5,7, 11days out of 31 days for each respective year). However, in terms of nesting aggregation, maximumnumbers of turtles were encountered on the beach during April 2006-07 and 2007-08 whereas in 2008-09it was highest in February and during March in 2009-10 (Table 2).

3.3 In situ observations

During the four year of study period 2006-10 we could perform the hatchling successes for two year(2008-09 & 2009-10) as the island was totally free from predator. During first two years 2006-08, islandgeomorphology was slightly different as island got connected with the main land through a submergedsand bar during low tide and the most of nests were predated by jackals, hyena, and dogs. DuringDecember 2008 to May 2010 we made nightly patrols at island Beach of Devi rookery (from 7 p.m. to7 a.m.), to locate nesting females or nests. The entire nests were natural hatched and none of the turtleeggs were excavated and transferred to hatchery. In order to monitor the number of nests and time ofdevelopment, we marked every nest, after complete nesting of turtle with a stake on which the date anda serial number were recorded. Distance between the nest and the high tide line was obtained with ameasuring tape (±1 cm).

We closely monitored the nests persistently between 45 and 70 days after oviposition. To determinenest success (hatchling successes & emergence successes) for each nest on the island, we counted thenumber of dead hatchlings, early embryonic death, late embryonic death and unfertilized eggs (unhatchedeggs having any mark of embryonic development or not). Percent of emergence success was calculatedfor each nest [8]. Hatchling success was considered the percentage hatchlings that emerged from the eggslaid and the percent of dead hatchlings [9].

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Figure 4. Incubation period of the solitary nest at Devi Island from December 2008 and May 2010.

3.4 Calculation as per (Harry et.al, 2011)

Hatching Success =No. o f hatching emerged f rom nest + No. o f dead embryo

Clutch size o f nest×100

Emergin Success =No. o f hatching emerged f rom nest

Clutch size o f nest×100

3.5 Density of nests

Study was carried out in island where mass was recorded, a total of 309 nests, 59 & 250 in eachrespective year and the average density of nest during the nesting period from December to May was22.08 nest\km, 173.9 nest\km in the respective years 2008-09, 2009-10.

3.6 Incubation Period & clutch size

Over all the incubation period for 309 nests during 2008 to 2010 was 50.8 ± 3.7 days. For the year2008-09 it was 48.8 ± 1.9 and 2009-10, 51.3 ± 3.8 days. The overall clutch size of turtle nest were 138.5± 18.9 (range = 62 to 173, n = 309). On further classification of a nesting season within a year accordingto the total frequency of nesting activity, we divided into three periods, nesting (December-January), peaknesting (February- March) and post nesting (April-May). The average size of clutch was 133.04 ± 11.4,146.3 ± 12.7 and 142.2 ± 17.2 respectively to the periods. The clutch size was highest during the nestingperiod and gradually decreased towards the post nesting periods. Similarly the average of incubation daysgradually decreased, which were 59.6 ± 2.4, 52.1 ± 2.1, 50.4 ± 1.7 days (Figure 4) respectively to threeperiods. The least was found for post nesting period.

3.7 Nest successes

The overall hatching success of turtle eggs at Devi during 2008 to 2010 was 94.03 ± 4.4 (range = 46 to173 n = 309 nests). The hatchling success for the year 2008-09, 2009-10 was 89.28 ± 7.2 & 95.2 ± 2.3

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Figure 5. Fate of eggs inside the nest during 2008-2010 at Devi rookery.

respectively. We have done univarient ANOVA for the hatchling success between the years which showsthere is no significant difference in the nest (F = 0.087 df = 1; p < 0.769) and the hatchling successeshave same variance. The overall percent of dead embryo was 2.72 ± 1.6 and percent of unfertilized eggsper nest were 2.49 ± 1.8 (Figure 5)

Compared to the Gahirmatha rookery the emergence success of the turtle hatchlings at Devi was alsoconsiderably higher (WII, 2011). The overall emergence success during 2008 to 2010 was 91.3 ± 5.2(range = 46 to 173 n = 309nests). The embryonic mortality was only 2.6% In comparison to Gahirmatha[3, 4], the incubation success at Devi is extremely high as Devi beach receives highly solitary nest whichis less dense than Gahirmatha. Although Devi receives smaller number of nesting turtles in comparison toGahirmatha, it’s potential in terms of a stable and more productive beach.

The mean hatching success rate and the emergences successes rate varies from 83.8 to 97.01 and69.78 to 96.1 at Rushikulaya [4] in another study [7] hatchling successes was 89.64. Whereas at Devithe hatching successes rate is 89.28 to 95.27 and the rate of emergences is 86.54 to 92.45. The lessdifference in the hatching successes rate and the emergences successes in the consecutive years as studiedby [4] make the solitary nesting beaches more important than the mass nesting beaches in concern to theproductivity.

3.8 Nest successes

We grouped the nesting in three periods according to the frequency of nesting; nesting, peak nestingand post nesting. In total 309 nests were excavated in two years 24 during nesting, 210 in peak nesting,75 in post nesting period to determine the rate of hatching successes between the periods. Although therewas not much difference in the hatchling and emergence success and it was highest during the post nestingperiod 95.54 ± 2.3 & lowest during nesting period 94.36 ± 1.8 (Figure 6). Similarly the percentage ofemergence successes was higher during the post nesting period and lowest during nesting season 92.8 ±2.8 & 91.7 ± 2.2 (Figure 6). Univarient ANOVA demonstrated that there is no significant variation in theperiods of hatchling success (F= 0.656, df =2, P<0.580)

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Figure 6. Hatchling success and emergence success during pre-nesting, nesting and peak nesting period at devirookery 2008-10.

Figure 7. Figure showing the comparison of Mortality and nesting during the study period at Devi rookery, Odisha

3.9 Nest in relation to high tide line

We grouped these nest sites into seven intervals according to their closeness to the tide line and thenobserved for any differences between them regarding hatch success, there was significant variation (F= 0.737; d f = 5; P < 0.05) We observed that the highest nest success was found in the nests locatedbetween 20 and 30 m above the tide line, followed by that at the nest sites between 30 and 40 m. Nestsites found <20 m and those >40 m were grouped and these sites nest success was low (Table 3).

3.10 Discussion

Near shore trawling is the major concern, fishing season starts with the nesting season of turtlesat Odisha coast. The density of fishing activity found in the near offshore water is more where thecongregation is found basically within 5km from the coast line. Majority of near shore fishing activityis directly related to the mortality of turtles as it shows sudden hike in the mortality figure. During the

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Table 3. number of nest differing from high tide line and its nest successes.

DistanceFrom HTL

in m

No. OfNest

No. ofhatchlingemerged

No. ofdead

hatching

Undevelopedhatchlings

(early)

Undevelopedhatchlings

(late)

Unfertilizedeggs

Clutchsize

Emergencesuccesses

(%)

Hatchlingsuccesses

(%)10 -20 17 2276 65 60 51 52 2504 90.9 93.5

20-30 120 15424 372 227 272 388 16683 92.5 94.7

30-40 104 13196 410 166 208 357 14337 92.0 94.9

40-50 46 5818 196 117 116 144 6391 91.0 94.1

50-60 19 2253 73 78 78 66 2548 88.4 91.3

60-70 3 247 56 45 61 46 455 54.3 66.6

peak nesting period highest mortality was also found due to increase in the density of near shore fishingactivity (Figure 6). That is from February to April. As due to higher mortality we could not relate thearribada nesting but this type of near shore trawling activity must have its effect in long period of time.

The clutch size also varied according to season the highest numbers of eggs were laid during theinitiation of nesting period followed by peak nesting period and the lowest during nesting / post nestingperiod. The incubation periods were related and the elapsed times were similar in October, November andDecember (55-60days), January and February (50-55 days) but were lowered in March and April (45–50 days), the month with the higher temperature have the lower incubation period. There was not muchdifference in the hatchling and emergences successes rate within the period.

Nest success (hatchling and emergences successes) is strongly affected by site selection and thesite’s physical characteristics [8]. These same factors also influence the level of activity and speed ofdisplacement of hatchlings from the nest to the sea [10, 11] which decreased considerably at distancesfurther away from the tide line. With regards to the distance intervals analyzed, the highest nest successwas found between 20 and 40 m above the tide line; this suggests that the optimum conditions of humidityand temperature are found The lowest nest success in the two extreme intervals is due to the fact that, at< 20 m, nests are exposed to wave action and humidity is too high to allow good embryonic development.On the other hand, at >40 m, humidity is much lower and temperature is higher, which also negativelyaffects development of hatchlings which is similar to [12].

ACKNOWLEDGMENTS

We are thankful to PCCF(WL)& CWW, Odisha, for providing support during the study period. We arealso grateful to the Director Wildlife Institute of India, Dehradun, for providing technical and logisticalsupport during the fieldwork. We are thankfully acknowledging the Directorate General of Hydrocarbon(DGH) who provided the Funding support and at last but not least all local and field staff members fortheir help during this study.

References

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[2] R. Marquez, “Las tortugas marinas y nuestro tiempo,”[3] M. Dash and C. Kar, “The Turtle Paradise: Gahirmatha,” p. 295, 1990.

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[4] B. PANDAV, “Conservation and management of olive ridley sea turtle (Lepidochelys olivacea)population along the Odisha coast, Ph.D.thesis.” 2000.

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[11] J. Hendrickson, “Nesting behavior of sea turtles with emphasis on physical and behavioral determi-nants of nesting success or failure,” in Handbook of soil mechanics, soil testing, vol II, pp. 53–57,Elsevier, 1996.

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Nesting Ridleys Need Critical Protection and Its High Nest Successes at Devi Coast Odisha

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