Monitoring presence, abundance and survival probability of the stag beetle, Lucanus cervus, using...

ORIGINAL PAPER

Monitoring presence, abundance and survival probabilityof the stag beetle, Lucanus cervus, using visual and odour-basedcapture methods: implications for conservation

Stefano Chiari • Agnese Zauli • Paolo Audisio • Alessandro Campanaro •

Pier Francesco Donzelli • Federico Romiti • Glenn P. Svensson •

Massimiliano Tini • Giuseppe M. Carpaneto

Received: 31 July 2013 / Accepted: 3 February 2014

� Springer International Publishing Switzerland 2014

Abstract A capture-mark-recapture study on the threa-

tened saproxylic beetle Lucanus cervus was carried out in a

chestnut (Castanea sativa) woodland located in northern

Italy, using visual encounter surveys (VES) as well as

aerial flight interception traps and pitfall traps (PT), both of

which were baited with different odour lures. In total, 111

males and 25 females were captured, and VES was by far

the most efficient method, accounting for 93 % of first

captures, and 95 % of all captures. Stag beetles were not

significantly attracted to any tested odour, and many PT

were damaged by wild boars (Sus scrofa). Flying males

were the most frequent adults observed during the season.

The use of a net is necessary to capture the stag beetles, in

order to evaluate the population parameters and to assess

the local status of threat for the species. Capture data

revealed that body size (i.e. body weight and elytron

length) influences the survival probability of stag beetles,

showing a lower survival probability for larger males. Felt-

tip pen marking on the ventral sclerites of head and

pronotum is a reliable and long lasting method for marking

beetles, as proved by the use of an independent marking

procedure with a small drill. Assessing the presence and

threat status of L. cervus across Europe is urgently needed,

and with no efficient odour-based strategy available, col-

lection of adult beetles, dead or alive, by VES is the most

reliable way to monitor this emblematic species.

Keywords Capture-mark-recapture � Dead wood � Italy �Lucanidae � Population size estimates � Saproxylic

Introduction

Methods for counting animals have evolved over the last

70 years (Andrewartha and Birch 1954) and the study of

demographic parameters, such as population abundance

S. Chiari � P. Audisio � A. Campanaro

Department of Biology and Biotechnologies ‘Charles Darwin’,

Sapienza University of Rome, Via A. Borelli 50,

00161 Rome, RM, Italy

e-mail: [email protected]

A. Campanaro


S. Chiari (&) � A. Campanaro

Centro Nazionale per lo Studio e la Conservazione della

Biodiversita Forestale ‘Bosco Fontana’, Corpo Forestale dello

Stato, Strada Mantova 29, 46045 Marmirolo, MN, Italy


A. Zauli � P. F. Donzelli � F. Romiti � M. Tini �G. M. Carpaneto

Department of Sciences, University Roma Tre, Viale G. Marconi

446, 00146 Rome, RM, Italy


P. F. Donzelli


F. Romiti


M. Tini


G. M. Carpaneto


P. F. Donzelli

Coordinamento Territoriale per l’Ambiente di Verbania per il

Parco Nazionale della Val Grande, Corpo Forestale dello Stato,

Piazza Pretorio 1, 28805 Vogogna, VB, Italy

G. P. Svensson

Department of Biology, Lund University, Ecology Building,

Solvegatan 37, 223 62 Lund, Sweden


123

J Insect Conserv

DOI 10.1007/s10841-014-9618-8

and survival probability, has become one of the most

important issues in conservation biology and landscape

management (Clobert et al. 2001). Biologists have long

known that the smaller the population, the more susceptible

it is to extinction (Shaffer 1981). Consequently, one of the

primary roles of a wildlife monitoring program should be

to track the current status of populations with high accu-

racy so that appropriate management actions can be taken

when substantial changes in population size are detected

(MacKenzie and Nichols 2004).

If population abundance is defined as the number of all

individuals of the same species occupying a particular space

at a particular time (Krebs 2001), including all stages of the

life cycle, then it is very difficult to calculate this parameter

for many holometabolous insects, because adults and larvae

can live in different habitats, with different ecological and

food requirements for periods of time often longer than the

adult stage. Therefore, Tikkamaki and Komonen (2011)

suggested studying only adults when monitoring the status

and extinction risk of insect populations. Moreover, in

species where adults can be easily captured and marked, the

capture-mark-recapture (CMR) approach is suitable for

quantifying population characteristics (Amstrup et al.

2005). During the last decade, several CMR studies have

been performed on large threatened beetles to estimate

population size using various methods for capturing adults,

including odour-baited traps and visual surveys (Ranius

2001; Larsson and Svensson 2009; Tikkamaki and Komo-

nen 2011; Drag et al. 2011; Chiari et al. 2013).

Saproxylic invertebrates, i.e. organisms dependent on

fungal decay of wood in living or dead trees, or on other

saproxylic organisms during at least some part of their life

cycle (Speight 1989; Alexander 2008), have been identified

as one of the most threatened guilds of the European fauna

(Speight 1989; Berg et al. 1994; Nieto and Alexander

2010). Their decline is mostly due to intensive commercial

forestry and changed agricultural management practices,

which have decreased the amount and quality of dead wood

(Davies et al. 2008). The European stag beetle, Lucanus

cervus (Linnaeus, 1758) (Coleoptera: Lucanidae), is a

saproxylic beetle whose larva develops underground and

feeds on decaying wood of stumps and roots from a wide

range of broad-leaved trees and shrubs (Percy et al. 2000).

This species, listed in the IUCN Red List of Threatened

Species as ‘‘near threatened’’, in the EU Habitats Directive

as a priority species of community interest (Appendix II)

(Nieto and Alexander 2010) and in the Bern Convention

(Appendix III), is indubitably the most charismatic and

popular saproxylic insect in Europe. The stag beetle was

also mentioned as one of the most emblematic flagship

species for biological conservation in Europe and a focal

species for the conservation of suitable habitats for sapr-

oxylic beetles (Thomaes et al. 2008). Despite that, it is

thought to be declining across much of its European range

(Harvey et al. 2011a) and no CMR study has been per-

formed previously to analyse population parameters of this

species.

The topic of how to capture stag beetles to gain infor-

mation about population parameters has been discussed for

decades. Many investigators have studied the attraction of

this beetle to various odour lures, either in the laboratory or

under natural and semi-natural conditions (woodlands and

urban gardens, respectively) obtaining various levels of

behavioural response (Brustel and Clary 2000; Chapman

et al. 2002; Krenn et al. 2002; Fremlin and Hendriks 2011;

Jansson 2011; Harvey et al. 2011b; Vrezec and Kapla 2007;

Vrezec et al. 2006, 2007). For example, promising data on

short-range attraction to several odour sources under labo-

ratory conditions did not translate into large captures of

adults in the field when such odours were used in aerial

flight interception traps (AFIT) or pitfall traps (PT) (Harvey

et al. 2011b). Such contradictory results could be an effect

of low density of beetles in the study area, or low level of

long-range attraction to the odour sources applied. Ideally,

the use of feeding resources and attractive compounds as

lures should be compared with other methods for monitor-

ing beetles as well with as available elements present in

nature in a certain area, in order to reach valid conclusions

concerning the reliability of the potential attractants, and to

assess an effective method for monitoring adults of L.

cervus across its entire distributional range.

In this study, a CMR approach on L. cervus was per-

formed in northern Italy, testing different capture methods

and odour lures to increase the current knowledge of the

threat status of the species and survival probability of

individual beetles in that region, and to improve conser-

vation programmes through the optimization of field effort

and costs for population monitoring. In particular, four

specific questions were addressed: (1) What is the best

method for capturing stag beetles in nature and monitoring

populations among the ones tested in this study? (2) Is

CMR an applicable method to evaluate stag beetle popu-

lation abundance? (3) Does the body size (as a function of

sex, body weight and elytron length) influence the survival

probability of the individuals? (4) Is felt-tip pen marking a

long lasting method for coding individual beetles to ensure

proper identification in case of subsequent recapture?

Materials and methods

Study area and field work

The study area was an old-growth chestnut (Castanea sati-

va) woodland situated in Monterosso (UTM Zone 32 T,

WGS84, 463232 5088073, between 329 and 622 m a.s.l.), a

J Insect Conserv

123

hill located near Verbania, Piedmont (northern Italy).

Monterosso is a woodland area that includes some human

settlements, i.e. a small village (Cavandone) and scattered

country houses. The woodland is managed as a stand of high

chestnut trees of different ages, regrown over an ancient

coppice; tree density is variable with an open canopy near

the tracks and in clearings. Deadwood is abundant and

represented by stumps, fallen logs and small wood debris.

Adults of L. cervus were sampled using both traps and

visual inspection of dirt tracks and clearings (visual

encounter surveys, hereby VES like in Chiari et al. 2013).

The trap types were two: AFIT and PT, the same as in

Harvey et al. (2011b). The AFIT were suspended from tree

branches at 2–4 m height, and the PT were buried with the

opening at soil level, covered with a wooden roof to pre-

vent predator attack (Fig. 1). In 2012, 35 trap replicates

were set along three 3 m wide dirt tracks (Fig. 2), and from

28th May to 27th July the replicates were checked every

second day, from 15:00 to 22:30. Each replicate contained

one AFIT and one PT, both baited with the same potential

attractant, and one unbaited trap of each type, serving as

control. Therefore 70 baited traps were set (7 AFIT and 7

PT, each type with 5 potential attractants) and 70 control

traps (one for each baited trap), for a total of 140 traps. The

traps were set 2–10 m apart (Harvey et al. 2011b; Svensson

and Larsson 2008) (Fig. 1). Ginger root, cherry juice,

maple syrup, mango juice and red wine were tested as

potential attractants, chosen among those used by Harvey

et al. (2011b). For solid and liquid substances, 20 g or

20 ml samples were used respectively (Harvey et al.

2011b), and the lures were replaced every two checks (i.e.

5 days). To avoid position effects, the relative positions of

AFITs within replicates were exchanged every two checks,

simultaneously with the replacing of lures, whereas for PTs

only the roofs, with the annexed lure holders, were

exchanged (Svensson et al. 2011; Harvey et al. 2011b).

Each replicate was separated by at least 100 m to guarantee

the spatial independence between presumed different lure

effects (Svensson et al. 2011). The maximum distance

among replicates was about 2500 m, which is shorter than

the maximum dispersal distance expected for males (Rink

and Sinsch 2007). The sequence of potential attractants in

each set of five replicates was randomly chosen (without

replacement), repeating the first extraction if the potential

attractant was the same of the last of the previous set,

avoiding two consecutive replicates with the same attrac-

tant in order to make the sampling more heterogeneous

across the landscape (Fig. 2). Each trap was marked and

geo-referenced using a Garmin GPS (MAP 60 CSX). The

VES were carried out by two operators who walked along

both sides of the dirt tracks, during trap checking, and

crossing two clearings (Fig. 2). On the whole, the pathway

measured 8.5 km. Stag beetles observed during the VES

were captured by hand when possible, i.e. when the beetles

were on the ground, trunks or rocks. An entomological net

(http://www.insectnet.eu/), consisting of a circular frame

(50 cm diameter) and a telescopic handle (up to 199 cm),

was used to catch stag beetles in flight. In addition, all stag

beetle body fragments, mostly remains of predation

(Campanaro et al. 2010), were collected. The order in

which operators surveyed the three dirt tracks (e.g. A, B

and C) was systematically changed at each survey,

repeating the permutation of the possible combinations of

the dirt tracks (e.g. ABC, ACB, BCA, BAC, CAB, CBA,

and so on) until the end of the study period.

Upon first capture, each stag beetle was weighed, mea-

sured and then marked with an individual identification

code, following a double procedure: (1) by an indelible

felt-tip pen (Uni Paint Marker, medium-fine paint marker

2.2–2.8 mm line ø, in red and white colours) on the ventral

sclerites of head and pronotum (Campanaro et al. 2011);

(2) by a small drill (Dremel Lithium Cordless 8000JE) on

both elytra (Chiari et al. 2013). The double marking pro-

cedure of each beetle increased the probability to identify

the fragments of previously captured individuals, and was

also carried out to test the durability of the felt-tip pen

mark. If a recaptured beetle showed only the mark on the

elytra it was assumed that the felt-tip pen mark on the head

and/or pronotum had been lost. Finally, the estimate of

marking loss can be used to correct population estimates

(Sutherland 2006). The body mass was measured using a

portable balance (PESOLA AG, Switzerland) (precision

10 mg). The length of the elytral suture (elytron length)

was measured from the base of the scutellum to the apex of

the elytra, in the midline, with a calliper rule (precision

0.05 mm). The elytron length was preferred to the most

common body length since total body size (from clypeus to

pygidium) is not a very precise measure of size due to the

mobility of segments (Juliano 1986). The sex of beetles

was determined by the shape of the mandibles, which

shows a strong sexual dimorphism in this species (Fran-

ciscolo 1997). After the marking procedure, and successive

captures, beetles were released at the place of capture. No

beetle appeared to be injured by the marking procedure and

no discernible leak of haemolymph was observed.

Data analysis

Capture data, efficiency of monitoring methods and body

measurements

Differences between male and female captures including

all three monitoring methods were tested by the Yates

corrected v2 test, and differences in number of captures

(both sexes) between odour-baited and unbaited traps

(AFIT and PT combined) were tested by the Fisher’s exact

J Insect Conserv

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http://www.insectnet.eu/

test. In addition, the Kruskal–Wallis ANOVA was per-

formed to compare the total number of captures between

monitoring methods (male and female data pooled). The

Shapiro test was used to test whether body measurements

data were normally distributed. The assumption of equal

variances for data on body mass and elytron length in both

males and females was verified by the Brown-Forsythe test,

and subsequent analysis of sex-related body size values

was performed using the Mann–Whitney U test. The

Pearson correlation coefficient was used to analyse the

relation between body mass and elytron length for both

sexes of beetles. All analyses were performed using

STATISTICA 7.0 (StatSoft Inc.), with a significance level

of 0.05 to reject the null hypothesis.

Population size and survival estimates

The mark-recapture data were analysed in order to inves-

tigate some aspects of the demography, size and survival

probability of the studied stag beetle population. Estimates

were calculated using information only from VES captures.

Overall population size and survival probability esti-

mates were performed for both sexes separately. The Jolly-

Seber method (POPAN parameterization) was used to

estimate the total population size, and the Cormack-Jolly-

Seber method (Jolly 1965; Southwood 1978) was used to

estimate and model the survival probability. Both methods

are suitable for analyses of open populations, and they

allow estimations of three parameters: (1) the survival

Fig. 1 Detail of aerial flight

interception trap in place, with

lure in the upper chamber, and

diagram representing one of the

35 trap replicates. Flowerpots

were used as pitfall traps, buried

with the opening at soil level

with lure chamber attached in

the middle of the wooden roof

Fig. 2 Overview of the 35 trap replicates located along three dirt

tracks (black lines), which cross the woodlands where two operators

carried out the visual encounter surveys of Lucanus cervus. Black

symbols correspond to the use of different potential attractants (circle

cherry juice, square ginger, triangle mango juice, pentagon maple

syrup, hexagon red wine). Open circles around the black symbols

indicate the position of traps in two clearings

J Insect Conserv

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probability (/), (2) the capture probability (p), (3) the total

population size (NT). The first two parameters can be

constant (.), or can respond over time in a linear manner (t).

The survival probability was modelled in two ways: (1)

assuming that the parameter is a function of body mass

(BM) or of elytron length (EL) of a beetle at the time it was

first marked and released; (2) assuming that the parameter

is maximized for beetles having a mean body mass

(BM,BM^2) or a mean elytron length (EL,EL^2). These

analyses were performed using the program MARK (White

and Burnham 1999). For each model, differing in param-

eterization, MARK computed the AICc, a measure of

goodness of fit of the model combining likelihood and

complexity (Burnham and Anderson 2002). The model

with the highest support was assumed to be the one with

the lowest value of AICc (Burnham and Anderson 2002). A

model is usually considered plausible if DAICc \ 2

(Burnham and Anderson 2002). Finally, the coefficient of

variation (CV) was calculated as the standard error divided

by the number of individuals estimated and indicates the

precision of the population size estimate.

Results

Capture data

In total, 153 captures of 136 individuals (111 males, 25

females) of L. cervus were observed (Table 1). Of 17

recaptures, 14 were carried out with the same method and

lure and in the same replicate (or during VES), whereas

two took place with a different method and lure, and only

one with the same method but with a different lure, all in

the same replicate. The male captures outnumbered female

captures (v12 = 62.771, p \ 0.01). All recaptured beetles

were recaptured only once, with a recapture rate of 13 %

(15/111) for males and 8 % (2/25) for females. The mean

time between recaptures was 5.4 days for males and

6.0 days for females, with a maximum time period of

14 days for males and 8 days for females between cap-

tures. A low proportion 3 % (4/136) of the marked beetles

(all males) were found dead, all during VES. Most of the

captures were performed between the middle of June and

the middle of July, with a peak around 25th June (Fig. 3).

Monitoring methods

There was a highly significant difference in the number of

L. cervus captured with the different monitoring methods

(Kruskal–Wallis ANOVA, df = 12, N = 175, H =

27.707, p = 0.006). The highest rank sum (best perfor-

mance) was reached by VES (Sum of Ranks = 3278.500),

discriminating this method as by far the best in capturing

this species (Fig. 3). In contrast, there was no difference in

captures between odour-baited and unbaited traps for any of

the two trapping methods (Fisher’s exact test, p = 1.000).

Body measurements

The elytron was significantly longer in males (range:

17.16–29.25 mm) than females (range: 17.89–24.16 mm)

(median: males, 22.48 mm; females, 21.25 mm; U = 905.0,

p = 0.007). In contrast, there was no significant difference

in the median body mass between males (range:

0.80–4.50 g) and females (range: 1.30–3.20 g) (median:

males, 2.20 g; females, 2.10 g; U = 1241.0, p = 0.410). In

both sexes there was a highly significant correlation between

elytron length and body mass (Pearson Correlation Coeffi-

cient: females, r2 = 0.617, rp = 0.785, p = 0.000; males,

r2 = 0.876, rp = 0.936; p = 0.000) (Fig. 4).


The Jolly-Seber (POPAN parameterization) estimates of

population size for males and females were 2207 (NT:

confidence interval 1283–3132; CV = 0.21) and 747 indi-

viduals (NT: confidence interval 208–1284; CV = 0.37),

respectively.

The best-fitting Cormak-Jolly-Seber models for male

survival probability in relation to body mass resulted in two

plausible models (i.e. DAICc \ 2) (Table 2). In the first

model the male survival probability was constant in time (w/

(.)p(.) = 0.49), while in the second one it was dependent on

body mass (w/(BM)p(.) = 0.26). Heavier males had a lower

Table 1 Summary of capture-mark-recapture data obtained during

the study of Lucanus cervus in northern Italy with different moni-

toring methods and lures

Method Bait Marked beetles

(#/$)

Capture events

(#/$)

AFIT Cherry juice – –

Ginger root – –

Mango juice 2/0 2/0

Maple syrup – –

Red wine 5/0 5/0

Control 2/0 2/0

PT Cherry juice – –

Ginger root – –

Mango juice – 1/1

Maple syrup – –

Red wine – –

Control 0/1 0/1

VES 102/24 116/25

AFIT aerial flight interception traps, PT pitfall traps, VES visual

encounter surveys

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123

survival probability (Fig. 5a). For females three models

were equally good (Table 2). In the first model the female

survival probability was dependent on body mass in a linear

way (w/(BM)p(.) = 0.38) (Fig. 5b), the second model sup-

ported the normalizing selection (w/(BM,BM^2)p(.) = 0.36),

indicating that females with a body mass near the mean value

were favoured, and the third model suggested that female

survival probability was constant over time (w/

(.)p(.) = 0.26).

The best-fitting Cormak-Jolly-Seber models for the sur-

vival probability of males in relation to elytron length

resulted in two plausible models (Table 3). In the first model

the male survival probability was constant in time (w/

(.)p(.) = 0.51), while in the second one it was dependent on

elytron length (w/(EL)p(.) = 0.23). Males with longer elytron

length had a lower survival probability. For females, there

was only one fitting model (Table 3) which strongly sup-

ported the normalizing selection (w/(EL,EL^2)p(.) = 0.65),

indicating that females with the elytron length near the mean

value were favoured.

Methodological issues

During the first four surveys, on average 30 % of the PTs

per day were found broken by wild boar (Sus scrofa), with

no difference among baited and unbaited traps (v12 = 0.02,

p [ 0.05). Therefore, after the fifth survey, PTs were

removed from 26 of the 35 replicates and left only in the

more anthropized zone not reachable by wild boars.

The 95 % (134/141) of VES captures, including dead

individuals, were performed from 20:00 to 22:00, mostly in

two large clearings (132 out of 141) (Fig. 2). The majority

74 % (101/136) of VES captures of living adults were

performed using a net, and captures of living females by

hand or net were significantly lower than those of males

(v12 = 6.140, p = 0.01). All recaptured beetles (17 out of

136) showed the felt-tip pen mark on the ventral sclerites of

head and pronotum.

Discussion

Capture data, monitoring methods and body

measurements

The threatened saproxylic beetle L. cervus was caught more

abundantly than expected for a single sampling season. In a

study conducted in England over 4–5 years, using a similar

set of methods, 55 individuals were captured with odour-

baited AFIT and PT, and 153 individuals were recorded

during road transect surveys (Harvey et al. 2011b), indi-

cating smaller populations in that region. This is probably

due to substantial differences between the habitat investi-

gated in our study and in Harvey et al. (2011b): chestnut

woodland in Italy versus urban gardens in England.

Significantly more males than females were captured

and marked, but the recapture rate was low, independently

Fig. 3 Daily captures events of Lucanus cervus performed by different monitoring methods and lures (AFIT aerial flight interception traps, PT

pitfall traps, VES visual encounter surveys)

Fig. 4 Correlations between elytron length and body mass of adult

males and females stag beetles measured during the capture-mark-

recapture study

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123

of sex, as all recaptured beetles were recaptured only once.

This suggests that is not easy to recapture adult stag beetles

and the low recapture rate could make estimates of popu-

lation parameters less precise. This is a major problem, but

estimates of population parameters are absolutely neces-

sary in red-list assessment and population monitoring of

threatened species (Tikkamaki and Komonen 2011). The

biased capture-recapture sex ratio observed for L. cervus in

this study, and in previous ones (Table 4), seems to be an

artefact mostly due to the sampling method used and does

not necessarily reflect a true difference in the number of

males and females present, as documented also in other

beetles and insects since about 30 years (Shibata 1986;

Kuussaari et al. 1996; Stoks 2001; Ranius 2001; Larsson

and Svensson 2009; Chiari et al. 2013). It is still not clear

whether the effective sex ratio of L. cervus is even, and

further studies are needed to clarify the male/female pro-

portion because this parameter could affect the reproduc-

tive rate and the level of inbreeding (Fitz-Earle and Barclay

1989; Werren 1993; Heimpel and Lundgren 2000).

In this study, VES was by far the best method to capture

both males and females of L. cervus, accounting for 93 %

of first captures, and 95 % of all captures. In contrast, just

few catches were observed in odour-baited traps and adults

were not attracted at significant numbers to any of the

odour sources tested. These results are thus in agreement

with those by Harvey et al. (2011b), and confirm that the

few captures in odour-baited traps in England was not due

to low population densities at the study site, but instead a

true lack of attraction of beetles to the test odours applied.

Thus, there is still no efficient odour lure available for

monitoring stag beetle populations. Instead, visual

encounters of living adults, collection of dead individuals

and body fragments (Harvey and Gange 2006; Campanaro

et al. 2010; Campanaro and Bardiani 2012), and road

transect surveys (Harvey et al. 2011b) are currently the

most reliable methods to study population trends in this

species. Moreover, these methods are inexpensive and

easily applicable by volunteers to screen for presence and

abundance of L. cervus.

Fig. 5 Survival probability (/) of the stag beetle, males (a) and

females (b), modeled in relation to body mass (BM) using the

Cormack-Jolly-Seber method in the program MARK. Used model /(BM) p(.). The black line indicates the predicted survival probability,

the grey dotted lines indicate the 95 % confidence intervals

Table 2 Summary of model selection statistics for the Cormak-Jolly-Seber models used to estimate survival probability (/) and capture

probability (p), in realtion to the body mass (BM) and to the mean body mass (BM,BM^2)

Males Females

Model K -2Log (L) DAICc w Model K -2Log (L) DAICc w

/(.) p(.) 2 115.37 0.00 0.49 /(BM) p(.) 2 7.51 0.00 0.38

/(BM) p(.) 3 91.69 1.27 0.26 /(BM,BM^2) p(.) 3 5.01 0.13 0.36

/(t) p(.) 12 95.62 3.20 0.10 /(.) p(.) 2 8.31 0.81 0.26

/(BM,BM^2) p(.) 4 87.88 3.31 0.09 /(t) p(.) 9 4.50 23.28 0.00

/(.) p(t) 14 114.42 4.42 0.05 /(t) p(t) 9 4.50 23.28 0.00

/(t) p(t) 18 114.52 11.53 0.00 /(.) p(t) 14 4.82 67.41 0.00

K represents the number of parameters in the model and -2Log (L) is twice the negative log-likelihood value. Relative AICc (Small sample

Akaike Information Criteria) values and Akaike weight, w, are reported for each model (DAICc represents the difference in AICc value relative

to the top model, Burnham and Anderson 2002). Survival probability (/) and capture probability (p) may be constant (.) or may vary between

sampling occasions (t)

J Insect Conserv

123

As in seven other European countries where stag beetle

body size was studied (Harvey et al. 2011a), also in

northern Italy males were longer than females. Surpris-

ingly, there was no significant difference in body mass

between sexes. This result could be probably due to the

largest range of body mass registered in males (Fig. 4), that

makes median values of males and females very similar

and does not reflect the documented body size dimorphism

of this species (Rink and Sinsch 2007, 2011).


The population size estimates (obtained from VES captures

only) differed between males and females, and also showed

a variable coefficient of variation. This information sug-

gests that L. cervus in Italy could be more abundant than

other large threatened saproxylic beetles, e.g. Osmoderma

eremita (Chiari et al. 2013). However, due to the suspected

decline across much of its European range (Harvey et al.

2011a), broad monitoring sampling programs are needed

across the distribution range of L. cervus in order to obtain

reliable information about local extinction risks for this

emblematic species.

For both sexes, body size influences the survival prob-

ability. However, while for males the increase in body size

corresponds to a decrease in survival probability, for

females the explanation of how body size may affect sur-

vival probability is not so straightforward because both the

linear and the normalizing selection are equally well sup-

ported. L. cervus exhibits a wide variation in body size,

particularly in males, which is related to mating success,

larval diet and environmental constraints (Harvey and

Gange 2006; Rowe and Ludwig 1991). The reduction in

Table 3 Summary of model selection statistics for the Cormak-Jolly-Seber models used to estimate survival probability (/) and capture

probability (p), in realtion to the elytron length (EL) and to the mean elytron length (EL,EL^2)

Males Females

Model K -2Log (L) DAICc w Model K -2Log (L) DAICc w

/(.) p(.) 2 115.37 0.00 0.51 /(EL,EL^2) p(.) 3 3.02 0.00 0.65

/(EL) p(.) 3 114.826 1.57 0.23 /(EL) p(.) 2 8.27 2.61 0.18

/(t) p(.) 12 95.62 3.20 0.10 /(.) p(.) 2 8.31 2.66 0.17

/(EL,EL^2) p(.) 4 114.48 3.37 0.09 /(t) p(.) 9 4.50 25.13 0.00

/(.) p(t) 14 91.69 4.42 0.06 /(t) p(t) 9 4.50 25.13 0.00

/(t) p(t) 18 87.88 11.53 0.00 /(.) p(t) 14 4.82 69.26 0.00

K, -2Log (L), DAICc and are presented in Table 2. Survival probability (/) and capture probability (p) may be constant (.) or may vary between

sampling occasions (t)

Table 4 Comparison of six studies on the Lucanus cervus across Europe

Harvey and

Gange (2006)

(OCC)

Rink and

Sinsch (2007)

(RAD)

Hawes (2008)

(CMR)

Campanaro

et al. (2011)

(OCC)

Harvey et al. (2011a)

(CMR)

Present study

(CMR)

Country England Germany England Italy England Italy

Study period 1998–2004 2003–2005 2006 2008 2004* or 2005–2008 2012

Study method/s Collection of dead

individuals and

body fragments

Not specified PT

Hand

Net

Collection of dead

individuals and

zbody fragments

AFIT

PT

RTS

AFIT

PT

VES

No. of beetles

Total 1255 56 138 306 55, 153* 10, 126**

Male 569 18 100 290 30, unknown* 9, 102**

Female 686 38 38 16 25, unknown* 1, 24**

Sex ratio 1:1 Female-biased Male-biased Male-biased 1:1, female-biased* Male-biased

For Harvey et al. (2011a) and for the present study it was possible to distinguish between beetles captured with different methods (* = by RTS;

** = by VES; no specifications for beetles captured by AFIT and PT

CMR capture-mark-recapture, OCC occurrence, RAD radiotelemetry; AFIT air flight interception traps, PT pit fall traps, RTS road transect

surveys, VES visual encounter surveys

J Insect Conserv

123

survival probability of larger males could be due to an

increase in predation rate, mostly inflicted by corvids,

which hunt on sight and are the most common predators of

L. cervus adults across Europe (Harvey et al. 2011a), and to

higher metabolic costs due to the larger dimensions and

related behaviours. In many species of insects that have a

marked male dimorphism, the different ‘types’ of males

have developed alternative reproductive strategies (Emlen

and Nijhout 2000). In the stag beetle the intensity of

aggressive behaviour of males is highly dependent on their

body size, and larger males are generally more aggressive

and prone to fight (Lagarde et al. 2005). Moreover, Har-

dersen et al. (2011) collected remnants of the largest males

mostly at the beginning of the season (mid May) and the

average size of collected males thereafter decreased, sug-

gesting that the threshold in body size, which determines

the morph expression of biggest males with large mandi-

bles, shifts along the season. In the female, body size may

contribute to fecundity, with larger females producing

more eggs (Harvey et al. 2011a), but Harvey and Gange

(2006) reported that the ratio between male and female size

is a limiting factor, which influences the mating success in

laboratory tests. It is not clear how the fitness regulates the

body size of L. cervus individuals with respect to a geno-

type or to a phenotype, both at larval and adult stages, and

future research should aim at gaining a quantitative

understanding of this phenomenon.

Methodological issues

The use of PT is a potentially dangerous method for cap-

turing stag beetles in woodlands because the wooden roof

is not sufficient to prevent predator attack and the wild boar

(S. scrofa) destroys these traps, irrespectively if they are

baited with odour lures or not. The wild boar is reported as

one of the major predators of L. cervus larvae (Harvey et al.

2011a), and by using PT it could became a predator also of

adult beetles and the method may thus influence the sur-

vival probability of populations. For this reason most of the

PT were removed from the experiment and left only in the

most anthropized area, where wild boars were not present.

In order to prevent an increased predation risk and mor-

tality rate of adult stag beetles, PT should not be used in

areas where there is a high density of potential predators

such as wild boar, badger (Meles meles), foxes (Vulpes

vulpes) and hedgehog (Erinaceus sp.).

Most of the captures were performed at or just after

sunset, from 20:00 to 22:00, and in two clearings, identified

as the places where beetles were more active in flight. This

result supports the statements of a stag beetle flight peak

activity at dusk (Hawes 2008) and of the ‘hot spots’ phe-

nomenon at small scale (Pratt 2000) with an aggregated

distribution of occurrence at all spatial scales (Harvey et al.

2011a). However, it still remains uncertain if the ‘hot

spots’ phenomenon is due to a restricted availability of

suitable habitat and/or to aggregation of individuals asso-

ciated with mating.

Captures of males were higher than those of females

regardless of sex-related behaviour, such as flight in the

male and seeking behaviour on the ground for the female

(Harvey and Gange 2006; Rink and Sinsch 2011). No

female was captured by AFIT but surprisingly almost the

same numbers of female captures were performed by hand

(12 out of 27) or by net (13 out of 27). In any case, for a

CMR study it is necessary to use a net in order to capture

flying beetles, which are the most frequent adults observed

during the season.

Applying individual identification codes with an indel-

ible felt-tip pen was a reliable method to mark adults of L.

cervus, because such codes were found on all recaptured

beetles, as confirmed by the independent drill marks.

Therefore, the less costly and invasive tip pens may be

considered the most favourable method for mark-recap-

turing stag beetles in monitoring programs.

Conclusions and implications for conservation

Due to the threat status of the stag beetle, monitoring

programs to assess its presence and population sizes across

Europe are urgently needed. The present paper was con-

ceived in a poor status of knowledge about the phenology

of the stag beetle in Italy, still based on anecdotal infor-

mation. For this reason, we planned an intensive fieldwork

to identify the time interval when the species is easy to

detect in nature and to prevent the loss of information that

could bias an experiment. Our research was mostly aimed

to verify the usefulness of baited traps (a costly and time-

consuming method) in comparison with simple visual

surveys. In a previous study (Harvey et al. 2011b), traps

baited with either ginger or mango had a significant

attraction effect on both sexes of L. cervus when tested in

short-range laboratory experiments, but did not attract a

significant number of adults when applied in the field. In

the present study, the attractiveness of all the substances

used was very low and not useful for the stag beetle pop-

ulation monitoring. Therefore, until now the use of traps

baited with odour attractants have not helped in sampling

efforts to gather quantitative information on L. cervus

population demography. In addition, PT may expose the

stag beetles to predation by mammals, mainly wild boars.

The road transect surveys can not be a universal method,

because outside England the stag beetle is mostly present in

woodland areas (Harvey et al. 2011a). Therefore, the col-

lection at dusk of either living adults or their remnants by

VES (e.g. walking along transects or stationing in flying

sites) seems to be the most cost-efficient and effective

J Insect Conserv

123

Standard

Evidenziato

Standard

Evidenziato

Standard

Evidenziato

Standard

Evidenziato

Standard

Evidenziato

Standard

Evidenziato

method (i.e. optimal, sensu Chiari et al. 2013) to monitor

the presence and/or abundance of this species across its

distributional range. In order to carry out a CMR study,

collectors should have an entomological net to capture

flying adults and surveys should be carry out between

20:00 and 22:00. Owing to the documented presence of

‘hot spots’, i.e. small areas where a lot of individuals are

aggregated, many walking transects should be carried out,

repeatedly during the season, in order to limit the proba-

bility of reporting false absence of the stag beetle or

inaccurate population parameters estimates, as this species

is usually detected in low numbers, and is only active

during a short period of warm nights in June and July

(Smith 2003; Harvey et al. 2011a). Due to its role as

flagship and focal species, the monitoring of L. cervus

deserves high priority for biodiversity conservation in

Europe, because if measures are taken to protect this beetle,

many other saproxylic organisms in the same habitat will

be conserved. Precautionary actions are needed to reduce

the rate of predation by corvids, such as the hooded crow

(Corvus corone cornix) whose population density is

increasing with woodland fragmentation (Andren 1992;

Sodhi and Ehrlich 2010), and to reduce the risk of local

extinctions of small stag beetles populations. Therefore,

forest management should be oriented to avoid woodland

fragmentation, control hooded crow populations and

increase the amount and quality of stumps and dead wood

where stag beetle populations are present.

Acknowledgments This study was partially supported by the pro-

ject ‘‘Studio ecologico preliminare su specie saproxiliche della

Direttiva Habitat, nel Parco Nazionale della Val Grande’’ financed by

the ‘‘Parco Nazionale della Val Grande’’. We thank the staff of the

park, in particular Tullio Bagnati (Director) and Cristina Movalli,

(Promoter of Nature Conservation and Management), who supported

the project. A special thanks is given to the agent of the State Forestry

Corps, Simone Torniai, for field assistance and precious help. The

work of S.C. is supported by the VABAS project. G.P.S. is supported

by the Swedish Research Council Formas.

References

Alexander KNA (2008) Tree biology and saproxylic Coleoptera:

issues of definitions and conservation language. Rev Ecol (Terre

Vie) 10:9–13

Amstrup SC, McDonald TL, Manly BFJ (2005) Handbook of capture-

recapture analysis. Princeton University Press, Princeton

Andren H (1992) Corvid density and nest predation in relation to

forest fragmentation: a landscape perspective. Ecology

73:794–804

Andrewartha HG, Birch LC (1954) The distribution and abundance of

animals. Univ. of Chicago Press, Chicago, Illinois

Berg A, Ehnstrom B, Gustafsson L, Hallingback T, Jonsell M,

Weslien J (1994) Threatened plant, animal, and fungus species in

Swedish forests—distribution and habitat associations. Conserv

Biol 8:718–731

Brustel H, Clary J (2000) ‘Oh, cette Gresigne!’, Acquisitions

remarquables pour cette foret et le sud-ouest de la France:

donnees faunistiques et perspectives de conservation (Coleop-

tera), (premier supplement au catalogue de Jean Rabil, 1992,

1995). Bull Soc Entomol Fr 105:357–374

Burnham KP, Anderson DR (2002) Model selection and multimodel

inference: a practical information—theoretic approach. Springer,

Berlin

Campanaro A, Bardiani M (2012) Walk transects for monitoring of

Lucanus cervus in an Italian lowland forest. Saproxylic beetles in

Europe: monitoring, biology and conservation. Studia Forestalia

Slovenica, pp 17–22

Campanaro A, Hardersen S, Toni I, Grasso DA (2010) Monitoring of

Lucanus cervus by means of Remains of Predation (Coleoptera:

Lucanidae). Entomol Gen 33:79–89

Campanaro A, Bardiani M, Spada L, Carnevali L, Montalto F,

Antonini G, Mason F, Audisio P (2011) Linee guida per il

monitoraggio e la conservazione dell’entomofauna saproxilica.

Quaderni Conservazione Habitat, 6. Cierre Grafica, Verona,

p 8. ? CD-ROM

Chapman JW, Birkett MA, Pickett JA, Woodcock CM (2002)

Chemical ecology and conservation of the stag beetle, Lucanus

cervus. Chemical communication: from hormones to semio-

chemicals. Comp Biochem Physiol A 132:63–70

Chiari S, Zauli A, Mazziotta A, Luiselli L, Audisio P, Carpaneto GM

(2013) Surveying an endangered saproxylic beetle, Osmoderma

eremita, in Mediterranean woodlands: a comparison between

different capture methods. J Insect Conserv 17:171–181

Clobert J, Danchin E, Dhondt AA, Nichols JD (2001) Dispersal.

Oxford University Press, Oxford

Davies ZG, Tyler C, Stewart GB, Pullin AS (2008) Are current

management recommendations for saproxylic invertebrates

effective? A systematic review. Biodivers Conserv 17:209–234

Drag L, Hauck D, Pokluda P, Zimmermann K, Cizek L (2011)

Demography and dispersal ability of a threatened saproxylic

beetle: a mark-recapture study of the rosalia longicorn (Rosalia

alpina). PLoSONE 6:e21345. doi:10.1371/journal.pone.0021345

Emlen DJ, Nijhout F (2000) The development and evolution of

exaggerated morphologies in insects. Rev Ecol (Terre Vie)

45:661–708

Fitz-Earle M, Barclay HJ (1989) Is there an optimal sex ratio for

insect mass rearing? Ecol Model 45:205–220

Franciscolo ME (1997) Coleoptera Lucanidae. Collana ‘‘Fauna

d’Italia’’,Volume XXXV, Calderini, Bologna

Fremlin M, Hendriks P (2011) Sugaring for stag beetles—different

feeding strategies of Lucanus cervus and Dorcus parallelipipe-

dus. Bull Amat Entomol Soc 70:57–67

Hardersen S, Macagno ALM, Sacchi R, Toni I (2011) Seasonal

constraints on the mandible allometry of Lucanus cervus

(Coleoptera: Lucanidae). Eur J Entomol 108:461–468

Harvey DJ, Gange AC (2006) Size variation and mating success in the

stag beetle, Lucanus cervus L. Physiol Entomol 31:218–226

Harvey DJ, Gange AC, Hawes CJ, Rink M (2011a) Bionomics and

distribution of the stag beetle, Lucanus cervus (L.) across

Europe. Insect Conserv Diver 4:23–38

Harvey DJ, Hawes CJ, Gange AC, Finch P, Chesmore D, Farr I

(2011b) Development of non-invasive monitoring for larvae and

adults of the stag beetle, Lucanus cervus. Insect Conserv Diver

4:4–14

Hawes CJ (2008) The stag beetle Lucanus cervus (Linnaeus, 1758)(Coleoptera: Lucanidae): a mark-release-recapture study under-

taken in one United Kingdom residential garden. Rev Ecol

(Terre Vie) 63:131–138

Heimpel GE, Lundgren JG (2000) Sex ratios of commercially reared

biological control agents. Biol Control 19:77–93

J Insect Conserv

123

http://dx.doi.org/10.1371/journal.pone.0021345

Jansson N (2011) Attraction of stag beetles with artificial sap in

Sweden. Bull Amat Entomol Soc 70:51–56

Jolly GM (1965) Explicit estimates from capture-recapture data with

both death and immigration-stochastic model. Biometrika

52:225–247

Juliano SA (1986) Food limitation of reproduction and survival for

populations of Brachinus (Coleoptera: Carabidae). Ecology

67:1036–1045

Krebs CJ (2001) Ecology: the experimental analysis of distribution

and abundance, 5th edn. Benjamin Cummings, San Francisco,

California

Krenn HW, Pernstich A, Messner T, Hannappel U, Paulus HF (2002)

Kirschen als Nahrung des mannlichen Hirschkafers, Lucanus

cervus (Linnaeus 1758) (Lucanidae: Coleoptera). Entomologi-

sche Zeitschrift Stuttgart 112:165–170

Kuussaari M, Nieminen M, Hanski I (1996) An experimental study of

migration in the Glanville fritillary butterfly Melitaea cinxia.

J Anim Ecol 65:791–801

Lagarde F, Corbin J, Goujon C, Poisbleau M (2005) Polymorphisme

et performances au combat chez les males de Lucane cerf-volant

(Lucanus cervus). Rev Ecol (Terre Vie) 60:127–137

Larsson MC, Svensson GP (2009) Pheromone monitoring of rare and

threatened insects: exploiting a pheromone-kairomone system to

estimate prey and predator abundance. Conserv Biol 23:

1516–1525

MacKenzie DI, Nichols JD (2004) Occupancy as a surrogate for

abundance estimation. Anim Biodivers Conserv 27:461–467

Nieto A, Alexander KNA (2010) European red list of saproxylic

beetles. Publications Office of the European Union, Luxem-

bourg, Belgium

Percy C, Bassford G, Keeble V (2000) Findings of the 1998 national

stag beetle survey. People’s Trust for Endangered Species,

London

Pratt CR (2000) An investigation into the status history of the stag

beetle Lucanus cervus Linneus (Lucanidae) in Sussex. Coleopt

9:75–90

Ranius T (2001) Constancy and asynchrony of Osmoderma eremita

populations in tree hollows. Oecologia 126:208–215

Rink M, Sinsch U (2007) Radio-telemetric monitoring of dispersing

stag beetles: implications for conservation. J Zool (London)

272:235–243

Rink M, Sinsch U (2011) Warm summers negatively affect duration

of activity period and condition of adult stag beetles (Lucanus

cervus). Insect Conserv Diver 4:15–22

Rowe L, Ludwig D (1991) Size and timing of metamorphosis in

complex life histories, time constraints and variation. Ecology

72:413–427

Shaffer ML (1981) Minimum population size for species conserva-

tion. Bioscience 31:131–134

Shibata E (1986) Adult populations of the sugi bark borer, Semanotus

japonicus Lacordaire (Coleoptera: Cerambycidae), in Japanese

cedar stands: population parameters, dispersal, and spatial

distribution. Res Popul Ecol (Kyoto) 28:253–266

Smith MN (2003) National Stag Beetle Survey 2002. People’s Trust

for Endangered Species, London

Sodhi NS, Ehrlich PR (2010) Conservation biology for all. Oxford

University Press, New York

Southwood TRE (1978) Ecological methods with particular reference

to the study of insect populations. Chapman and Hall, London

Speight MCD (1989) Saproxylic invertebrates and their conservation.

Council of Europe, Strasbourg

Stoks R (2001) Male-biased sex ratios in mature damselfly popula-

tions: real or artefact? Ecol Entomol 26:181–187

Sutherland WJ (2006) Ecological census techniques. Cambridge

University Press, New York

Svensson GP, Larsson MC (2008) Enantiomeric specificity in a

pheromone-kairomone system of two threatened saproxylic

beetles, Osmoderma eremita and Elater ferrugineus. J Chem

Ecol 34:189–197

Svensson GP, Sahlin U, Brage B, Larsson MC (2011) Should I stay or

should I go? Modelling dispersal distances in a threatened

saproxylic beetle, Osmoderma eremita, based on pheromone

capture and radio telemetry. Biodivers Conserv 20:2883–2902

Thomaes A, Kervyn T, Maes D (2008) Applying species distribution

modelling for the conservation of the threatened saproxylic Stag

Beetle (Lucanus cervus). Biol Conserv 141:1400–1410

Tikkamaki T, Komonen T (2011) Estimating population character-

istics of two saproxylic beetles: a mark-recapture approach. J Ins

Conserv 15:401–408

Vrezec A, Kapla A (2007) Kvantitativno vzorcenje hroscev (Cole-

optera) v Sloveniji: referencna studija [Quantitative beetle

(Coleoptera) sampling in Slovenia: the reference study]. Acta

Entomol Sloven 15(2):131–160

Vrezec A, Kapla A, Grobelnik V, Govedic M (2006) Analiza

razsirjenosti in ocena velikosti populacije rogaca (Lucanus

cervus) s predlogom conacije Natura 2000 obmocja Goricko

(SI3000221). Nacionalni institut za biologijo, Ljubljana,

Slovenia

Vrezec A, Polak S, Kapla A, Pirnat A, Grobelnik V, Salamun A

(2007) Monitoring populacij izbranih ciljnih vrst hroscev –

Carabus variolosus, Leptodirus hochenwartii, Lucanus cervus in

Morinus funereus, Rosalia alpina. Nacionalni institut za biolog-

ijo, Ljubljana, Slovenia

Werren JH (1993) The Natural History of Inbreeding and Outbreed-

ing: Theoretical and Empirical Perspectives. University of

Chicago Press, Chicago, Illinois

White GC, Burnham KP (1999) Program MARK: survival estimation

from populations of marked animals. Bird Study 46:120–139

J Insect Conserv

123

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