Table Of ContentJournaloftheLepidopterists'Society
53(4),1999,138-141
METHOD OF HANDLINGAFFECTS POST-CAPTURE ENCOUNTER PROBABILITIES IN
MALE HYPOLIMNAS BOLINA (NYMPHALIDAE)
(L.)
Darrell Kemp
J.
SchoolofTropicalBiology,JamesCookUniversity,RO. Box6811Cairns,Queensland,4870,AUSTRALIA
AND
Myron P. Zalucki
DepartmentofZoologyandEntomology,TheUniversityofQueensland,StLucia,Queensland,4072,AUSTRALIA
ABSTRACT. Mark-recapturestudiesofbutterflypopulationsareoftenplaguedbylowrecapturerates,whichmakepopulationestimation
problematic. Onereasonforlowrecapturesisthatthehandlingprocessofcapture,markingandreleasecontributestolowandunequalcatch-
abilityofmarkedindividuals. Herewereporttheresultsofanexperimentconductedtoevaluatethehypothesisthatcoolingindividualspriorto
release minimizes handling effects. The post-capture difference in site fidelity of territorial male Hypolimnas bolina (L.) (Lepidoptera:
Nymphalidae)wascomparedamongthreegroups:(1)maleshandlednormally,(2)maleschilledpriortorelease,and(3)uncaughtcontrols.Un-
chilled malesshowedsignificantlyreducedsitefidelitycomparedtobothcontrol andchilledbutterflies. Furthermore,chilledbutterfliesre-
sumedactivityaftercaptureinamannersimilartouncaughtcontrols.Theseresultsindicatethatchillinghasthepotentialtominimizethead-
verse effects of handling on subsequent butterfly catchability. Since 'equal catchability' ofcaught and uncaught individuals is a critical
assumptionofmark-release-recaptureprograms,thismethodhasthepotentialtogreatlyincreasetheaccuracyofsubsequentpopulationesti-
mates.Onthisbasis,inpopulationstudiesonbutterflies,theprecisemethodofhandlingmayproveamoremeaningfulconsiderationthanthe
questionofwhetherornottohandle.
Additionalkeywords: catchability,mark-release-recapture,censusing,populationestimation.
Mark-recapture methods represent apowerful tool Inrecenttimes, manyworkershavetakentocooling
for the estimation of animal population parameters, individuals before their release (e.g., Bull et al. 1985,
especially those ofinvertebrates (Seber 1973, South- Zalucki & Kitching 1985, Suzuki & Zalucki 1986, Ru-
wood 1978, Begon 1979). These methodologies have towski 1992, Zalucki 1993,Wickman &Jansson 1997).
often been applied to the study ofbutterfly popula- This technique stems from theideathatincreasedim-
tions; however, on manyoccasions, such programs are mobilization ofindividuals immediatelyprior to their
plagued by low recapture rates, sometimes in the or- release helps to reduce their subsequent degree of
derof1 to 10% (Brussard&Ehrlich 1970, Urquhartet 'panic' (Wickman & Jansson 1997). In this way, indi-
al. 1970, Cooketal. 1971, Urquhart& Urquhart 1976, viduals aresupposedlymorelikelytoremainintheim-
Wattetal. 1977,Cullenwardetal. 1979).Thismakesthe mediate study area and behave normally, rather than
estimationofpopulationsizeandrelatedmeasuresprob- disperse andavoidfurthercapture (asfoundbyLeder-
lematic (Rosenberg et al. 1995), and researchers must house 1982). The use of this technique, however, is
often resorttolesspowerful methods, such as transect- based on mostly anecdotal information, and little, if
based surveys to census theirpopulations (e.g., Pollard any, published research has been conducted to evalu-
1977, Eberhardt 1978,Thomas 1983, Dent 1997). ate its merit.
One ofthe manypotential causes oflow recapture The aim ofthis paper is to evaluate the hypothesis
rates in the Lepidoptera is that the actual process of that cooling individuals prior to release may increase
capture and handling may affect the behaviour of their subsequent catchability relative to individuals
markedindividuals, reducingtheirchanceofbeingre- handled in the normal manner. This hypothesis is in-
captured (Gall 1984). This effectwould contribute to vestigated using territorial mate-locating males ofthe
lowcatchabilityinmarkedindividuals, andleadto sig- nymphalidspecies Hypolimnasbolina (L.).
nificant bias in subsequent population estimates (Gall
Materials And Methods
1984, Rosenberg et al. 1995). Although crucial to the
application of mark-recapture methods, few authors MaleH. bolina inresidentterritorieswerecensused
attempttovalidatethe assumptionof'equalcatchabil- along a 1020 m transect (Rutowski 1992) located on
ity' (Gall 1984). Severalattemptstoassaytheeffectsof campus atJames Cook Universityin Townsville, Aus-
capture in butterflies have indicated that the capture tralia (19°15'S, 146°45'E). Samplingwas conductedin
and handling process may have strongly negative ef- two rounds in 1998; from 9-12 February and 16-19
fects on subsequent catchability (Singer & Wedlake April, and once in 1999; from 22-25 February 1999.
1981, Lederhouse 1982, Morton 1984). On each sample round, transects were censused
Volume 53, Number4 139
countopportunities (i.e. thenumberoftimeshis terri-
tory was passed during transect censuses). Since the
ratioofbefore: after-markingcountsineachtreatment
group was homogenous between sampling rounds
(Chi-squared homogeneity test on before- and after-
counts across thethree rounds: %2 < 2.79, p > 0.24for
each group), data were pooled across all rounds. Ini-
tially, pre- andpost-markingroundcountprobabilities
werecomparedforcontrolgroupbutterflies only. This
was done to check that the activity ofuntreated but-
Control Chilled Unchilled terflies was homogenous and that no other factor, for
instance weather, affected the probabilityofcounting
Fig. 1. Theaverage (± SE) differenceintheprobabilityofen-
countering a male H. bolina between pre- and post-capture cen- butterflies between censuses. Mean differences (pre-
suses, as a function ofwhich treatment group hewas assignedto. andpostmarkinground)incountprobabilitiesbetween
Control males were not caught, chilled males were caught and butterflies of each treatment group were then com-
cooled before release, and unchilled males were caught but not
chilled. pared using a one-way analysis ofvariance (ANOVA).
Three comparisons were planned prior to analysis;
these were (1) between chilled and unchilled butter-
hourly for the first two days to identify individuals of flies, (2) between chilled and control group butterflies,
high territory site fidelity (for census techniques see and (3) between unchilled and control group butter-
Pollard 1977). Notes onsizeandwingwearweretaken flies. These contrastswere evaluatedusingleast signifi-
to allow reliable identification ofthese individuals in cant difference (LSD) testforplanned, non-orthogonal
subsequent censuses (Rutowski 1992). At 1000 h on comparisons (Sokal & Rohlf1995). Priorto conducting
the third day (termed the marking round), each resi- analyses, datasetsweretransformedusingthe angular
dentwas randomlyassignedto one ofthree treatment transformation, andKolmogorov-Smirnovgoodnessof
groups. 'Unchilled' males were captured at their site, fittestswereusedtoconfirmthatthetransformeddata
marked with an identification number on both hind- were normally distributed (Kolmogorov-Smirnov d <
wingundersides, andreleasedimmediately(totalhan- 0.24, p > 0.20 for all groups). Levene tests were used
dling time of 40-50 seconds). 'Chilled' males were to check homoscedasticity among ANOVA groups;
similarly captured and marked, but were held for a these were non-significant in all cases (p > 0.175),
further 210 seconds in a paper envelope placed on a which confirmed that datawere homoscedastic. Two-
blockoficewrappedin newspaper (Wickman &Jans- tailed probabilities were used, and sample means
son 1997), then released directlyback to their perch. throughoutthis paperare given ± 1 standarderror.
Notes were taken on the immediate behavior ofindi-
Results
viduals in these two treatments upon release. Butter-
fliesofthethirdgroup, designatedascontrol,werenot Atotalof30primaryterritoryresidentswereidenti-
caught. Hourlytransects were then conducted forthe fied during the three sampling occasions, and these
remainder ofthe third day and the next dayto deter- were randomlydistributed amongst treatments as fol-
mine the behavior ofmales in all three groups. Cen- lows: 11 chilled, 11 unchilled, andeightcontrol. Ofthe
suses were conducted no sooner than 0900 h and no total 226 count opportunities before the marking
laterthan 1500h, andonlyinthepresence ofsunshine round, 191 counts were registered, and primary resi-
before andduringtheentiretransect. Thiswas doneto dents exhibited a mean site fidelity of 0.87 ± 0.02
ensure thatindividualswere censused onlyattimes of (eachbeingpresenton approximately87% ofallcount
maximum site fidelity. Duringthe course ofeachtran- opportunities). Mean pre-marking site fidelitydid not
sect, individualmaleswere deemedre-countedifthey differ significantly among the three butterfly groups
were within 20 meters of their designated territory, (control, chilled, unchilled; ANOVA on angular-trans-
and activelyengaged in defense ofthat site. No effort formed data, F227= 0.15, p = 0.86). In addition, the
was made to search for individuals that were not im- mean site fidelity ofcontrol group butterflies was not
mediately obvious at their sites following marking, significantlydifferent between pre- and post-marking
hence the observation technique was kept similarbe- censuses (pairedt-test on angular-transformed data, t
fore andaftermarking. = 0.63,df=7,p = 0.55).
Anindexofsite fidelitywas calculatedforeach male Post-marking censuses revealed that four marked
by dividing his total counts by his total number of individuals (one chilled and three unchilled) had de-
140 Journalofthe Lepidopterists' Society
serted their territories. All other males were counted ingbutterflies priorto theirrelease, andit mustbe as-
at least once defending theirpre-designated territory sumed that butterflies were simply released immedi-
area. The mean difference between pre- and post- ately following marking. The experiment conducted
marking round fidelity varied significantly among hereonH bolina corroboratesthe findingthatbutter-
.
treatment groups (ANOVA on angular-transformed flieshandledinthis mannermaybelesslikelytobere-
data, F = 3.97, p < 0.05; Fig. 1). Fidelity was re- captured, butthatthis adverse handlingeffect maybe
2 27
duced to a varying degree in all groups following the mediatedbyachillingtreatmentpriorto release.
marking round. The reduction in site fidelity of un- Oneconcernwithcapturingandmarkingbutterflies
chilledbutterflieswas significantlygreaterthanthatof isthatindividualswillsufferfrom anincreasedlevelof
eithercontrolorchilledgroupbutterflies (LSDtestfor predationowingtothewingmarkandsubsequentloss
plannedcomparisons,p < 0.05). Thesignificantdiffer- ofcrypsis or aposematism (Gall 1984, Reynolds et al.
ence between the two captured treatment groups 1997). Ifpresent, suchaneffectisoften difficulttodis-
demonstratedaneffectduetothe methodofhandling tinguish from any potential effects arising from cap-
individual males before their release. Furthermore, ture and handling. Fortunately, in this study, the con-
thechangeinfidelityamongchilledbutterflies didnot trasting results between treatment groups allowedthe
differ significantly from that shown by control group separation of specific marking effects. Since both
butterflies (LSD test, p = 0.85). Hence, relative toun- treatment groups were given similar marks, chilled
caught controls, the process ofcapture and marking males provided an adequate control forthe effects of
hadnoappreciableeffectonthe subsequentterritorial wing marks in the unchilled group. That onlythe un-
fidelity ofbutterflies that were chilled prior to their chilled group ofbutterflies were less likely to be re-
release. counted than controls clearlysuggests that, at least in
Captured and marked butterflies in each treatment the short term, these were affected bythe method of
group showed clear behavioral differences following handling and not by the marks placed upon their
theirrelease. Whileallchilledmales remainedperched wings. A similar conclusion was reached by Morton
on the substrate where theywere placed, non-chilled (1984),whofoundthatcoloredwingmarksdidnotsig-
males either resumed active territory defense (2 nificantly affect recapture ofthe highlycryptic wood-
males), roosted on the underside of shaded foliage landbutterflyMelanargiagalathea (L.). Thelimitation
nearthesite (2males),orflewquicklyoutofthearea(7 with the current experiment, however, is that post-
males). Hence,whileallchilledbutterfliesremainedin markingsite fidelitywas onlymeasuredforaperiodof
the vicinity oftheir territory (i.e., less than 20 meters two days. On this basis, the presence ofa longerterm
away) in the first instance, only 4 (36.4%) ofthe 11 effect due to wing marks in H. bolina cannotbe com-
non-chilledbutterflies did so. pletelydiscounted.
The question ofwhy captured butterflies may be
Discussion
less likelyto be resighted is not specifically addressed
Althoughbasedon relativelysmall sample sizes, the bythis study,butsomeinsightis affordedbycasualbe-
results ofthis experimentclearlysupportthehypothe- havioral observations made on released individuals.
sis that cooling may reduce capture effects and in- Clear differences in behavior were evident between
creasepost-handlingcatchabilityofterritorial male H. treatment groups, and this resulted in more unchilled
bolina. Not only did the process ofchilling affect the butterflies leaving their immediate area ofcapture in
probability of resighting captured males, but chilled the shortterm. This differencealonemayberesponsi-
males also resumedactivityinamannersimilartothat ble for differences in encounter probabilities ofun-
ofbutterfliesthatwerenevercaught. This resultissig- chilledandchilledindividuals, especiallyinthecaseof
nificant, since itshowsthatchillingmaynotsimplyre- a site-tenacious butterfly such as male H. bolina
duce or 'manage' the adverse effect ofhandling, but (Rutowski 1992). In unchilledH. bolina, the decision
that this process has the potential to actually nullify to leave the territory is more likely to be made as a
short-term effects ofcapture. To ourknowledge, this consequence ofimmediate 'panic' upon release. This
has notbeen demonstrated previouslyfor anybutter- behaviorappearssimilartothedefensiveorevasivere-
flyspecies. sponse of butterflies to failed predatory attacks, or
These results contrast with the generally negative failed capture attempts. Chilled butterflies, however,
effects ofhandling ofbutterflies obtainedin previous remain in their territory area for quite some time
studies, forexample SingerandWedlake (1981), Leder- whilst warming up, and therefore any active decision
house (1982), and Morton (1984). In these studies, to abandonthe site mustbe made at some later stage.
however, no reference is given to anymethodofchill- On average, the difference between groups after
Volume 53,"Number4 141
marking is that unchilled butterflies must decide dae),withacomparisonofdifferentnumericalmethodsthates-
whether to return to their former territory, and the timatepopulationsize. Biol.Cons.28:139-154.
Lederhouse, R. C. 1982. Factors affecting equal catchability in
chilled butterflies must decide whether to leave. If two swallowtail butterflies, Papilio pohjxenes and P.glaucus.
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