Survival rates, site fidelity and homing ability in territorial Calopteryx haemorrhoidalis (Vander Linden) (Zygoptera: Calopterygidae)

14 Pages·2002·1.9 MB·English

by  Beukema, J J

Odonatologica31(1):9-22 March I.2002
Survival rates, site fidelity and
homingability in territorial Calopteryx
haemorrhoidalis(Vander Linden)
(Zygoptera: Calopterygidae)
J.J.Beukema
Netherlands Institute forSea Research, POBox 59, 1790AB DenBurg,The Netherlands
e-mail:[email protected]
ReceivedFebruary 19,2001/RevisedandAcceptedJune6,2001
InasmallisolatedpopulationalongasmallstreaminNESpain,ahighproportionof
the adultspresentwereindividuallymarked. Duringsubsequentdays,their locations
wereassessed bytwice-dailysurveysalongthe entire lengthofthe stream.Meandaily
survivalrates inmature<J 3 and 2 2 and pre-reproductive 36 weresimilar,94%.
Onlyduringthe firstdayaftermarkingweresurvival ratessignificantlylower(viz. 77
to 84% in the various groups). High proportions(around90%) ofmature 3 3 were
foundtoreturn tothesame(territory)site every morningoncetheyhadoccupiedthat
site for2ormoredays.Sitefidelitywaslow inpre-reproductive33andintermediate
inmature 22. In adisplacementexperiment,67 territorial 33weretransferredone
byonetodistantlocations(80to240malongthestream).Halfofthemreturnedtotheir
originalterritory,usuallyonthesameday.
INTRODUCTION
Inmanyspecies ofOdonata,including theCalopterygidae, mature malesdefenda
territory against conspecific malesandguard conspecific femalesovipositing within
it.Insomespecies, territorialmaleshavebeenobservedtousethesamelocationday
after day as aterritory, thus showing strong and persistent site fidelity. CORBET
(1999)lists28species inwhichmaleshavebeenobservedforperiods of 10or more
days atthesameterritorysite. ThislistincludesC. virgowithamaximumof40 days
(KLOTZLI, 1971), C. haemorrhoidaliswith 19 days (HEYMER, 1973), and C.
splendens with 13 days (ZAHNER, 1960),including interruptions forshortperiods,
e.g. dueto adverse weatherconditions.Theserecords clearlyshow theexistenceof
long-term attachmentto specific territorysites. However, they usually lackfurther
information,such as frequency ofshiftstoother sitesanddependence onage.Inthe
10 J.J. Beukema
non-territorialfemalesandimmaturemales, lowersitefidelity is expected, but any
attempt to quantify the expected differencewithreproductive males appears tobe
lacking. Moreover,dataonsitefidelityshouldbeincorporated intoastudyofpopulation
dynamics,becausethechanceofencountering anindividualonsubsequent days atthe
same locationis affectedby its dailysurvival rate andestimates of durationofsite
fidelity shouldbecompared tothoseoflongevity.Therefore,estimatesonsurvival are
indispensable inastudy onsitefidelity.
Ifmalesleavetheirterritoryintheevening tospend thenightaway fromthewater
(ase.g.C. haemorrhoidalismalesdo),multi-daysitefidelity shouldinvolveanability
toreturn totheright spotandrecognize it; i.e.territorialmalesshould beabletouse
somememoryofthecharacteristicsoftheirterritoryandofitssurroundings toefficiently
return toitonsubsequent days.
Inthepresentpaper,Idescriberesultsofmarking experiments inasmallpopulation
of Calopteryx haemorrhoidalis(Vander Linden) living along a small stream in
northeasternSpain. Severalhundredadultmalesweremarkedindividually. By daily
surveys oftheentirearea occupied by the population, the presence along thestream
and theexactlocationofmarkedindividualswas assessed during subsequent days.
Because high proportions ofthemarkedindividualswerefrequently resighted, these
observations allowednot only an estimateoftotal local daily survival rates (the
proportionofanimalsthatdidnotdienordisperse fromthestream sectionsurveyed),
butalsoofchancestoresightthematthesamesite.Bydisplacing territorialmalesand
frequently watching their territoryand adjacent areas, theprobability andspeed of
theirreturn wereestimated.
METHODS
Thepopulationsstudiedlivedalongasmallstreaminthefoothillsoftheeastern PyreneesinSpain,a
fewkmNorthofthe villageofMontagut,betweenthetowns ofBesalutand OlotinGironaprovince.The
streamiscalledTorrente delEstanyoland itslocation isindicated onamapby WASSCHER (1996).The
sectionofthestreamthatwasregularlysurveyedextendedfromacascadeclosetothesourcetooneabout
650m downstream, where the streamemptiesitself into abroader valley. As thisrocky valleylacks
almostanyvegetationanddriesupinthecourseofmostsummers,itisunsuitableforCalopteryxterritories.
Therefore,the studiedadultpopulationappears tobe isolatedfromsuitableneighbouringhabitats,since
theseweremorethan1km awayandseparatedbydrywoodlandandrocks.
In summer,the widthofthestreamlocallyvariesbetween0.3and5.0m,itsdepthbetween0.1and1.0
m,butafterheavyrainthe water level maybe up to 1m higherasjudgedfromdebriswashed upin the
shrubs.Thebottomischalkywithnumerousridges,slowingdownthecurrentspeedandcreatingnumerous
pools.Theborders aremostlywoodedwith talltrees andshrubsalongmost ofthe650-m stretch,but
sunnyspots arenumerousonandalongthewater.However,mostofthetotal watersurfaceisinthe shade
morethanhalf ofthe day,leavingonlylimitedsuitableareasfor territories. Watertemperatures in the
June-Augustperiodgenerallyrangedfrom14°Catthesourceandindeeppools to17°Catshallowstretches
downstream,butoccasionallyrosetoover20°Catthelowerreaches.Airtemperaturesweremorevariable
androseonsunnysummerdaystovaluesbetween20and30°C. However,onabout 10%ofthedaysthe
skyremainedovercast during(almost)theentiredayandfew(ifany) Calopteryxappearednearthewater
onsuchdays.
PopulationbiologyofCalopleryxhaemorrhoidalis 11
Thepopulationsweresurveyed during12to20 successive days(interruptedonlyby afewdayswith
inclementweather)ineach of7 years, aslisted inTable I.Highestnumbers ofCalopteryxwerepresent
between 11a.m.and5p.m.(asalsoobserved alongthesamestreamby WASSCHER, 1996). On days
with suitableweather,allpotentialterritorysites wereinspectedatleasttwice perday.The surveytrack
followed the stream,nearlyentirelyby wading.As many aspossiblemales (andalso several females)
werecaughtbygentlenettingandmarkedby auniquecombinationofwhiteand/orredpaintspots onthe
outersidesofthewings(orontheuppersideofthebody).Whitecorrectionfluidandrednailvarnishwere
applied.Numbers ofmarked individuals rangedfrom 14to 176 inthe 7years, totaling559 (Tab.I).
Markingplace,sexandaroughestimateofagewerenoted. Anindividual wasnotedasimmatureifitdid
notyetshowthefullmaturewingcoloration.After aboutoneminute(toallowthepaintto dry),amarked
individual wasreleasedatthesameplace,whereitusuallyflewupintothetrees.Locationsatmarkingand
at all subsequentencounters (calledresightings)werenoted with aprecision ofonetoafew meters,
relativetocharacteristictrees andotherlandmarks indicated onamap.Themarkswerelargeenoughto
allowrecognitionfromadistanceofseveralm.
Toinvestigatetheir homingability, 67 marked maleswerecaughtwithin their territory,moved in a
closednettoalocation atthe streambetween80and240maway,andreleased within about 10min after
catching.These maleshadbeen marked severaldaysbeforeandresightedatthesamesiteforatleast4
daystoassessthattheywereownersofafixedterritory.Duringsubsequentsurveys (thefirstoneusually
onthetransferday),theirpositionalongthestreamwasrecordedasfrequentlyasfeasible(usuallytwice
daily).
Thex2 testwasusedthroughoutthepaper toevaluatestatisticalsignificanceofobserveddifferencesin
numbers.
DAILYSURVIVAL
In all years, most of the marked individuals were seenagain during subsequent
surveys. Theresighting percentages were generally slightly higher inmalesthan in
females,butthedifferencewas not significant(0.05<p< 0.1),whereasthedifference
betweenmatureandimmatureindividualswas farfromsignificant (Tab.I).
Table I
Numbers ofprereproductive(immature)andmaturemalesandfemalesofCalopteryxhaemorrhoidalis
marked and percentages (%)seenagainon atleast onesubsequentdayih each ofseven observation
periods. — [Afterafewdaysofmarkingeffort,thenumbers ofmarked individuals includednearlyall
trulyterritorialmalesandmostoftheother maturemales,butonlylowproportionsofthefemalesand
immature individuals]
Year Period Numbermarked Percentageresighted
males females males females
imm, mature imm. mature imm. mature imm. mature
1991 12/VII-23/VII 0 36 0 0 81
1992 13/VII-27/VII 0 32 0 4 75 25
1993 14/VII-02/VIII 4 142 0 30 50 85 83
1994 28/VI-15/VII 1 9 0 8 100 100 100
1996 19/VI-07/VII 3 102 0 27 100 89 78
1997 06/VI-25/VI 26 83 10 28 77 83 70 79
1998 12/VI-22/VI 1 7 0 6 100 71 50
Totals 35 411 10 103 77 84 70 78
12 J.J.Beukema
Thedailyrecordsofthemarkedindividualswereusedtoassess minimalnumbers
andpercentagesofindividualsstill aliveon successive daysaftermarking foruse
incalculationsofdaily survivalrates andmean longevity. Effectsofoverlooking by
theobserverduringsurveys orabsenceofthe damselflyalongthe surveytrackdueto
adverse weather conditionscould partly be nullifiedby considering individuals
encounteredona certainday to havebeen aliveon all foregoing days betweenthe
markingdayandthe dayofobservation. Nevertheless,itshouldbekept inmindthat
thesurvivalestimatesareboundtobeunderestimates,becausetheobserverwillcertainly
haveoverlookedsomeindividualsbeforethe dayoftheirdeath.
Thepercentagesofmarkedindividualsstillalivegradually declinedataregularrate
during thefirstten days aftermarking when numberswere stillhighand estimates
wererelativelyprecise (Fig. la).Thebest fittinglinesthrough thepointsshowninthis
Figure mn slightly curvilinear, becoming Unearon alogarithmic plot starting from
day-1.Thispointstoaconstantdailyrateofsurvivalstarting from1 dayaftermarking.
Theselinesrunalmostparallel inmalesandfemales,corresponding toadailysurvival
rate of94%betweendays-1 and-10 inboth sexes (Fig. la). Neitherdidthesurvival
ratesofimmatureandmaturemalesdiffer(Fig. 1b).Lownumbersofmarkedimmature
femalesdidnotpermit aseparatesurvivalestimateforthis group.
The aboveestimateof daily survival of94% did not apply tothe first day after
marking (day-0 to day-1). On this initialday, survival was substantially lowerthan
94% in all groups,viz. 84% in mature males, 78% inmature females and 77% in
immaturemales.Differences betweensurvivalrates forthefirstandthesecond day
Fig. 1.Calopteryxhaemorrhoidalis, minimalpercentages ofgroupsofmarkeddamselflies stillaliveon
successive daysafter the markingat day-0:(a) summedobservations (addeddataofall 7 periodsof
observation)on446 marked males (•) and 113females (o); — (b) observations made in 1997 on83
individuals markedasmature(•) and 26asimmature(o)males.
PopulationbiologyofCalopteryxhaemorrhoidalis 13
aftermarking werestatistically significantbothin males(p<0.01, n=446 and373)
and infemales (p <0.01, n= 113 and 87). Apparently, therewere extra losses of
between ~ 10% and 17% immediately aftermarking. In other words, handling for
markingroughly tripledthenormaldailydisappearancerateof6%.Thepresentmethods
donotallowmaking adistinctionbetweenmortality,emigration,andadditionalmortality
brought aboutby beinghandled.
SITEFIDELITY
During theevening, nightandearly morning, C. haemorrhoidaliswerenotpresent
alongthesurveytrack. They wereprobablyroosting at communalroosts highabove
thewater surface,invisibleinthecrownsofthetrees.They were seento descendinthe
course ofthe morning,butnumberand locationof theroosts could not beassessed.
Reproductive malestook a territory generally between 10 a.m. and noon. Marked
individualswere usually resighted atthe samesite (often even on the sameperch)
wherethey hadbeenseenontheprevious day.Alongtheregularly surveyed stretchof
thestream,about60sites weresuitableforaterritory(i.e. theseplaces werefoundto
be frequently occupied by a
territorialmale). I definedand
TableII
namedsuch suitablesites witha Site fidelity(%)inmaturefemales andinvarious adult life
diameter of generally several
stages of males of Calopteryx haemorrhoidalis. —
meters. These sites were larger [N = number of observations. Statistically significant
than the small areas (afew m2 differencesbetweentwo figuresare indicatedby symbols
,
comparealso the even smaller placedinbetween the comparedfiguresonly asfarasthe
0.5to 1.5m2given byCORDO- fcicoamnpt,ar*is=onpis<c0o.n0s5i,de*r*ed=topb<e0m.0e1a,nainndgfu**l:*0==pno<n-0s.i0g0ni1-]
BA-AGUILAR,2000)actually
defendedatanytime.Thiswas a Sex and Dataof:
consequence of the males’ condition 1997only allother years
tendency to change his perch % (N) % (N)
withinthesesitesaccording tothe
Females:
sunlit parts, which could shift all mature 53 (112) 60 (182)
severalminthecourseoftheday. ** ***
Therefore, it was inevitableto
Males:
recordanindividualas being at
all mature 69 (296)-| 78(1682)
thesame site if it was present **￿
within about 5 m from the imm.coloured 40 (40)
location of the preceding O
J
observation. rec.mature 47 (32)
***
To quantify site fidelity, I
territorial >4d 92 (127) 95 (339)
expressed it as a percentageof * ***
allresights ofan individualthat
were atthe same site (within5 last daysterrit. 77 (13) 60 (15)
14 J.J.Beukema
m) asthelast observationofthat individual.The lastobservationwas usually onthe
previous day,butmayhavebeenmorethanone dayearlier,e.g.ifweatherwas badon
theintervening day. TableIIshows asummary oftheobservedresight percentages,
separatelyfor 1997-only andforallotheryearstogether (1997was theonlyyearwith
a high numberof immatureindividuals atmarking, allowing separateestimates for
groupsofmalesof differentknownageandmaturitystate).
As expected, mature females showed significantly lowersite fidelity thanmature
males(Tab.II: toprows). Amongthe males,sitefidelity was dependent ontheirlife
stage. Those withclearly immature colours andindividualsthat hadonly recently
(< 3 days before) attained mature coloration(“rec. mature” in Tab. II) showed
significantly lower site fidelity
than fully mature males. Site
fidelitywasparticularlyhigh (well
above90%) inmature malesthat
occupied a certain territory al-
ready for several (> 4) days.
However, it declined during the
lasttwodaysoftheirlife, viz.toa
significantly lowerpercentageof
60-77% in males that had
occupied aterritoryfor >4 days
during the period immediately
preceding the last two days they
wereresighted (Tab.II).Itwillbe
meaningful that the few obser-
vationsofaterritorialmalelosing
aterritorialfight,werejustbefore
theendoftheresighting period in
thatmale.
Site fidelity percentages were
positivelyrelatedtothenumberof
days an individual had already
Fig. 2. Calopteryxhaemorrhoidalis,percentages ofindi- beenpresent ata certainsite.IfI
vidualsthatwereresightedatthesamesite(i.e.within- 5m had seenareproductive maleata
oftheformersite)afterhavingbeenseenthereon 1,2,3...8
ormoreprecedingdays(withoutinterruptionsofsightingsat certain siteon two or moredays
othersites).Dataonthreegroupspresentedseparately:mature (without intervening days at
6 (°= 1997, 0=1996,*= 1993,□=summeddataof1991, another site), thechance thatthe
1992, 1994, and 1998;totalsofall7 years indicated by an next resighting wouldbe atthe
uninterruptedline); —mature9(+anddashedline;totalsof samesite(andnotelsewhere)was
all years); and - immature individuals (xand dottedline;
totalsofall years). Apercentage is shownonly if >10 ca90%andevenhigher (ca95%)
observationswereavailable (seenumberofobservationsgiven iftheindividualhadkeptthesame
atthetopoftheFigure). territory for more days (Fig. 2:
PopulationbiologyofCalopteryxhaemorrhoidalis 15
opencircles). Thesehigh site fidelitypercentagesaftertwoormore days atthesame
siteweresignificantly(p <0.001) higher thanthepercentagesofca60%foundaftera
preceding stay atthatsiteofonly one day.Notethatsuch one-day-only observations
constituteda heterogeneous group,since thisgroupincludednotonly individualsthat
hadreally stayed there foronly one daybut alsoindividualsthat couldhave been
presenttherealsoonearlierdaysbutwerenotyetmarkedorobserved.Thismeansthat
sitefidelity must havebeen lowerthan ca60%in mature malesthathadbeen ata
certainlocationforonlyexactly one day.Sitefidelity inrecently maturedmales(those
notyettruly territorial)amountedto47% (Tab.II). Asa consequenceoftherelatively
low site fidelity in young(though looking fully mature-coloured) males, malesite
fidelity tended toincrease inthe course ofthe season (June-August), reflecting the
increaseoftheproportion offullyreproductive males.
In immaturemales, thepercentagesoccurring atthesamelocationas onprevious
days were not only lowerthan inmature males. Another differencewas thatthese
percentagesdidnot showanincreasewithnumbersofdaysthey hadbeenseen atthis
site(Fig.2:thexpoints).Though immatureindividualsdidnotshowaclearattachment
toasite, almosthalfoftheresightings onlaterdays wereatroughly thesamelocation,
i.e.withinabout5 m,butnotatspecificperchesandgenerallyseveralmawayfromthe
watersurface(as opposed tofullyreproductive males,whowereoftenobservedatthe
sameperchclosetothewatersurfacedayafterday).Generally,thereproductive males
wereresighted every day (weatherpermitting), whereasoften several days elapsed
betweensuccessiveresightingsofimmatureindividuals.
Inmaturefemales,sitefidelitypercentageswere mostlylow(ca50%),butincreased
tolevelssimilartothoseofreproductive malesonceanindividualfemalehadbeenat
thesamesiteforthreeormoredays(seeFig. 2,+pointsanddashedline; thedifferences
weresignificantbetween 1 andeither2,3,or4days,andbetween2and4 days).The
differencesinsitefidelitybetweenmaturemalesandfemales(uninterruptedanddashed
lineinFig. 2,respectively) weresignificant(p <0.01)after1 and2 days,butnotafter
3or4days. Thehighsitefidelityvaluesinmature femalesafterstays of3ormoredays
atthesamesite wereduetoalownumberofindividualsthatreturnedtothesamesite
dayafter day. Mostfemaleswere resighted less frequently and mostly atsites that
differedfromdayto day(observations ofthesefemalesare includedintherelatively
large 1-daygroupinFig. 2, cf.numbersofobservations).
A high site fidelity of about90%, as observed in territorialmales, means that
individualsusuallysticktothesamesiteforseveral days insuccession. Long seriesof
10ormore dayswerenot atallrare (though such serieswerefrequentlyinterruptedby
oneor two days ifweatherwas bad). Such long series were observed in about50
males.
Thelongest periodaterritorialmalewas seen atthesamelocationwas 20 days,but
thiswillbeanunderestimate, since thelongest survey period lastedonly 20 days (in
1997, seeTab. I).
16 J.J. Beukema
TableIII
Numbers ofterritorial males ofCalopteryxhaemorrhoidalis transferred toanothersite atthe stream,
and eitherneverseenalive onsubsequent days,orresighted attheiroriginalterritory site,at therelease
site,orelsewhere (either betweentherelease and the territory site orbeyondthis stretchofthe stream)
Year Transferred Never Location offirstresightaftertransfer
number resighted Territory Release Between Beyond
site area
1992 11 2 6 3 0 0
1993 35 6 15 6 5 3
1996 21 2 9 4 4 2
Totals 67 10 30 13 9 5
HOMING ABILITY
By farmost(57) ofthe67transferred maleswereresighted atsubsequent surveys
along thestream. Theloss of10 individualsappearstobesomewhatinexcess ofthe
normaldailymortalityof6%, buttheextrahandling (catchingandmoving) mayhave
enhanced the disappearance rate as observed immediately afterinitialmarking (see
above).
Abouthalf(30) ofthe57survivors amongthetransferredmaleswereencountered
afterwards atthe site of theiroriginal territory (Tab. IB). Quick returns, already
completed on the dayofthetransfer, were observedin 19males.Theproportion of
quickreturns wascertainlyunderestimated,since someofthemoveswouldhavetaken
place afterthelastsurvey ofthe day.
Nearly halfofthe27individualsthatdidnot returntotheirterritorywereobserved
tostay atthereleasesite.Many oftheotherswereresighted somewherebetweenthe
releaseandtheoriginalterritorysite,but5 maleshadmovedintothe“wrong” direction
(Tab. III). Many moremaleshad movedintothe“right”thanthe “wrong” direction,
viz. 30+9= 39versus 5. Thus,a hypothesis thattheirreturn flightresultedinanet
movementintoarandomdirectioncanberejected (p<0.001,signtestwithn=44).
Resultsofupstreamtransfersdidnotdifferfromdownstreammoves: returns tothe
original territory were 16outof36 upstreammoves and 14out of 31 downstream
moves.
Thedistanceofthemovesmayhaveaffectedthe return success. Aftershortmoves
(80-140 m),24 outofthe49transfersresultedinasuccessfulreturn,whereasthiswas
soinonly6outofthe 18longer moves(160-240 m).Thedifference,however,wasfar
fromsignificant (p >0.1). It shouldbe noted(1) thateventheshortest distancesof
about80m did neverallowa directviewtothe territorysite (direct viewsalong the
stream were usuallylimitedto< 10m as aconsequenceofdensevegetation ofshrubs
innearlytheentirevalley)and(2)thatseveralotherterritorysites werelocatedbetween
thesitesofthe releaseandtheoriginal territory.
PopulationbiologyofCalopteryxhaemorrhoidalis 17
DISCUSSION
SURVIVAL
Calopterygid damselfliesarewellsuitedforpopulation studiesbyindividualmarking
since they are easily caught andresighted. Thepresent population ofCalopteryx
haemorrhoidaliswas sufficiently small(numbering atmostafew hundred)andlived
inasufficientlyconfinedareatobeefficientlysurveyed, allowing high proportionsof
allindividualstobemarkedandhigh chancestoresightmarkedindividuals.Because
of its isolated habitat,emigration rates will havebeenlow.Theobserved high value
(94%) ofmean daily survivalrateexcludes anyhigh rate ofemigration.
Themean survivalrateobservedinthepresent study (0.94perday) was similarto
rates observedinothercalopterygid species, ranging from0.70to0.98per day(Tab.
IV).Extremelylowandhighvaluesobservedbysomeauthorsdeservecloserinspection.
Thelow(0.70and0.77)figuresinC. aequabilis, reportedby CONRAD&HERMAN
(1990) werefoundin apopulation with a high proportion ofmigrants andtherefore
mayreflecta high daily rate ofemigration rather thanmortality. Theexceptionally
highfigureof0.98inHetaerinacruentatareportedbyCORDOBA-AGUILAR (1994)
was derived (in an unexplained way) from greatly fluctuating individualvalues
(including nonsensevaluesof > 1).Arecalculation, using datashown infigure 3of
TableIV
Published estimates ofmeandailysurvivalratesin Calopteryx,HetaerinaandMnaisspecies
SSppeecciieess CCoouunnttrryy SSuurrvviivvaall SSeexx RReeffeerreennccee
((ppeerrddaayy))
CC..aaeeqquuaabbiilliiss CCaannaaddaa 00..7777 S3 CCOONNRRAADD&&HHEERRMMAANN((11999900))
00..7700 59
CC..aattrraattaa JJaappaann 00..9911** <â3 MM11YYAAIKCAAWWAA((11998822))
00..9933** $$
CC..hhaaeemmoorrrrhhooiiddaalliiss SSppaaiinn 00..9944 <33 pprreesseennttssttuuddyy
00..9944 9$
CC..jjaappoonniiccaa JJaappaann 00..8822//00..8877 6<3 WWAATTAANNAABBEEeettaall..((11999988))
00..9933//00..8877 59
CC.. vviirrggoojjaappoonniiccaa JJaappaann 00..9944** 6c3 MMIIYYAAKKAAWWAA((11998822))
00..9977** 99
HH..ccrruueennttaattaa MMeexxiiccoo ((00..9988))//00..9944**** <33 CCOORRDDOOBBAA--AAGGUUIILLAARR(1(1999944))
MM..pprruuiinnoossaa JJaappaann 00..9944 6<3 HHIIGGAASSHHII((11997766))
MM..pprruuiinnoossaa JJaappaann 00..995555 99 NNOOMMAAKKUUCCHHIIeettaall..((11998888))
eessaakkiiii 00..994444 S<3
ssttrriiggaattaa 00..994477 S<3
* Ascalculatedfromhistogramsofsurvivalrates shownin MIYAKAWA(1982),includingonly survival
between 1to 10daysaftermarking.
** Recalculatedvalue,seetext.
18 J.J.Beukema
CORDOBA-AGUILAR (1994),yieldedanestimateof0.94,andthisfigureismorein
linewithrecordsformean dailysurvivalinCalopterygidae by otherauthors.Exclusion
oftheabove questionedextreme valuesnarrows therangeofpublished valuesto0.82-
-0.97,with apreponderance ofsurvival rates close to 0.94per day (Tab.IV). This
may,therefore,beatypical valueforcalopterygid species.
Survival duringthefirst dayaftermarking appearstobegenerally lowerthanmean
survival, as can be deduced from detailed data given by HIGASHI (1976),
NOMAKUCHI etal.(1988)andownobservations(Fig. 1).Itis questionablewhether
the enhanced disappearance rates immediately after marking point to higher death
rates (by rough handling) or to handling-induced changes in behaviour(stronger
tendency to migrate).
Theabovefiguresformean dailysurvival inCalopterygidae are mostlyhigher than
the values generally recorded in Zygoptera, ranging from0.73 to 0.94 (CORBET,
1999:301). The relatively high valuesfoundinCalopterygidae maypartlybecaused
by their site fidelity, conspicuousness, and tameness. This is especially true for
reproductive malesandmay(partly) explainthedifferentlevelsformalesandfemales
inpercentagesfoundaliveasshowninFigure la.Probably, therewasnorealdifference
in dailysurvival ratesbetweenmalesandfemalesinthestudiedpopulation, since the
datasetsofthetwo sexes showninFigure larun parallel. Differencesbetweenmales
andfemaleswerealsosmallinotherspecies (Tab.IV)andwerenotconsistently higher
ineithersex.
Theeffecton estimatesofsurvivalrates ofoverlooking a certainproportion ofthe
marked individuals can be judged to some extentby omitting all observations on
individualsthatweremarkedshortly beforetheendoftheobservationperiod ineach
year. Ifthecalculationsare limitedtoindividualsthatcouldpotentially beresighted
for>7days, thepercentagesresighted slightlyrosefrom84to86inmaturemalesand
from78to 82inmaturefemales.Notethattheextensionoftheobservationperiod to
>7 daysappearstohaveenhancedthechancetore-encounter afemalemorethanthat
ofamale,as expected fromdifferencesintheirconspicuousness (particularly during
ovipositionfemalesmayeasilybeoverlooked). Thoughallestimatesofsurvivalrates
fromresightings areboundtobeunderestimates,the biasappearstohavebeensmall
inthepresent study.
Ameandailysurvivalrateof0.94,asobservedinthepresent studyforthetwosexes
andagegroups, wouldmean thatthe sizeof the adultpopulation halvesinabout 11
days. This is roughly the durationofthe maturation period in C. haemorrhoidalis
(HEYMER,1973;CORDERO.1989;ownobservations). Maximumlongevity cannot
bestatedexactly, because the numberof very oldindividualsthatcan beobserved
depends amongotherthings on the population size and the searching effort of the
observer (BEUKEMA, 1989). Atthe abovesurvival rate, about 1% ofallemerged
individualswillliveatleast74days as anadult.Inapopulationofthepresentsize, the
maximumadultlifespanwouldthusamounttotwo orthreemonths(ifthere wereno
increasedmortality at highage by senescence). In the field, the oldestindividuals