Possible settlement benefits related to site fidelity for the territorial dragonfly, perithemis tenera (Say) (Anisoptera: Libellulidae)

2005·1.6 MB·English

by  Switzer, P V

Odonatologica34(4):397-405 December I,2005
Possible settlement benefitsrelated
to site fidelity fortheterritorial dragonfly,
pPrithemis tenera(Say)
(Anisoptera: Libellulidae)
P.V.Switzer
DepartmentofBiologicalSciences,EasternIllinois University,Charleston,IL 61920,
United States; - Phone [phone];—Fax[phone];—e-mail [email protected]
ReceivedJanuary8,2005/ReviewedandAcceptedMarch23,2005
Sitefidelity,thetendencytoreturntoapreviously occupiedbreedinglocation,is
commonlyobservedinanimalsandyetoftenthe benefittosuch behavior is unclear.
Inthis study,possible settlement benefitstosite fidelityforP.teneraareexamined,
d3 defend smallmatingterritoriesonpondsand lakestowhich theytypically,but
notalways,returnthefollowingday.Inanobservational study,itwasfoundthat33
did notbecome territorial earlier inthe daywhensite-faithful than when switching
territories. However, 3 3 switching territoriesweremore likelytobe seenexamin-
ingoviposition sites (otherthan the site theyultimately defended)prior tobecom-
ingterritorial than site-faithful 33. Inanexperimentalstudy,it wascontrolled for
differencesin territoryand oviposition site structure,timeofday, evictionsanddis-
turbance,and found thatsite-faithful 33 spentsignificantly less time settling ona
territorypriortodefendingthatterritorythan 3 3settlingatasite forthefirsttime.
Because 3 3examiningsitesare probablymoreatrisk frompredators,this study
suggests that site-faithful 3 3 mayexperiencelowered settlement costs than males
returningtotheiroriginal territory.
INTRODUCTION
Many animalspecies exhibitbreeding sitefidelity, orthetendency toreturn to
a previously occupied breeding location(GREENWOOD & HARVEY, 1982;
SWITZER, 1993;CORBET, 1999). What individualsgain from being faithful
toprevious breeding sitesisoftenunclear;insometaxa,however, anindividual’s
sitefidelityisrelatedtoitsreproductive success. For example, studiesonbirdsand
dragonflieshavefoundthatindividualsaresite-faithfulifthey haveexperienced
reproductive success atthesite inthe past, butunsuccessful individualstendto
398 P.V.Switzer
switch territories(SWITZER, 1993, 1997a, 1997b). Theseswitching individuals
maybeimproving the quality oftheirterritory by changing territories(e.g. BE-
LETSKY & ORIANS, 1987).
Fewstudiesinany taxon haveexamineddifferencesinsettlementbehaviorbe-
tween individualsthat are site-faithfulversus those who are settling on a new
territory(but see,e.g.,EASON & HANNON, 1994;JAKOB etal„ 2001). How-
ever,settlementis a crucialpartofanindividual’soccupation ofaterritoryand
mayinvolvehigh costs; thus, settlementisalikely placeto lookfortheeffectsof
sitefidelity. Whensettling, anindividualthatswitches territorieshastwo gener-
altasks, and both ofthese tasks may bemorecostly thanifthe individualhad
beensite-faithful.
First, an individualmoving to a new territory mustfinda suitable location.
Whensearching foranewlocation, anindividualmayincurcostsrelatedto en-
ergyexpenditure, predationrisk, andmissedforagingormatingopportunities (IS-
BELLetal., 1990;SWITZER. 1993; JAKOBetal„ 2001). Forexample, JAKOB
etal.(2001) foundthattheindividualsofthecolonialspiderMetepeira incrassata
incurred substantiallost feeding opportunities when they movedto a new web
location relative to remaining on the same web. In addition, some studies have
foundthattheearliestindividualsto settlein agiven period are site-faithful(e.g.
FORSTMEIER, 2002);this differenceinorderofarrivalmaybepartlyexplained
by site-faithfulindividualsnot having to searchfora breedinglocation.
Second, once an individualsettles in a particular location, it mustlearn the
characteristics of thatlocation. HINDE (1956) suggested thatindividualsthat
remain in the samelocationbenefitfrombeing familiarwith foragingsites and
predator refuges inthatlocation.Hinde’sargument,whileoriginallyproposed to
help explain thebenefitsofterritoriality,canbeextended toincludethe benefits
ofbreeding sitefidelity(GREENWOOD &HARVEY, 1982).Thus,anindividual
who returnsto aprevious locationmay decreasetheenergy, predation risk, and
lostopportunity costsassociatedwithbecoming familiarwithneighbors, escape
routes,predator refuges andforagingsiteswithinitsterritory(SWITZER, 1993;
STAMPS, 1995;TOBIAS,1997;JAKOB etal.,2001). Although fewstudieshave
examinedsuchconsequencesforsitefidelity,evidencedoessuggestthatfamiliarity
benefitsmay exist forsomespecies. For example, EASON & HANNON (1994)
showedthatwillowptarmigan (Lagopus lagopus) thatinitiallysettlednext to fa-
miliar neighbors hadconsiderably feweraggressive interactions thanthoseindi-
viduals settling next to unfamiliarneighbors. Becausesite fidelityisresponsible
formost of the neighbor familiarity, site-faithfulindividualswouldexperience
lessaggression thanindividualswhowere settling ona newsite.Also, TOBIAS
(1997)foundthattheamount oftimenecessaryto settleterritoryboundariesand
beginforagingcorresponded to thetimedelay fora newly settledEuropean robin
(Erithacusrubecula) becoming dominantonanewterritory.Tobias’resultssug-
gestthatin otherspecies, factors lowering thesettlementtime,such as sitefidel-
Settlement benefitsinPerithemistenera 399
ity,mayincreaseanindividual’sability todefenditsterritory.
Inthisstudy, Iexaminesettlementbehaviorinthe dragonflyPerithemistenera
to test threehypotheses: (1) site-faithfulindividualswill beless likely to search
forotherterritoriesthanindividualsthatare notsite-faithful,(2) site-faithfulin-
dividualswill settleonaterritoryearlierduringaparticularbreeding period than
individualsswitching locations, and(3) site-faithfulindividualswill haveshorter
settlementdurationswhensettling onaterritorythanindividualssettling forthe
first time.I define“settlementduration”narrowly as thelength of timebetween
anindividual’sinitialarrival onthe territorythatperiod and theonsetofterri-
tory defense.
MaleP. tenera defendsmall(approximately 3-5m)breeding territoriesaround
oviposition sites(e.g. a floating stick or clump of vegetation) on slow-moving
bodiesof water (JACOBS, 1955). Although multipleoviposition sites may be
presentwithinamale’sterritory,heonly defends, andcourts femalesat,oneovi-
positionsite(JACOBS, 1955). Malesare only present atthebreeding siteduring
theday(SWITZER, 2002a)andtendtooccupythesameterritorywhenreturning
to thepond thefollowing day (JACOBS, 1955;SWITZER, 1997a, 1997b). This
tendency tobe site-faithfulincreaseswithterritory quality, previous reproduc-
tivesuccess on theterritory,andtheageofthemale(SWITZER, 1997a, 1997b).
Previousstudiesindicatedthatoverall, themales arriving earlieston the pond
tendedtobesite-faithful(SWITZER,2002a).Thus,atthepopulation level, site-
-fidelity seemedtoberelatedto arrivaltime; however, whetherindividualmales
arrived earlierwhen they were site-faithful as compared to shifting territories
wasnot determined.
Upon arrivalatthe breeding area,amale fliesnearpotential oviposition sites
and“examines” themby flying lowandtouching themwithhislegs (JACOBS,
1955;SWITZER, 1995).Afterlocatingasuitableoviposition site, themalebegins
to fly inslow, low circlesofincreasing size inthe immediatearea; thesecircular
flights always includeflying over theoviposition site. Finally, themale perches.
Amalemaystartchasing othermalesfromthearea(i.e.defending histerritory)
eitherduring large circularflights(e.g. circles witha diameterapproaching the
averageterritorysize) or followingperching.
METHODS
This study wasconductedonasmall cattlepondineast-centralKansas, U.S.A.[seeSWITZER
(1995)formoreinformation onthestudy site]. Theperimeterofthepondwasmarkedwith survey-
or’s flagstofacilitate recordinglocations. Males werecapturedand marked ontheirforewingwith
a permanent marker. Individuals marked in thismannercouldbe identified without recaptureus-
ingbinoculars.
OBSERVATIONALDATA —In 1992,datawereobtained onthearrival timesandlocations of
males aspart ofalargerstudyofterritorialityandhabitat selection(e.g. SWITZER,1997a,2002b),
Torecordthelocations ofmales,thepondwascontinuouslyscansampled(atapproximately2minute
400 P.V.Switzer
intervals);duringthese scans,Irecordedthelocations ofanynewmalesand anychangeinthe loca-
tion ofexisting males. Icategorizedamaleasbeingsite-faithful ifhe defendedanovipositionsite
within 3moftheprevious day’sovipositionsite(SWITZER, 1997a).Threemeters is theapproxi-
mate,minimumterritorydiameterforP.tenera(JACOBS, 1955;SWITZER&EASON,2000),From
thesedata Icould establishamale’s arrivaltime (i.e.when hefirstbegandefendingaterritory)and
whetheramalewassite-faithful between days.Notethatamalemay havearrived atthepondprior
tobeingobserved defendingaterritory;therefore,Ialsorecorded theidentityand location ofmales
who wereexaminingsiteswhen possible.
Data foranalysesofsiteexamination andarrival timerequiredsomemanipulationtocontrolfor
possibleconfoundingvariables. First, Iexamined the relationshipbetweensite-fidelity and thelike-
lihood ofamale beingseenexaminingsitesother thanhis eventual territory.For thiscomparison,
Ifirstdid anoverall testpoolingacrossmales,and thendid a pairwisecomparisonofoccurrences
withinmales usingMcNemar’s test(ZAR, 1999).Becausesomemaleshad multiplemovesthat could
qualify,forthe within-male comparisonIusedthefirstmoveofeachtype(i.e.site-faithfulorswitch-
ingterritories)for eachmaletoavoid pseudoreplication.
Second,becausetimeofarrivalwillbeaffectedbyweatherconditions (SWITZER,2002a),Istand-
ardizedarrival timebycalculatingitrelative towhen thefirstmalesettledonthepond.Forinstance,
ifthefirstmalearrived at 1000 hr, andthe maleofinterestarrived at 1030 hr,then thearrival time
forthatmalewouldbe30min(SWITZER,2002b).Also,tocontrolforpossible,confoundingeffects
frombeingevictedfromaprevious territory(SWITZER,1997a),Ionly included data formalesthat
hadnotbeenevicted fromtheirpreviousday’sterritory.Consistent differencesexistedin thearrival
times amongindividual males (SWITZER,2002b);thatis, some malesconsistentlyarrived earlier
than other males.To take these differencesamongmalesinto account,analysesofarrivaltime used
pair-wisecomparisonswithinanindividual male,comparinghisaveragetimeofarrivalwhen hewas
site-faithful versuswhen hechangedlocations. Intotal,12malesmetthesecriteria forthepair-wise
comparison.
SETTLEMENTDURATIONEXPERIMENT — Inorderto examine thesettlement duration
onaparticularterritory,Iconductedamorecontrolled experiment duringJulyand August, 1994in
which Ifocusedindetail onaparticularareaofthepond.Duringthestudyperiod,individuals were
continuallymarked and thestudyareawascontinually observed.Ithereforeknew whichmales had
experienceatovipositionsites in thestudyareathroughouttheduration ofthestudy.
Clearly,the typeofovipositionsubstrate couldhaveaneffectonhowlonganindividual took to
settle atalocation. Consequently,tostandardize ovipositionsites asmuch aspossible, I removed
naturalovipositionsubstrate inthe studyareaandreplacedthem withconstructed sticksforuseas
ovipositionsites(seeSWITZER, 1997b foramoredetailed descriptionofthese ovipositionsticks).
BothmaleandfemaleP.tenemreadilyused theprovidedsticksassuitableovipositionsitesandthese
stickswereusedforall observations.I alsoplacedsticksforperchesneareachovipositionsite.
Toobtainthesettlement durationforamale,focalobservationsweredoneonthestudy area.Ar-
rivingmales weretimed with adigitalstopwatchasthey arrivedand examined specificoviposition
sites.Todefinetheonsetofterritorial defense,Ididnotwaituntilthefocalmaleactuallydefendedhis
site,becausethisbehavior wouldhave beennecessarily dependentonthearrivalofintrudingmales.
Instead,I defined“settlement duration”asthetime betweenwhen amalefirststartedexaminingan
ovipositionsite untilhe stoppedexaminingthesite and eitherperchedorbeganflyingin largecir-
cles, Typically,aresidentwill pursueintrudersifhehasreached thestage offlyinginlargecirclesor
perchingonhis territory(personalobservation).
Thedesignofthisstudyalso controlled fortwo additional confoundingvariables.First, ifamale
orafemaleinterruptedasettlingmale,histimewasnotincluded in theanalysis. Second,tocontrol
foranypossibletirae-of-dayeffectsonsettlementtime,onlymalessettlingwithinthefirstthreehours
ofPtenemoccupationonthepondthatdaywererecorded. Thistime periodincluded themajorset-
tlement periodfortheday(SWITZER,2002b).
SettlementbenefitsinPerilhemis tenera 401
Idefined“naive” individuals asthoseindividualswhodid nothaveanypreviousexperienceatthat
particularoviposition site.Thus,althoughnaiveindividuals may havebeen territorialat otherloca-
tions,theyhad noexperienceatthe sitein question. Incontrast,“site-faithful”individuals had de-
fendedthatparticularoviposition site theprevious day.
Non-parametricstatistics taketied-values into accountwhen appropriate.All meansarereport-
ed±S.E.
RESULTS
SITEEXAMINATIONANDTHETIMEOFTERRITORYSETTLEMENT
Following theirarrival at thepond, malesthatwere not site-faithfulweresig-
nificantly morelikelythansite-faithfulmalestobeobservedexamining sitesother
thantheoneinwhichthey eventually settled.Whensettlementdatawerepooled
foralldaysforallmales, maleswereseenexamining before23/59(39%)switching
daysversus 3/72(4%)ofsite-faithfuldays(\2=24.7,df= 1,P<0.0001).Thepat-
ternalsoheldwhenawithin-malecomparison wasmadeforthosemalesthatwere
both site-faithfulandnot site-faithful(ondifferentdays)(Fig. 1;McNemar’stest;
binomial P = 0.01). For the
onset ofterritorialbehavior,
however, no significant pat-
ternexisted. Sevenoutofthe
12individuals(58%)whomet
the criteria for the pairwise
comparison settled earlier
whensite-faithfulthanwhen
theyweresettlingonnewter-
ritories (median overall dif-
ference= 10.8minutessooner
when sitefaithful; Wilcoxon
signedrank test,n= 12,T=
34, P=0.69).
SETTLEMENTDURATION
Fig. 1.Within-malecomparisonofwhetheraP.teneramale
Although all settlement
wasobservedexaminingsitesotherthanhiseventualterritory
durations were relatively onlywhenhewassite-faithful (SF),onlywhennotsite-faith-
brief, once they arrived at a ful(NSF),whenboth SFandNSForwasnoteverobserved
site, site-faithful males took examiningsitespriortosettlement. Onlythe 17males that
significantly less time when hadatleast onedayinwhichtheyweresite-faithful andone
settling on their territories dayinwhichtheywerenotsite-faithful wereincluded inthe
analysis.Forthose males thathad morethan oneday that
than didnaive males. When wasSForNSF thefirst observation (chronologically)was
each individualcontributed used ineachcategory.
402 P.V.Switzer
only one observationto the anal-
ysis, naive males spentalmost five
timeslonger settling thansite-faith-
fulmales(Fig.2; Mann-Whitney U,
T=l,P <0.001).
The pattern of decreased settle-
ment time for site-faithful males
holdswhen looking within individ-
uals. A comparison of naive ver-
sus site-faithfulsettlementtimes re-
vealedthatthesameindividualspent
moretimesettling whenhewasnew
to a sitethanwhenhereturnedto a
Fig. 2.Averagesettlement time (± SE) fornaive(N
= 11;median 45s) andsite-faithful(N=11;median familiarsite(median difference=28
7 s)maleP. tenera. s; N =7;WilcoxonMatched-Pairs;
T = 0; P < 0.018). Age could be a
possible confounding variablewiththeseresults,becausenaivesettlementsmight
be before site-faithfulsettlementsin most cases. However, for2 of the7 males
used inthe within-malecomparison, the site-faithfulobservationcamepriorto
the naive observation; thus they wereolderforthe naiveobservation. Forboth
ofthesemales,thenaivesettlementtimewas longerthanthesite-faithfultime.In
addition,thespecific oviposition site did notseemtoaffect thepatternbetween
differentsite-faithful and naiveindividuals (e.g., site 128, site-faithful males, N
=4, 8.0± 3.9sec.; naivemales, N = 7,57.9 ± 8.5sec.; Mann-Whitney U,T =0,
P<0.005). Finally, thesettlementcomparison maybefurtherlimitedto thefour
malesforwhichIhaveboth day 1 (naive) andday2(site-faithful)settlementtimes
atthe sameoviposition site.Allfourmalestookless timesettling whensite-faith-
ful,although this sample is too small for statistical comparison.
DISCUSSION
Previous research foundthat the earliest P. tenera males to settleon territo-
ries weremorelikely tobesite-faithfulthanthe lastarrivingmales (SWITZER,
2002a). However, thecurrent study foundthatanindividualmaledidnot tend
to settleearlier on the days thathewas site faithfulas compared to thosedays
in which heswitched territories.Thisindicatesthat although atthe population
leveltheearliestmalesto settlemightbesite-faithful, nooverallrelationship ex-
istsbetweensitefidelityandtimeofsettlement.Consequently, ifearly settlement
yields any benefitsinP. tenera,suchbenefitsare notbeing accrued bysite-faith-
ful individualsmorethanbyindividualsswitching locations.
At aparticular site, however, the results indicateasubstantialdifference be-
tween naiveandsite-faithful malesinthetimeit takes fromarrival to becoming
Settlementbenefitsin Perithemis tenera 403
territorial.Thestudy designeliminatedthepossibility thatthis differencecould
be explained by oviposition substrateor location.In addition, neitherthe spe-
cifictimeof day nor disturbance fromotherP. tenera couldbe responsible for
increased timefornaiveindividuals.Age couldbeapotential confounding vari-
able, becauseage affects site-fidelity inP. tenera andotherspecies (SWITZER,
1997a; KEMP, 2001). However, thetwo malesforwhichsite-faithfulsettlement
preceded naive settlementbothhad longersettlementtimes whennaive.There-
fore, overall thedatasuggest thatsite-faithfulmales doneedashorteramount
oftimethanmalesnewto asite.Ifsettlementtimeis positivelyrelatedto settle-
ment cost, perhaps because ofincreasedpredation risk, missed mating oppor-
tunities, orestablishmentofpriorresidency advantage, thentheseresults would
indicate thatsite-faithfulmaleswouldexperience alowered settlementcostrela-
tiveto naivemales.
Ofthesepossible costs,predationrisk ismorelikelythanmissedmatingoppor-
tunitiesor priorresidency advantage. Malesexamining sites maybemore likely
tobe eaten bypredatorsthanterritorialmalesthatare notengaged inmatingor
fighting (JACOBS, 1955;SWITZER, 1995). Indeed, anecdotally it seemseasier
forhumansto capturemalesthatare examining sites than to captureterritorial
males. Although females are likely to desert amale who has not established a
territory(SWITZER, 1997b),males tendtoestablishterritories prior to female
arrival (JACOBS, 1955;SWITZER, 2002b),whichmakesmissed matingoppor-
tunitiesunlikely. Furthermore, priorresidency advantage is typicallyonly asso-
ciatedwithnonescalatedinteractionsbetweentheresidentandintruderinwhich
the intruderis examining the oviposition site; whenactual contests foroviposi-
tion sitesoccur,noresidency advantage exists (SWITZER, 2004).
Though the results indicateda cleardifferencebetweenthe settlementdura-
tionsofsite-faithful andnaivemales, theoverallsettlementtimeswerequitebrief,
whichbegsthe question ofwhetherthesetimedifferencesare biologicallysignif-
icantorjust statistically significant. However, focusing onjust this briefdiffer-
enceintimeis likelyto misrepresenttheactualsettlementcostdifference fortwo
reasons. First, my experimental sites werestructurally very simple; theyconsist-
edofasingle, shortoviposition stickfloating inthewaterwithafewsmall,thin
sticks projecting fromthewater forpossible use as perches. By design, allother
floatingandemergentvegetation hadbeenremoved. Thebehaviorexhibitedby
asettling male— circlesof increasingsize which includethe oviposition site —
seemsconsistentwiththehypothesis thatamale’ssettlementbehaviorallowshim
to learnthelocationofhis oviposition site sothathecan takea femaledirectly
tohis sitewithoutwandering; afemalewill desertamaleifhedoesnot takeher
directlytohissite(SWITZER, 1997b).Ifthis hypothesis werecorrect,thenmore
structurally complex habitats wouldlikely provide a morechallenging task for
spatial learning. Consequently, amorenaturaloviposition siteandterritorymay
leadto longersettlementtimesformalesandperhaps larger differencesbetween
404 P.V.Switzer
site-faithfulandnaivemales.
Second, malesshifting sites were morelikely tobe seen examiningother sites
thansite-faithful males. As statedabove, examinationof sitesis costlybehavior;
notonlydoesittaketime,butitpotentiallyexposesmalesto predators(JACOBS,
1955;SWITZER, 1995). Thus, malesreturning to aprevious day’sterritorymay
besubstantially lowering theirpredation risk.
Interestingly,onaveragemalesinitiatedterritoriesatthesametimewhenshift-
ing territories as when site-faithful, and yetmales were morelikely toexamine
sitespriorto settlingwhenthey shiftedterritories.Thisresultleadsto theinterest-
ing possibility thatmalesthatshifted sitesmighthavebeenarriving earlieratthe
pond tocompensatefortheirneedto findanew,suitableterritory.Indeed, males
that shifted sites wererarely seen at theirprevious territory, whilesite-faithful
malesarrived attheirprevious territoryimmediately. Thispatternindicatesthat
any “decision”to switch sites likelyoccurs priortoarrivalat thepond; therefore,
the opportunity forarriving earlierto compensatefor changing territories is at
least logistically plausible. At thispoint, however, this idea remainsspeculation
andawaits futurestudy.
ACKNOWLEDGEMENTS
Iwould like tothank A.B. SWITZER,C. SCHIF and D.SCHIFfor hospitalityand accessto
thestudypond,A.M.SWITZER andJ.SWITZERfor assistancecollectingdata,and P.EASON,I.
SWITZERand L. SWITZERforcommentsonanearlierversion ofthis manuscript.
REFERENCES
BELETSKY,L.D.&G.H.ORIANS, 1987.Territorialityamongred-wingedblackbirds. 1.Sitefidel-
ityand movementpatterns.Behav. Ecol. Sociobiol. 20: 21-34.
CORBET, P.S., 1999. Dragonflies:behaviour andecologyofOdonata,HarleyBooks, Martins.
EASON,P.&S.J.HANNON, 1994.Newbirdsontheblock:newneighborsincreasedefensivecosts
forterritorial malewillowptarmigan.Behav. Ecol. Sociobiol. 34: 419-426.
FORSTMEIER,W, 2002.Benefitsofearlyarrivalatbreedinggroundsvarybetween males,J.Anim.
Ecol. 71; 1-9.
GREENWOOD,P.J.& P.H.HARVEY,1982. Thenataland breedingdispersalofbirds. Amu. Rev
Ecol. Sysl. 13: 1-21.
HINDE, R.A.,1956. Thebiologicalsignificanceofthe territoriesofbirds. Ibis98: 340-369
ISBELL, L„ D.L. CHENEY& R.M.SEYFARTH, 1990. Costs and benefits ofhome range shifts
amongvervetmonkeys(Cercopithecusaethiops)inAmboseli National Park.Kenya.Behav.
Ecol. Sociobiol. 27: 351-358.
JACOBS,ME.,1955. Studies onterritorialism andsexualselection indragonflies.Ecology36: 566-
-586.
JAKOB,E.M.,A.H.PORTER&G.W.UETZ,2001. Sitefidelityand thecosts ofmovementamong
territories: Anexamplefromcolonial web-buildingspiders.Can. J. ZooI. 79;2094-2100.
KEMP,D.J., 2001. Age-relatedsitefidelityin theterritorial butterflyHypolimnasbolina (L.)(Lepi-
doptera;Nytnphalidae).Ausl. J.Ent. 40:65-68.
Settlement benefitsin Perithemistenera 405
STAMPS,J.A., 1995. Motor learningand thevalue offamiliarspace.Am. Nat. 146:41-58.
SWITZER, P.V., 1995. Influencesonthe sitefidelityofterritorial animals: theoretical andempirical
studies. Ph.D. diss.Univ. California,Davis.
SWITZER,P.V., 1997a.Pastreproductivesuccessaffectsfuture habitatselection. Behav. Ecol. So-
ciobiol. 40: 307-312.
SWITZER,P.V., 1997b.Factors influencingthe site fidelityofaterritorial animal,Perithemisten-
era.Anim. Behav.43: 865-877.
SWITZER,P.V.,2002a.Territoryquality,habitat selection,andcompetitionintheamberwingdrag-
onfly, Perithemis tenera(Odonata;Libellulidae): populationpatterns asa consequenceof
individual behavior. J. Kans. ent.Soc. 75: 145-157.
SWITZER,P.V., 2002b. Individual variation intheduration ofterritoryoccupationbymalesofthe
dragonflyPerithemis teneraSay (Odonata:Libellulidae).Ann.ent.Soc. Am. 95;628-636.
SWITZER,P.V., 2004.Fightingbehavior andprior residencyadvantageintheterritorial dragonfly,
Perithemistenera.Ethol. Ecol. Evol. 16:71-89.
SWITZER,RV.&P.K.EASON, 2000. Proximateconstraints onintruderdetection in thedragon-
flyPerithemistenera(Odonata;Libellulidae):effectsofangleofapproachandbackground.
Ann. ent.Soc. Am. 93: 333-339.
TOBIAS,J., 1997. Asymmetricterritorial contestsintheEuropeanrobin:therole ofsettlementcosts.
Anim. Behav. 54:9-21.
ZAR,J.H., 1999.Biostatisticalanalysis,[4thedn]Prentice-Hall,UpperSaddleRiver,N.J.