Territoriality in Notiothemis robertsi Fraser (Anisoptera: Libellulidae)

11 Pages·1996·1.8 MB·English

by  Clausnitzer, V

Odonatologica25(4):335-345 December 1, 1996
Territoriality inNotiothemisrobertsi Fraser
(Anisoptera: Libellulidae)*
V.Clausnitzer
Kirchweg 5,D-35043 Marburg,Germany
ReceivedFebruary 20, 1996/Revised andAcceptedMay8, 1996
The study was carriedoutat small pondsin theKakamegaForest, arain forestin
WestKenya.89 6 i weremarkedindividuallyand territorial onesobserved foratotal
of3171 min.Malesbehaveterritoriallyforameanof 14days,amaximumof45 days.
Intruders aredrivenoutbytheresident anddonotshow offensivebehaviour. Different
activities ofterritorial c?<? aredistinguished.Mostofthe time themale spendsperch-
inginthe territory(32%oftotal timein territory).Sunflightstothe tree tops arethe
most frequentflightactivity.
INTRODUCTION
The behaviouroftropical Libellulidaehasattractedmoreandmoreattentionin
the recent years (e.g. MILLER, 1983,MILLER& MILLER, 1985, 1991;PARR,
1980;SORIANO, 1987).Thereis still alackof informationforspecies inhabiting
tropical rain forests and only a few authors have paid attentionto them(e.g.
CORBET, 1962; LEGRAND, 1979; LEMPERT, 1988; MILLER, 1993, 1995;
PARR, 1980).Thispaperdealswiththesofarscarcely studiedrainforestLibellulidae
(Tetratheminae) NotiothemisrobertsiFraser, 1944.
Therangeofterritorialbehaviourinmaledragonflies is wide,butseems tohave
mainly onecommonpurpose: theaccess tofemales(EMLENetal„ 1977).Territo-
rialityisalso describedas astrategy tominimiseintraspecificaggression (POETHKE
& KAISER, 1987).Agrowing numberofmales atthemating places canleadtoan
intensificationof territorial behaviour, e.g. in Acisoma panorpoides inflatum
(HASSAN, 1978), Nesciothemis nigeriensis (PARR, 1983a), Corduliaaenea
* Dedicatedtothe memory ofthe lateDr PeterL. MILLER
336 V Clausnitzer
amurensis(UBUKATA, 1975)andAeshna cyanea(POETHKE&KAISER, 1987)
or to a collapse oftheterritorial system, e.g.in Libellulasaturata (DEBANG,
1993).
Theexpression ofterritorialbehaviouris influencedby frequency, numberand
availability ofreceptive females.Further thelife span ofthe individualsandthe
possible occurrence ofseasonality influencesterritoriality.Specieswithavery lim-
itedtemporal appearanceatthemating places will spendmoreenergyinshorttime
actions than those with less limitedmating periods. Thelatter wefindmainly in
tropical rain forests, because ofthelack ofastrong seasonaleffect (GAMBLES,
1960).Thecostsandthebenefitsanindividualmaleexperiences willhelpto deter-
minetheevolutionofa specific territorialbehaviour(BROWN, 1964).
Muchhasbeen writtenabouttheestablishmentofterritoriesin dragonflies (e.g.
ALCOCK, 1987;BICK&BICK 1965;CAMPANELLA&WOLF,1974;HARVEY
& HUBARD, 1987;MILLER, 1983;PAJUNEN, 1966).Someauthors,e.g.MOORE
(1987),andPARR (1980, 1983b) give quantitative analyses ofmaleterritoriality.
This study is focussed onterritorialactsofmaleNotiothemisrobertsi,giving con-
siderationstothepurposeandfunctionalexplanations ofthem.
Theterm“territory” inthispaperis usedaccording tothedefinitionofNOBLE
(1935) as “any defendedarea”. The territories are established by the males near
waterbodiesto gain access tofemales.Theterritorialperiodof thestudiedspecies
differsfromother dragonflies in length, a reduced intraspecific aggression anda
low mating success (PARR, 1983a).The territorialmaleshows two majoractivi-
ties: perching andflying(definitions inMAY, 1976). Thelatteris furtherdivided
into patrolling, interspecific, intraspecific, inspection, sexual and sun flight(Tab.
I). Feeding doesnot occurin orneartheterritories(MOORE, 1987).
N.robertsibreedsinsmallshady pools inrainforests, isunspectacular andeasily
overlooked. Theonly detaileddescriptionsofbehaviourandecology are given by
LEMPERT(1988). Thestudy sitein theKakamega Forestwas smallandobserva-
tionswereeasy tomake.Atthesametimetwo otherspecies oftheTetratheminae-
NotiothemisjonesiRis, TetrathemiscorduliformisLongfield -occurred atthepools.
Allthree species are similar inbody shape, colourandbehaviour.
METHODS
Notiolhemis robertsi wasstudied intheKakamegaForest(00°08' -00°24’N,34°20'- 34°33’E;alt.
1500-1700 m), WestKenya,at a small pond complex formed by gold-diggersalongtheLugusida
River. 89 males weremarked individuallywith numbers (permanentpen EDDING 780 /silver) and
released immediatelyafter capture. Placing theanimals with its legs onvegetationthey showed no
escape reactions andterritorial males resumed normal behaviour intheirterritories immediatelyafter
capture (PARR & PARR, 1974). The marked dragonfliescould be recognisedeasily with a short-
-focus binocular (8 x 30) withoutcatchingthe animals again. Observations were made between 2
December 1994and 10February 1995 on56 daysbetween 10:00and 16:00hlocaltime, whenthe
maleswereactive attheponds.Astop-watchand adictatingmachine wereusedtotime anddescribe
Territorialityin Notiothemis robertsi 337
the observed activities. Some behavioural patterns were filmed (PANASONIC, NV-GIE) and ana-
lysedlater.Forty males wereobserved foratleast 20minuteseach (max.265 min; total: 3,171 min).
The flighttypes wereclassified into patrolling,interspecific,intraspecific,inspection, sexualand sun
flight(Tab. I).Each ofthesebehaviours is distinguishableby flight.
Table I
Classification ofdifferent flight componentsin territorial maleNotiothemisrobertsi
BBeehhaavviioouurr IInniittiiaattiioonn OOrriieennttaattiioonn DDeessccrriippttiioonn
PPaattrroolllliinngg SSppoonnttaanneeoouuss IInnddeeffiinniitteeiinnssiiddeetthhee SSllooww;;hhoovveerriinngg,, sshhoorrtt
tteerrrriittoorryy ddiissttaanncceeoovveerrtthhee wwaatteerr
IInntteerrssppeecciiffiicc c6?6d ooffootthheerrtteerrrriittoorriiaall TToowwaarrddssootthheerr mmaallee RRaappiidd,, ddiirreeccttaapppprrooaacchhffrroomm
ssppeecciieess,, mmaaiinnllyyOOrrtthheettrruumm ssiiddeeoorrbbeellooww,,ssoommeettiimmeess
sstteemmmmaallee ccllaasshheess
IInnttrraassppeecciiffiicc i66i ooffNN..rroobbeerrttssii TToowwaarrddss iinnttrruuddeerr RRaappiidd,, ddiirreeccttaapppprrooaacchhffrroomm
ssiiddeeoorrbbeellooww,,rraarreellyyccllaasshheess
IInnssppeeccttiioonn MMoovveemmeennttooffoobbjjeeccttsswwiitthh TToowwaarrddss oobbjjeeccttbbeeiinngg DDiirreecctt,,hhoovveerriinnggbbeeffoorree
ssiimmiillaarrssiizzeeooff22 iinnvveessttiiggaatteedd oobbjjeecctt
NN.. rroobbeerrttssii
SSeexxuuaall fflliigghhtt 22NN..rroobbeerrttssii,, TToowwaarrddss ccoonnssppeecciiffiicc RRaappiiddaanndd ddiirreecctt,,
NN..jjoonneessii,,TTeettrraatthheemmiiss ffeemmaalleess,,wwhhiicchh ddoonnoott ccaappttuurree ooffffeemmaallee
ccoorrdduulliiffoorrmmiiss sshhoowweegggg--llaayyiinngg
bbeehhaavviioouurr
SSuunn fflliigghhtt ??LLoonnggsshhaaddyyppeerriiooddss TToowwaarrddss ttrreeeeccaannooppiieess DDiirreecctt aanndd lliinneeaarr ttoowwaarrddss
ttrreeeettooppss;;mmaaiinnllyyuussiinnggtthhee
ssaammeerroouuttee
Sun flights interruptedthe observationperiod,hence theindividuals could notbe observed any
longer. SometimesIcould followamalewith thebinoculars and foundthemperchingin sunspotsin
the tree tops.
In order to determine how new arrivingmales establish territories, Iremoved males, which had
beenterritorialforseveral daysbefore. Thiswaseasy,because sizeandlocation oftheterritoriesnever
changed.Experiments with the “Fishing-line”techniquewerecarried outon territorial males. In this
studyIused livingspecimen ofnormal maleswhich werepresentedtoterritorial males. MalesofN.
robertsi showednoreaction to dead individuals presentedtothem.Theexperimentalinsectsweretied
with acottonthread, attached between the fore and hindwings and tying the hind legs. A detailed
descriptionofthisapplicationofthe “Fishing-line”techniqueisgiveninMOORE (1952). Duetothe
small size ofN. robertsi the “Fishing-line”techniquewas difficulttoapply(PAJUNEN, 1964a),The
experimentalinsects sufferedfromthetiedcottonthreadand duringtheexperiments,e.g.thewingsor
wingveinsbroke. Henceonly a limited numbef(n= 10) ofexperimentswerecarried outat different
timesofthe day.
RESULTS
Seventy-one percentofthe89markedmalescouldbeobserved atleastasecond
timeand56% ofthemaleswere seenmore than twice attheponds. Despite spe-
cificsearches, noneofthemarkedanimalswererecordedatotherponds.Thelong-
estperiod betweenfirstandlastobservationofamature malewas 62 days(Fig. I).
338 V.Clausnitzer
Males were territorialonly forone time intheir lifespan. Forty-five percent of
the markedmalesobtainedaterritory duringthe observationperiod. The length of
theterritorialperiod was variable,butcouldextendto43 days.Aftertheterritorial
time the males were seen again for amaximum ofone more day. SometimesI
foundamaledeadinthewater ofaterritoryithadoccupied (Fig. 1).
Fig. 1. Periodspent as aterritorial male and total observation lengthofsome individuallynum-
bered males ofNotiothemis robertsi.
Malesarrivedinaterritory(single roundpools; ca.2min diameter)only inthe
morning (10:00-11:30 h).Newarriving malesneversucceededin winning territo-
rial interactions.Long and aggressive fights couldbeobserved only on veryrare
occasions and then it was always the resident who won. A territory, where the
current owner was removedat 11:30h or laterremainedempty fortherest ofthe
day. The results fromthe “fishing-line” experiments showed in over 50%ofthe
tests anattack fromtheresidentmale.Theattacks were very shortand couldnever
be provoked a second time. No evidence forsexually motivated flights towards
tiedanimals were observed.
Territorialmales startedactivities at theponds between 10:00and 11:00h. In
cloudy weatherthey disappeared tothetree-tops.They perched on smallvantage-
-points, whichallowed a good viewoftheirterritory. Fromthispoint they started
theirflights. Thedetailedobservation of the maleno. 4from 10:00-14:00hon 5
TerritorialityinNotiothemis robertsi 339
TableII
Flightactivities ofonemale Notiothemisrobertsi (No.4)inhisterritoryon5-XII-1994; at 13;30h
clouds appearedand at 14:00hthe male left the territorybecause ofcloudiness
h 10:00- 10:30- 11:00- 11:30- 12:00- 12:30- 13:00- 13:30- 10:00-
10:30 11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:00
Totaltimespendin 5.67 5.07 12.52 12.67 11.48 29 24.8 20.07 121.29
territoryin min
No. offlightsout of 7 14 17 16 11 0 5 5 75
territory
Mean time in territory48.57 21.79 44.18 47.5 62.64 1740 297.6 240.8 97.03
ins.(min/max) (5/128) (8/42) (5/101) (5/99) (52/91) (-/-) (273/150)(137/400(5/401)
Total flightin timein s, 29 48 74 57 86 30 36 34 394
(%) (8.53) (15.58) (9.85) (7.5) (12.86) (1.72) (2.42) (2.82) (5)
No. offlights 6 13 22 14 23 15 18 17 128
(permin) (1.06) (2.56) (176) (11) (2) (0.97) (0.73) (0.85) (104)
Meanduration ofeach 4.83 3.69 3.36 4.07 3.74 2 2 2 3.08
flightins.(min/max) (1/12) (2/6) (1/5) (1/9) (1/16) (1/3) (1/5) (1/5) (1/16)
Patrol 3 6 18 II II - 4 7 60
(%) (50) (46.15) (81.12) (78.57) (47.83) (22.22) (46.67) (46.88)
Aggressive flights - 3 2 - 1 - 1 1 8
(%) (23.08) (9.09) (4.35) (5.56) (5.88) (6.25)
Inspection 3 4 2 3 9 15 II 9 56
(%) (50) (30.77) (9.09) (21.43) (39.13) (100) (61.11) (52.94) (43.75)
Otherflights(sx: - - - 2(a) - 2(sx) - 2(sx)
sexual; a:avoiding) 2(a)
%ofpoolsunny - - 5-10 - - - 10 5 -
Decembergives animpression oftheactivitiesofN. robertsi (Tab.II).
Allobservationsofthevari-
ous flightactivitiesofterrito-
rial males were totalled and
setin relationto therespec-
tivehour.Thisgaveageneral
diagram ofthe daily routine
concerning the flight-behav-
iour a male of N. robertsi
showed in his territory (Fig.
2).Inthecourseofa day im-
Fig. 2. Average number ofthe flightactivities per hour of
portance of different flight territorial male Notiothemis robertsi in histerritorybetween
activities of territorial N. 10:00-16:00 h (n= 1691;in brackets n perh).
340 V. Clausnitzer
robertsishifted.Patrolling and interspecific flights decreasedandthelatterdisap-
peared intheafternoon,whileinspection flightsandsexualflights increased.
Focussing on thepossible functionsofthe differentbehaviouralacts I counted
thetotal numbersofeachbehaviouras afirst or asecond act (Tab. III). Themost
commonbehaviourwas perching with32% followedby sunflights with 28%and
patrolling with 27% of the observed behaviours. Inspection, intraspecific,
interspecific andsexual flightsoccurred less frequent.
Table III
Two-act sequencesinthebehaviour ofterritorialmalesofNotiothemisrobertsi. - [Thenumbers show
theobserved action followingadistinctprecedingbehaviour (n=2777)]
Followingaction
Preceding Perch Sun Patrol Inspec- Inter- Intra- Sexual Total
behaviour flight tion specific specific flight
Perch _ 489 203 142 151 51 16 1052
Sun flight 396 - 270 - 18 17 - 701
Patrol 333 84 - 1 22 11 1 452
Inspection 90 25 7 - 7 - - 129
Interspecific 240 80 14 4 - 3 - 341
Intraspecific 16 15 28 - 1 - - 60
Sexual flight 10 7 2 - - - 23 42
Total 1085 700 524 147 199 82 40 2777
Over forty-onepercentofallflights were“sun flights” to sunny spots inor near
thetree tops(Fig. 2,Tab.III).
The time a male spent con-
tinuousatafullsunnyor afull
shady perch in the territory
beforeleaving forasun flight
was totalled and compared
(Fig. 3).As thisis a very sub-
jective methodIdid not con-
sider perched males in twi-
Fig.3.PercentageoftimeofamaleNotiolhemisrobertsispent lightor wherethe exposition
at full sunny (n= 247) orfull shadyperches (n=86) before changed duringtheperching
leavingforasunflight.The totaltimespent at each position time.
correspondsto 100%.
DISCUSSION
Notiothemisrobertsidoesnotshowseasonality andlarval development lasts two
months (LEGRAND, 1977).Thisfits theobservationsfor manytropical species,
wheretheadultlifeexceeds thelarvallife (GAMBLES, 1960).Thelong life-span
andthelack ofseasonality isassociatedwithalong territorialperiod (average: 14
Territorialityin Notiothemisrobertsi 341
d; max: 43 d; n= 31). Formanylibellulidsmuch shorterterritorialtimes are de-
scribed (e.g. JACOBS, 1955;PAJUNEN, 1966;CAMPANELLA, 1975). In N.
robertsithecompetition forterritoriesis lowandaresidentisrecognized andac-
cepted by intruders.Other libellulidsshowoften a greatdealofphysical aggres-
sion toestablish and to keep territories(e.g. PAJUNEN, 1966;PARR & PARR,
1974). The slowestablishmentofnew territorialmales in N. robertsi is possible
becauseofthelonglife-span andnon-seasonalbreeding behaviour.DAVIES(1978)
describessimilarresults fromtheSpeckled WoodButterfly Pararge aegeria. They
can perform such a defensive behaviour, because there is a high probability of
finding anotherterritoryandthenon-territorialmaleshavea90%chancetoestab-
lishanown territorylater withoutfights. Territorialfights in dragonflies between
the intruderand the resident cost energy which reduces theirterritorial time
(MARDEN, 1989;MARDEN & WAAGE, 1990). As femaleN. robertsi appear
very rarely attheponds (CLAUSNITZER, 1995) thelength oftheterritorialperiod
is very importantformalestoobtainsuccessful copulations.
Territorialmalesspend mostofthe timeperching. Only 5% ofthetotaltime in
theterritoryare spentinflightactivities.This classifiesN. robertsias a“percher”,
like many species oftheLibellulidae, e.g. Trithemis, Nesciothemis, Sympetrum,
Diplacodes and Urothemis (PARR, 1983a). Perching is one way of dragonflies
inhabiting shady rain-forest pools to save energy (SHELLY, 1982). The impor-
tanceofthelatterwillbeshowninthereasons andfunctionsofthedifferentflight
activities practised by territorialmaleN. robertsi(Tab.I).
Thetotal numberofflights decreaseswith thetimeoftheday(Fig. 2).An aver-
ageof43.6differentflightactivitiesbetweenthehoursof 10:00and 11:00halves
toonly 24.6flight activitiesbetweenthehours of 15:00and 16:00,This isbased
mainly on areductionofpatrollingandintraspecific flights andcorresponds with
theestablishmentofterritoriesonly inthemorning hours.
REASONSFOR,ANDFUNCTIONS OFTHEDIFFERENT BEHAVIOURS
An importantfactoris the shady environmentofthemating places. Overforty-
-onepercent ofall flights were sun flights. Thetotal numberofsun flights
perhourdoesdecreaseonly very little(Fig.2) overthe day. Seventy percentofall
sunflights followperching (Tab. III). Overfiftypercentofthemales perching ina
shady position haveleftforasun flightafter30seconds. Only twelvepercentstay
longer than 60seconds incomparison toover45%ofthemalesperching insunny
positions (Fig. 3). These supports the ideathatsunflights areprobably important
forthermoregulation. By sunbasking insunspotsandthetree tops themales ob-
tainasufficientbody temperatureforactivitiesinsidetheirshady territories(MAY,
1976, 1977, 1991;McGEOCH &SAMWAYS, 1991). As I couldnot observe the
animals inthetree tops, I can not excludeactivities like mating or feeding when
they leavetheterritoriesforsunflights. Butfeedingis unlikely animportantstimu-
342 V.Clausnitzer
lationforthe frequent sun flights, as thereis alot ofpossible prey atthepools. I
havenever seenN. robertsi hunting or feeding atthepools,butotherspecies andI
suppose N. robertsihuntsinthemorning andafternoonhours.There seems to be
no reasontofeed exclusively inthetree tops during theterritorialtime,whichalso
supports thermoregulation as themain functionof thesun flights.
Perching has been regarded as an energy conserving act and to prepare
metabolically for flying (MAY, 1976;HEINRICH& CASEY, 1978). This prob-
ably applies toN. robertsias itshabitatare shadyrainforestpools (SHELLY, 1982).
Perching mayannouncetoothermalesthatthepondis already occupied (MOORE,
1987).To some extendthis interpretation may beafunction fortheperching be-
haviourperformed by maleN. robertsiastheterritorialmalesperch visible inthe
centreoftheirterritories.Furtherthepermanentpresenceintheterritoryexceptthe
sun flightsenables theterritorialmales to geta highpercentageoftherarely ap-
pearing females.Femalesandnon-territorialmalesonly appearirregularly forshort
timesattheponds. Especially thefemalesspendmostoftheiradultlivesinthetree
tops.As territorialmalesspendmostoftheday attheponds, they haveto conserve
energy formaintaining theirterritorialpossessions.
Interspecific andintraspecific flights are aresponse to thepres-
enceofotherdragonflies.Theassumption, thattheseflightsaresexually motivated
(e.g. PAJUNEN, 1964b;MOORE, 1952)doesnot apply to N. robertsi. The share
ofintraspecific flights inall flightactivities is only 10%and decreases duringthe
day(Fig.2).Thisfitstheobservationsthatterritorieshavetobedefendedmainly in
themorning. ALCOCK (1987) describesfor Paltothemislineatipes also areduc-
tionofintraspecific clashesintheroutineofa day.
Sexual flights are caused by females of N. robertsi, N. jonesi and
Tetrathemiscorduliformis (all females look andbehave very similarly). Only a
small numberofthese flights leadsto asuccessful mating, eitherbecause thefe-
malebelongs to another species or is unwilling. Thenumberofsexual-flights in-
creases over the day,but is not correlatedto anincreasing numberofmatings. I
thinkthattheappetenceformating increasesover the dayandalsothenumberof
femalesof T. corduliformis appearing atwater. Sexual flights depend onanexter-
nal stimulusinthe formofafemale.
The proximate reason forthein spe c t ion f 1i g hts is themovement ofa
possible mate. Itincludesotherdragonflies, insectsandevenasmallwater rivulet.
Theultimatereason fortheseflights is not easy toexplain - itmightbeofaggres-
sive or sexualnature. As Ihaveneverobserved the animalshunting or feeding in
theterritories, this cannot be regarded as apossible stimulus. The numberofin-
spection flights increases over the day (Fig. 2). Atthe same time thenumberof
inter- and intraspecific flights decreases, while the numberof sexual flights in-
creases. ThereforeI interpret theinspection flights as sexually stimulated.
Allflight activities discussed so farshow amoreor less distinct triggermecha-
nism, e.g.presenceofmales, females,movement ofotherobjects, shadinessofthe
Territorialityin Notiothemis mbertsi 343
perch. Moredifficultis theexplanation ofp at r o11 in g.Theseflightsseemtobe
spontaneousandindefinite(Tab. I) andIregardthemas unspecifiedincomparison
to inspection flights, but endogenous stimulatedby sexual andterritory-defence
motivation.
Patrolling isa commonbehaviourofterritorialmaledragonflies (e.g.DeBANO,
1993;HASSAN, 1978;PARR&PARR, 1974;WATANABE etal„ 1987),butsel-
domexplained. WATANABE etal.(1987) describe thisflightas ananalogue be-
haviourto theterritorialsongsofbirds.Inthe case ofN. robertsiIregardpatrolling
together withperching as the behaviours to demonstratethat thisterritory is al-
ready occupied.
Mostofthebehaviour the territorialmales ofN. robertsi show corresponds to
theirlongterritorialperiod, nonseasonality andscarcityoffemales.Itis anadoption
totheirhabitat- smallandshady rainforestponds.Otherspecies, whichbelongto
theTetratheminaeandliveinsimilarhabitats, show comparable territorialbehav-
iour and mating systems, e.g. Micromacromiacamerunica, Notiothemisjonesi,
Tetrathemiscorduliformis andT. camerunensis(e.g. LEMPERT, 1988;MILLER,
1993).
ACKNOWLEDGEMENTS
1ammost gratefultoMr WILBERFORCEOKEKAfor hishelpandhospitalityin theKakamega
ForestandtoDrANDREASMARTENSforvarious supportingideasand commentsand foraconsid-
erable amountoftime. I also wishtothankthe late Dr PETER MILLER for inspiringideas, Mr
GRAHAMVICKforthe determination ofsomespecies.ProfessorMIKEPARRfor valuablecriticism
onthe manuscript,my parents forfinancial support andhelpinthefieldandProfessor REINHARD
REMANEandProfessor GEORG RUPPELL, who madethisworkpossible.
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