Ecology and Sexual Selection in the Barking ( garrulus) Toby J Hibbitts University of the Witwatersrand, School of , Plant, and Envi ronmen ta l Sc iences, Pr iva te Bag 3, Wits 2050, Sou th Afr ica Sexual selection

• 5 mechanisms • I focus on endurance rivalry, contest competition, and mate choice Endurance rivalry

The most persistent males are the most successful breeders

Favours: males in the best body condition, or males which loose condition slowly. Contests

Fights between males for the best territories or access to females Mate choice

Mates chosen based on certain characteristics, i.e. display behaviour, colour, tail length, call. Signals

Animals use signals to avoid conflicts and attract mates

Signals used in contests are referred to as armaments andhd those use did in mate c hihoice as ornaments

Siggynals may also be broadcast throu gh different sensor y modalities (Auditory, olfactory, vision). Role of Ecology

• Without ecological information on a more in depth studies cannot be undertaken.

• KldfbdiKnowledge of breeding season, ma ting system and habitat preferences are necessary ftdiifor studies in sexua lltil selection. Study organism

• Why study the barking gecko? – Multiple multimodal signals – Unique in the degree of calling for a – Common – Relatively unstudied Calling gecko What is known? -Live in self constructed burrows (Haacke 1975) -Call at dusk (Haacke 1969) -Will defend against calling intruder (P. kochi; Polakow 1997) -Lay one egg clutches (Pianka and Huey 1978) -Ea t mostl y termit es b y vo lume (Pian ka an d Huey 1978) P. garrulus distribution

Molopo Nat. Res. Major Questions

• Report the ecology of the common barking gecko () diet , reprod ucti ve season, forag ing mo de, sexua l s ize dimorphism • What is the mating system? • Does olfaction plays a role in male refuge selti?lection? Objectives cont .

• How do males respond to playbacks of a known frequency and how do the throat patch and call relate to responses? • Are males that are active the longest have the highest reproductive success (Endurance rivalry)? • Wha t mal e c harac ter is tics corre la te w ith reproductive success? Ecology

• Sexual size dimorphism • Diet • RdtiReproductive season • Foraging mode

Hibbitts et al. 2005 Morphology

• I measured: svl , tail, head width, head depth, and trunk length. All except svl were size -adjusted. • I conducted t-tests on all morphological measurements. • The only significant result was size- adjus te d hea d w idth. Head width t = 1.98 p = 0.002 (n = 66f and 82m)

14.00 13.00 12.00 11.00 10.00 d Width 9.00 Hea 8.00 7.00 6.00 30.00 35.00 40.00 45.00 50.00 55.00 60.00 SVL Dietary raw data

N = 640 stomachs, 525 (82%) had food items, 115 (18%) empty

3086 prey items identified and 17 gecko shed skins. Methods

Prolate spheroid for testes and prey volume: V=4/3π(length/2)(width/2) Niche Breadth using Simpson’ s diversity measure: P. garrulus diet by prey number

1578 Isoptera (51%) 1100 Formicidae (36%) 191 Co leop tera (6%) All other groups (7%)

Niche Breadth 2. 5 P. garrulus diet by volume

5883.29 Isoptera (60%) 875.85 Formicidae (8.93%) 788.37 C o leop tera (8 .04%) All other prey (23.03%)

Niche Breadth 2. 60 Male vs. Female diet

No difference between sexes in prey 3 number eaten (χ2 = 3.62; P < 0.5). No correlation between prey size and HW while accounting for SVL (r = 0.099, P = 0440.44). No difference in the size of prey eaten by maldflles and females Testes volume and Egg length not significantly correlated with SVL

18

16 40 16

14 33 9 14

12 12 ) 3 10 10 m th (mm)th mm 8 8 58 6 6

Volume ( 12 Egg Leng 4 4 15 2 42 Inactive 2 48 0

0 012345678910111213Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month -2 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Foraging mode

• Conducted 11 ten minute observations of adult barking (6 male, 5 female), noted all movements and length of each move. • MPM = 0 . 4 ± 19(01.9 (0 - 21)2.1) • PTM = 4.6 ± 1.9 s (0 - 16.7)

(criterion of PTM < 10 for ambush foragers) Conclusions

• Male barking geckos have wider heads than females and the difference was not due to niche divergence • Barking geckos eat mainly termites and ants by number but volumetrically termites are most important • Peak reproduction occurs in September and ObibhOctober in both sexes • Barking geckos are classic ambush foragers Mating system

• What type of mating system? • Are males active before females (Protandry)? Methods

• Located ggyecko burrow in a 1.1 ha study area and marked each location and recorded the sex of each occupant. Burrows were monitored daily for a 67 day period from Sept to Nov 2004. • The following data was collected on all geckos captured: SVL, mass, sex, and throat patch size (if male). An attempt was made to record all calling males in the study area. Home range size Home range size

• Average HRS of 51 males – 10.4 ± 1.5 m2 (range = 3.1 to 53.0) • mean number overlapped = 0. 12 ± 0040.04 • mean percent overlap = 3.8 ± 1.7 • Correlations – HRS and SVL (r = 0.31, P = 0.02, n = 51) – HRS and freq (r = -0.24, P = 0.20, n = 31) – HRS and TPS (r = -0.13, P = 0.72, n = 49) Activity

70 Males Females 60 2 per. Mov. Avg. (Males) 2MA(Fl)2 per. Mov. Avg. (Females) 50

40 r of geckos ee 30

Numb 20

10

0 8/31 9/10 9/20 9/30 10/10 10/20 10/30 11/9 11/19 11/29 Date Activity cont

90

80

70 s

oo 60

50 Males

40 Females

30 Number of Geck

20

10

0 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 Days Conclusions

• Mating system is consistent with Polygyny – Males live in largely exclusive home ranges – Males aggressivel y defend their territor y – Males potentially breed with more than one female in a season • Males are active before females (Protandry) – Establish territories before females emerge – MlMales are rea dy to bree dbfd before fema le emergence Sexual selection

• Olfaction

• PlbktilPlayback trials

• Reproductive success Olfaction

• Do males avoid refuges scented by other males?

– A male was given the choice of a scented and unscented tile refuge – During 20 experiment 10 chose scented and 10 chose unscented

Hibbitts and Whiting 2005 Conclusions

Scent signals not present in barking geckos because: – Never observed to tongue flick – Calling likely signals presence for efficiently – Loose sandy substrate Playback trials

Multiple signals in barking geckos

Throat patch (visual) functions over short distances and in adequate light conditions

Call (auditory) functions over long distances

Contest - questions

• How do signals function in male-male interactions? • Is calling costly? Endurance rivalry - question • Do males which are more active have better reproductive success Mate c ho i ce - questi on

• What male characteristics best predict breeding success Signal correlations

5500 y = -62.829x + 7208.8

Call frequency (n = 74) correlated z) 2

HH r = 0.4952 with body size 5000 4500 2 (r = 0.50, F1,72 = 69.8, P < 0.001) 4000 nant frequency ( frequency nant ii 3500 Dom 3000 35 40 45 50 55 SVL (mm)

Throat patch size (n = 149) not correlated with body size

2 (r = 0.06, F1,120 = 7.13, P < 0.009) Playback trials

• We conducted playback trials to determine what gecko characteristics predicted behavioural responses Playback trials

• video Playback trials (n = 58)

• 3 main behaviours – Retreat into burrow – Call back – Charge • Multiple logistic regressions (SVL, condition, frequency, relative TPS) – Retreat – SVL (small) only significant character – Call back – None significant, condition close (0.06) – Charge – frequency (low) , relative TPS (small) only significant characters Playback trials

• Aggressiveness Rank – Ranked observed responses to playback trials from 0-5. – Did multiple regression with rank treated as continuous and SVL, condition, frequency, and relative TPS as independent variables – The model found that SVL (P = 0.01) and relative TPS (P = 0.04) were best indicators of aggressiveness Cost of calling

0.01

0.005

0

SVL vs weight loss day per

ee 30 35 40 45 50 55 -0.005

(gm) -0.01

-0.015

-0.02 y = -0.0008x + 0.0303 2 avg weight chang R = 0.3274 -0.025 SVL (mm)

No significant difference between geckos grouped as frequent and infrequent callers (P > 0.05)

Six males recaptured after greater than 50 days averaged weight loss of 16% (range 9 – 24%) of their body weight Reproductive success

Photo by David Laurencio Endurance rivalry

I tested whether male activity (males call when active in the breeding season) was higher in males who bred successfully .

No difference was found between the groups t2292,29 = 1.7, P = 0.34 Successful male characteristics

• Conducted multippgle logistic re gression with Bred as categorical dependent and SVL, HW, HD, TPS, and Frequency as independent variables. The morphological variables were corrected for byyyg size by using the residuals from regressions against SVL.

• SVL was the only significant indicator of breedingg( success (P = 0.01))g with larger males more likely to be successful breeders. Conclusions

• Call frequency is strongly correlated with SVL and therefore likely signals body size. • TPS was not correlated with morphological character, is a signal of aggressiveness • CllfCall frequency is lower an dTPSid TPS is sma ller in geckos which charge the playback and SVL is sma ller in ma les tha t re trea t from playback calls Conclusions

• Aggressive males are large and have small relative throat patches • Activity costly! – not correlated to calling • Activity is not a major fffactor influencing breeding success • Successfully breeding males were larger Acknowledgements

• We would like to thank the following people for help in the field and support at MlMolopo Nature Reserve: • Rachel Gallagher • Steven Gore (Formerly Park Warden at MNR) • Gerald and Inna Botha • David and Laura Laurencio • Kate Hodges • Ingrid Stirneman • We also thank Devi Stuart-Fox for statistical advice and the rest of the Whiting Lab for support • This project was funded by an NRF grant to Martin J. Whiting • Clearance was obtained for the study through the Wits University Animal Ethics Committee (2002/77/2a)