NOTES ON THE ECOLOGY AND NATURAL HISTORY OF THE RARELY RECORDED GEKKONID LIZARD HETERONOTIA BINOEI IN THE GREAT VICTORIA DESERT OF WESTERN AUSTRALIA

By ERIC R. PIANKA Integrative Biology, University of Texas at Austin Austin, Texas 78712 USA Email: [email protected]

ABSTRACT Ecological data on the uncommonly encountered terrestrial gecko Heteronotia binoei are presented and discussed. Although Heteronotia is widespread in Australia occurring in many different habitats, it is rarely found in semi- pristine desert habitats. Heteronotia is composed of a complex of both sexual and asexual populations which may help explain its rarity. Sex ratio is biased towards females. Heteronotia exploit burrows of other animals for shelter and daytime retreats. Compared to other species of desert lizards, Heteronotia is a dietary generalist with a relatively broad dietary niche. These geckos reproduce in the Austral spring and have fixed clutch sizes of two eggs. Relative clutch mass averaged 9.9%.

INTRODUCTION Heideman 1993). Asexuality appears to have arisen multiple is widespread Heteronotia binoei times: both bisexual and uni- in Australia (Cogger 1992) and sexual forms can occur in like most geckos, Heteronotia is sympatry (Fujita et al. 2007), nocturnal, but it can often be where they hybridize (Strasburg found in diurnal retreats such as and Kearney 2005). A population under objects in rubbish tips (the of this gecko in the Pilliga scrub first stop for many herpe- in New South Wales was studied tologists). However, it is seldom by mark and recapture by found in semi-pristine outback Bustard (1968) who found the desert habitats (Pianka 2014). geckos below bark at the base of This gecko is a species complex dead trees or stumps. He reported consisting of both sexual and data on movements, growth, tail parthenogenetic populations loss and regeneration as well as (Fujita and Moritz 2009, Moritz on diet. 1983, 1991a, 1991b, Moritz and

120 METHODS whether eggs were ovarian or oviductal was noted [some of During 11 separate expeditions to these data were summarized in the Great Victoria Desert (GVD) appendices in Pianka (1986)]. of Western Australia from 1966 Niche breadths were calculated through 2008, my assistants and I using the inverse of Simpson’s spent 41 months (1256 days) in (1949) index of diversity [D = 1/ Σp 2] the field primarily during i where p is the proportion of Austral springs collecting and i resource state i. studying lizards (Pianka 1969a,b, 1982, 1986, 1994, 1996; Pianka and Goodyear 2012). Extensive data RESULTS were gathered at ten major study areas in the GVD (for exact Sex Ratios and Presence of Males. locations, see Pianka 1986 and Among the 25 adult individuals Pianka and Goodyear 2012) as collected on the 8 study areas well as at other non-study sites with Heteronotia, six males were nearby. Lizards were collected by present at four of the eight areas any means possible using a wide (B 3 , E 1, N 1, and R 1) but only variety of different techniques females were found at the other including turning over rubbish four study areas (A 6, G 2, L 3, and and fallen logs, exhuming, grab- Y 3) (numbers represent number bing, shooting, eyeshine, body of individuals of a given sex). shine and pit trapping. Out of a Four other females were found total of more than 20,000 lizards, on sites with males. Thus overall only 66 individual Heteronotia sex ratio on the eight study areas binoei were encountered, 13 of is 6/25 or 0.24. Samples are too which were juveniles. This small to argue that no sexual species was found at 8 of the 10 forms were present on the four study areas and might well be sites without males. Among 28 present on the two other areas other adult specimens collected but was not encountered due to incidentally on 15 non-study small sample sizes. sites, six other males were also found, a sex ratio of 6/28 or We recorded air and body 0.214. Combining samples yields a temperatures, times of activity, significantly female-biased sex microhabitat, fresh snout-vent ratio of 12/53 = 0.226. length (SVL), tail length, and weight for as many lizards as Habitat and Microhabitats. possible. Stomach contents were Heteronotia exploit burrows of identified and prey volumes other animals for shelter and estimated for all lizards collected. daytime retreats. They are some- Reproductive condition was also times found while exhuming recorded: for males, lengths of burrows of Liopholis (formerly testes were measured; for females, Egernia) striata. They also dig egg sizes were measured and their own small burrows off to numbers were counted, and the sides of larger burrows such

121 as those dug by monitor lizards four were in litter beneath or rabbit warrens. Of 66 geckos, Marble Gum trees. all but two were found on desert Thermal Relations. Like all flats and sandplains, one was nocturnal geckos, Heteronotia are caught at the base/slope of a thermoconformers, with body sandridge and another was temperatures positively corre- captured on a sandridge crest. Six lated with ambient air tempera- individuals were dug up in tures (Figure 1). No statistical various burrows mostly those thermal difference exists be- dug by Liopholis. Of 24 indi- tween active geckos versus those viduals found active at night, found in diurnal retreats. Body one was at the mouth of such a temperatures of these geckos burrow, two were found emerg- tend to be slightly above ambi- ing at dusk from the mouth of a ent temperature especially when rabbit warren, two were in hol- they are cold. low termite mounds, one was Diet. are dietary about 7 cm above ground at the Heteronotia generalists, consuming a wide base of a termite mound, one was variety of arthropods, especially 60 cm above ground in a rock spiders, grasshoppers and crickets crevice, nine were out in the (Table 1). Based on these data, open, two were close to spinifex dietary niche breadth is 7.72. tussocks, two near bushes, and

Figure 1. Body temperatures plotted against ambient air temperature for 24 Heteronotia. Circles are active geckos at night whereas squares are those in diurnal retreats. The line represents body temperature equal to ambient air temperature.

122 Table 1. Summary of stomach contents of 66 Heteronotia.

Number Volume Proportion

Centipedes 1 0.05 0.020 Spiders 21 0.69 0.282 Scorpions 1 0.01 0.001 Ants 5 0.09 0.037 Wasps 1 0.01 0.004 Locustids 6 0.36 0.147 Thysanurans 2 0.02 0.008 Roaches 1 0.17 0.069 Mantids/Phasmids 2 0.05 0.020 Beetles 6 0.11 0.045 Termites 42 0.13 0.053 Hemipterans 9 0.13 0.053 Lepidopterans 2 0.14 0.057 Larvae 5 0.09 0.037 Other Insects 8 0.14 0.057 Vertebrates 4 0.18 0.074 Vegetation 1 0.04 0.016 Other Unidentified 1 0.05 0.02

Totals 119 2.46 1.00

Reproduction. Ten females had at 5 sites and only in very small either enlarged yolked ovarian numbers at other sites where this eggs or shelled eggs in their gecko was present. Only 19 oviducts from September to geckos were collected at ten January. All had clutches of two study areas over the course of eggs. Relative clutch mass (egg two years of field work. I won- volume over female fresh body dered how it could be a dietary weight) averaged 9.9% for three generalist and occur at most sites females with shelled eggs in their but still be so uncommon. Craig oviducts. Average snout vent Moritz’s discovery of partheno- length (SVL) of gravid females is genetic forms offered an answer 44.1 mm. Average SVL of 12 adult to this dilemma: an all female males is 46 mm. unisexual does not require males and females could persist at near vanishingly low densities. I DISCUSSION remain baffled about how this When I assembled data for my rare gecko manages to disperse so 1986 book, I was puzzled by the effectively across the vast desert landscape. rarity of Heteronotia — this species was present on 8 of my 10 Extensive pit trapping from 1989 study areas but only as singletons to 2008 (over 62,000 pit trap

123 days) at 3 study sites yielded only Texas at Austin, the Denton A. 22 additional specimens, con- Cooley Centennial Professorship firming the rarity of Heteronotia. in Zoology at The University of Texas at Austin, the US National Science Foundation, and the US ACKNOWLEDGEMENTS National Aeronautics and Space For companionship and assist- Administration. I also thank ance in the field, I thank R. staffs of the Department of Allen, D. Beaton, K. Beaton, D. Zoology at the University of Bennett, H. L. Dunlap, R. Western Australia, the Western Dybdahl, A. Frank, W. F. Giles, S. Australian Museum, the De- E. Goodyear, W. B. Jennings, D. R. partment of Conservation and King, F. Odendaal, D. J. Pearson, Land Management (CALM) in M. Peterson, G. A. Pianka, C. Kalgoorlie, and the Western Roscoe, W. Saunders, K. Smith, L. Australian Department of En- A. Smith, and G. G. Thompson. vironment and Conservation Others who contributed in (DEC). Lizards were collected various ways to this research under permits issued by CALM include J. Anderson, K. Aplin, S. and DEC with the approval of Argus, J. Banning, A. A. Burbidge, appropriate animal ethics com- M. A. Cowan, H. Gordon, M. mittees in Australia and the Grenadier, R. A. How, V. Johnson University of Texas. Specimens Dennison, G. A. Kaufman, I. are housed in the Los Angeles Kealley, A. R. Main, B. Maryan, N. County Museum of Natural Scade, and G. M. Storr. Stomach History and the Western Aus- contents were identified by M. E. tralian Museum. Egan, S. E. Goodyear, C. Harp, S. McMahon, T. D. Schultz, and V. REFERENCES Stringer. Undergraduate research assistants assisted with dissec- BUSTARD, H.R. 1968. The ecology tions and laboratory analyses. I of the Australian gecko thank editor John Dell for many Heteronotia binoei in northern suggestions that greatly im- New South Wales. Journal of proved this manuscript. Zoology 156: 483–497. This research was supported out COGGER, H.G. 1992. Reptiles and of my own pocket and by grants Amphibians of Australia, 5th ed. from the National Geographic Reed Books. 775 pp. Society, the John Simon FUJITA, M.K. and C. MORITZ. Guggenheim Memorial Foun- 2009. Origin and Evolution of dation, a senior Fulbright Parthenogenetic Genomes in Research Scholarship, the Au- Lizards: Current State and Future stralian-American Educational Directions. Cytogenetics and Foundation, the University Re- Genome Research 127: 261–272 search Institute of the Graduate FUJITA, M. K., J. L. BOORE, and C. School at The University of

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