Gidgee Skink

Introduction

The Gidgee Skink (Egernia stokesii) is a shy species of spiny-tailed skink belonging to the large Egernia genus of Australian lizards. The species is named in honour of Admiral John Lort Stokes who served with Charles Darwin on the HMS Beagle and charted the Houtman Abrolhos Islands in Western Australia, where the type specimen was first collected. The common name is derived from the species' association with Gidgee Trees (Acacia species).

Identification

This medium-sized skink has a relatively short tail with keeled scales along its dorsal surface from the back of the neck down to the tip of the pointed tail. The legs are quite short, requiring the lizard to slide on its belly when it moves around. Its colour can vary from dark brown to a rusty colour, with scattered patches of paler scales.

Habitat

The species occurs in shrubland and open woodland, and often on rock outcrops. Groups of Gidgee Skinks will shelter between rocks, split trees and logs, and within hollows.

Distribution

The species has a widespread (though broken) distribution across semi-arid Australia, from far west New South Wales to the south-western interior of Western Australia. They are also known from several islands off the west coast of Western Australia.

Seasonality

The breeding season in the wild differs based on location; females in South Australia have been recorded giving birth between mid-summer and early autumn, however, a wild-caught female from Western Australia gave birth in mid-winter.

Feeding and diet

These omnivorous lizards feed predominately on vegetation such as fruit and leaves in the wild, as well as any invertebrate they can catch.

The captive diet for this species at the Australian Museum is provided in three feeds within a period of a week. These consist of a small feed of chopped vegetables on one day, a small serving of kangaroo mince on another day as well two cockroaches or crickets for the third feeding. The timing and order of the diet is changed around to simulate natural conditions and prevent stereotypical behaviour (where an animal will have predicable activity patterns and essentially be waiting to be fed). This food is supplemented with calcium and vitamin powder to ensure that a nutritionally balanced diet is provided.

Other behaviours and adaptations

The species tends to defecate in the same spot, a habit that leads to little piles of scats and probably derives from the set routines of animals living in the same place for long periods. This behaviour allows a group of lizards to concentrate its scent in one location away from where they shelter, making it difficult for predators to locate home sites.

Living in large social groups makes it easier to spot danger. When threatened this lizard will take cover in a hollow log, under bark or between rocks. If harassed further it will inhale air, making its body swell up - this increased size, combined with the spiky keeled scales, makes it difficult for a predator to dislodge the lizard from its hiding place.

Breeding behaviours

This species is highly monogamous with most males fathering only one litter. Females are sexually mature at a snout-vent length of 171 mm and have only one litter per season.

Not all mature females produce every season. In one study, 26 percent of the females did not reproduce in one year. Litter size ranges from 1-8. Gravid females experience contractions of the body and tail for up to 40 minutes prior to the beginning of birth. The young are born head first and each young takes from 26 to 73 seconds to be born. As little as 6 seconds may separate the birth of two skinks in the same litter and a single female can take 1-12 days to give birth to all her young.

Predators

Gidgee skinks fall prey to dingos, cats, foxes, birds of prey, monitors and snakes.

The species is often infected with the tick Amblyomma vikirri, a species that seems to be closely associated with rock outcrops. The larvae and nymphs of the tick tend to attach in the ears and on the digits whereas the adult ticks tend to seek the posterior part of the back and the tail.

Management

This species is protected in Australia and cannot be collected from the wild and a permit is required in most states and territories to keep this species in captivity. Please see the Resources for keeping live animals page and check with your local wildlife licensing agency.

References

Cogger, H. G. 2000. Reptiles and Amphibians of Australia. Reed New Holland, Sydney

Ehmann, H. 1992. Encyclopaedia of Australian Animals: Reptiles. Angus & Robertson. Pymble.

Fyfe, G. Skinks, Family Scincidae. From Swan, M. (ed.) 2008. Keeping and Breeding Australian Lizards. Mike Swan Herp Books. Lilydale.

Greer, A. E. 1990. The Biology and Evolution of Australian Lizards. Surrey Beatty & Sons.

Greer, A. E. 2006. Encyclopedia of Australian Reptiles – Scincidae. Australian Museum