Image supplied by Mel Doherty Iramoo ©

Striped Legless Lizard

Delma Impar

D. impar has an elongate body form and an almost snake-like appearance. However, this physical similarity is less striking after a second glance, which reveals several characteristic legless lizard features. Delma impar has a fleshy tongue that is round not forked and an external ear opening, traits which are not shared by snakes. Furthermore, all legless lizards possess hind limbs, which are reduced to short, scaly flaps that lay neatly along the body at the base of the tail.

D. impar has a base colour of pale grey-brown with, as the common name suggests, a number of dark brown or blackish dorso-lateral and lateral longitidinal stripes which start from the neck and cover the length of the body and tail (Cogger 1992). These stripes often have a white edging. The dorsal surface of the head may be slightly darker than that of the body, whereas the ventrum is typically white (Coulson 1990), cream (Jenkins and Bartell 1980) or pink (Nunan, pers. obs.). In some individuals, the yellow of the infralabial and adjacent gular scales extends back to the tympanum.

Unlike the adults, D. impar hatchlings lack any longtitudunial body stripes. However, they do have a characteristic dark brown or black head. It is possible that such markings are intended to mimic those of snakes, such as the juvenile eastern brown snake (Greer 1989). This dark colouration fades with age.

Delma impar may grow to approximately 30 cm in length, with an average adult body weight of 4.1 g (Coulson 1990). The tail is surprisingly long, and may contribute up to two thirds of the total body length. In common with their nearest living relatives, the geckoes, pygopodids have a voice box and may emit a high pitched squeak when handled or distressed. What function this voice serves in the wild is unknown, though it may be used to startle predators, or as a form of communication during mating, courtship and aggressive encounters.

Image supplied by Mel Doherty Iramoo ©

Delma impar inhabitats lowland native grasslands, typically dominated by native tussock forming grass species. Such species include kangaroo grass (Themeda triandra) as well as spear grass (Stipa bigeniculata). Grassland areas dominated by introduced species of tussock forming grasses have also been known to support numbers of D. impar (Kukolic et al. 1994), although it is unclear as to whether such areas provide the species with suitable long term habitat.

Within Victoria, the native grassland habitat of the species typically occurs on deep cracking clay soils with volcanic rocks scattered about the surface. Cracks in the soil may be extensive in these areas and are considered important in providing shelter from fire and predators, as well as a place to lay eggs (DCNR 1995). Rocks are also commonly used as refuge.

Little is known on the reproductive parameters of D. impar however it is considered probable that the species ovulates during spring and ealy summer, followed by egglaying in mid summer. The eggs are characteristically elongate in shape. Each clutch contains two eggs, as with the geckoes, and takes five to eight weeks to hatch (DCNR 1995). The eggs are soft shelled and approximately 2 cm in length, swelling to approximately 3 cm in length while incubating.

No research has been undertaken into the age at which sexual maturity is reached, nor the longevity or survivorship of individuals. Lizards held in captivity have provided some information, surviving up to four years and eight months (ACT Parks and Conservation, unpublished data) However it is difficult to ascertain whether captive survival is indicative of that in the wild.

Delma impar individuals have the ability to drop their tail. The proportion of the tail which a lizard drops may vary from just the tip, to the entire tail up to the vent. Considering that a majority of the total body length consists of tail, in cases where the entire tail was dropped, only a small portion of the original lizard would remain. This may be considered as a useful tool for avoiding predation. Individuals that have lost their tail are obvious, as body stripes are only uniform and continous along the length of the body for individuals with their original tail.

Distribution Recordings

Image supplied by Museum Victoria ©

Delma impar feeds only on invertebrate prey and may be considered as a selective arthropod feeder (Nunan 1995). While the predominant prey types of the species in Victoria were found to be crickets and noctuid moth larvae (Wainer 1992), spiders were found to be the predominant prey type within the ACT (Nunan 1995). Wolf spiders (Lycosidae) are the most common spider family consumed while jumping spiders (Salticidae) also occurr. Other main prey types of the species include cockroaches and grasshoppers, with the occassional occurrence of beetles, flies and ants within the diet (Nunan 1995).

Native temperate grasslands are one of the most endangered ecosystems in Australia (McDougall and Kirkpatrick 1994) with lowland native grassland now only remaining as isolated remnants throughout the country (Sharp 1994). Preferred grassland habitat of D. impar is generally flat and relatively treeless, making such areas highly suitable for development and agriculture. Within the ACT, the plains which are now extensively occupied by the urban development of Canberra once supported treeless grasslands (Osborne et. al. 1994) which were most likely inhabited by D. impar. Such losses of suitable habitat remain the greatest threat to the survival of this species, resulting in local extinctions from historically occupied areas.

Further threats to the species are associated with the fragmetation of grassland areas and their modification. Contributing factors include ploughing, the application of fertiliser, pasture improvement, grazing, cropping and the invasion of exotic species (Delma Working Group 1994). Considering the susceptability of grassland to fire, when situated close to urban areas, and the small size and isolation of many grasslands supporting D. impar, fire also poses a serious threat to the species. It is thought that individuals may burrow into the soil, retreat into cracks, or shelter within tussocks or litter during fire. However this may only be possible if the fire is cool enough to leave some vegetation unburnt or that the soil conditions are dry enough to provide cracks.

Little is known on the extent and impacts of predation upon D. impar. However, the encroachment of urban development would most certainly place more predatory pressure on the species. Powerlines and poles may provide increased perching or surveillance opportunites for birds of prey while urban development would introduce more cats into the area (Delma Working Group 1994) which may also prey upon the species.

The above information was sourced from:The Institute for Applied Ecology, University of Canberra