Survey guidelines for Australia’s threatened reptiles

Collared delma

Delma torquata

Summary information

Distribution: most records are from south-east Queensland, in the western suburbs of Brisbane and inland to the Bunya Mountains, with outlying records from Ulam, and more recently, the Blackdown Tableland and Western Creek State Forest near Millmerran (Kluge 1974; Hines et al. 2000) west to stock routes between Roma and Mitchell (DERM unpubl. data). The Millmerran locality is only approximately 70 kilometres north of the NSW border, and it is possible that the species’ distribution extends into NSW.
Habit and habitat: the majority of records are from woodland sites, including open dry eucalypt woodland dominated by narrow-leaved ironbark Eucalyptus crebra, E. intermedia and E. maculata, and an understorey of grasses and creeping lantana Lantana montevidensis on stony soils or rocky ridges (Porter 1998). In the Bunya Mountains, the species inhabits forest red gum E. tereticornis woodland on dark cracking clays, while at Western Creek State Forest, it inhabits brigalow (Acacia harpophylla) and belah (Casuarina cristata) forest with wilga (Geijera parviflora) midstorey on fine grey cracking clay soils (Hines et al. 2000). The most westerly records are all from alluvial poplar box (Eucalyptus populnea) with no rock content (DERM unpubl. data).

Collared delmas have mostly been found under stones or coarse woody debris on soil, sometimes in association with termite nests, but have also been observed moving through low grass (Porter 1998). The type specimen was dug from soil (Kluge 1974), leading to speculation that the species was fossorial. Recent records have been hand-raked from fine flood-washed humus and debris and from the surface soil directly under leaf litter and from within thick grass tussocks (DERM unpubl. data). Some individuals were found sheltering in termite holes when disturbed (Porter 1998). They are mostly active from October to February but can be found year-round, except for winter months. There is some suggestion that the species may be grazing-sensitive, as all Brigalow Belt records are from ungrazed or rarely grazed areas (DERM unpubl. data).

Activity period: pitfall trap and sight records suggest that the species is diurnal (Porter 1998). The same study, which conducted pitfall trapping for two weeks over every eight-week period during one year, only trapped individuals between October and February, with four of six captures in December, suggesting that activity was greatest during this period. However, animals were able to be located under rocks throughout the year, and were usually active when disturbed beneath the rocks (Porter 1998), suggesting at least limited activity throughout the year. In the western part of the distribution, detectability seems to be impacted by soil moisture, suggesting they are relatively inactive or inhabit hard-to-search refugia during dry times.

Survey methods

Most early records of this species were collected serendipitously. A single study has been undertaken into the ecology of this species, using a combination of hand-searching under rocks and pitfall trapping (Porter 1998).

Pitfall trapping proved to be less effective than turning rocks in locating the species, with only six captures during the 12 months of the study, all from the period October to February. The study used 20 4-litre plastic buckets, arranged in lines of five buckets 1 metre apart, and bridged by 20 centimetre high aluminium mesh drift fences. Capture rate of the pitfall trap array was 0.306 animals per 100 trap nights, comparable to studies of the related striped legless lizard Delma impar.

Individuals were collected by hand from under rocks on soil throughout the year, at a rate of approximately one lizard per 150–200 rocks turned (or one lizard per 1.75 hours of searching). Porter observed a short-term effect of rock turning on lizard captures, with few captures at sites disturbed by previous rock-turning within the previous three months, although this effect appeared to be temporary, with normal recapture rates at such sites at the end of the study.

Similarly, of collared delma reported by Hines and colleagues (2000) and DERM (unpubl. data 2010) over surveys of numerous sites, two were pitfall trapped, while 20 were collected by hand.

Consequently it is recommended that appropriate survey methods for this species be one-off hand searches (including raking through leaf litter) in appropriate habitats, together with pitfall trapping during late spring to summer. A series of pitfall trap lines comprising six 4–10 litre buckets and funnel traps spread along a 15 metre fence would be an appropriate trap design.
Similar species in range: there are several small to medium-sized Delma species within the range of the collared delma: D. inornata, D. plebeia and D. tincta. The collared delma may be difficult to distinguish from juveniles of these species, particularly by the inexperienced surveyor, except with a hand lens or microscopic facilities. The collared delma has dark marbling on the throat (lacking in D. inornata and D. tincta), dark markings separated by narrow pale bands on the top of the head and neck (lacking in D. inornata, and without the pale bands in D. plebeia), a greyish belly (pale in D. inornata, D. plebeia and D. tincta), and only two preanal scales (three in D. inornata and D. tincta).

The collared delma is similar in body shape and degree of limblessness to several burrowing skink species, but all lack the characteristic head markings of the collared delma.

Key references for Delma torquata

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

Hines, B.M., Hannah, D., Venz, M. & Eyre, T. 2000. New distribution and habitat data for the vulnerable pygopodid, Delma torquata (Kluge 1974). Memoirs of the Queensland Museum 45(2): 391-393.

Kluge, A.G. 1974. Taxonomic revision of the lizard family Pygopodidae. Miscellaneous Publications of the Museum of Zoology, University of Michigan (147): vi. 221 pp.

Porter, R. 1998. Observations on a large population of the vulnerable pygopodid, Delma torquata. Memoirs of the Queensland Museum 42(2): 565-572.