Survey guidelines for Australia’s threatened reptiles

Airlie Island ctenotus

Ctenotus angusticeps

Summary information

Distribution: the species is so far only known from Airlie Island just offshore from Onslow, and Thangoo Station on Roebuck Bay south of Broome, Western Australia.
Habit and habitat: this species is terrestrial, surface-active. Found in Acacia shrubland, coastal spinifex and tussock grass (Airlie Island), and coastal samphire flats (Roebuck Bay).
Activity period: presumably year round. It is active late morning to afternoon in the temperate months of the year, gradually changing to early morning and probably late afternoon in the hotter months of the year.

Survey methods

The account by Browne-Cooper and Maryan (1990) indicates they observed 35 individuals over a two day period. By contrast, the account of Sadlier (1993) indicates the species was difficult to observe and accurately identify, and was only reliably recorded from captures made by pitfall trapping.

Detection of the species at a site is reliant upon positive identification. For most species in this genus sight records are in most instances unreliable, given that it is not unusual for several morphologically similar species of Ctenotus to occur in sympatry. Pitfalls have proved to be a reliable way of trapping species of Ctenotus. If the survey involves a targeted search for this species, a series of pitfall trap lines comprising six 10 litre buckets spread along a 15-metre fence would be adequate for detecting the species, although other pitfall arrangements could be trialled.

Similar species in range: the genus Ctenotus is the largest and arguably the most challenging group of Australian skinks to identify. There are likely to be several similarly sized and patterned species within the range of the Airlie Island ctenotus and unequivocal identification can be difficult. For this reason, collection of tissue samples is recommended.

Key references for Ctenotus angusticeps

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

Browne-Cooper, R. & Maryan, B. 1990. Observations of Ctenotus angusticeps (Scincidae) on Airlie Island. Herpetofauna 20(1): 1-2.

Sadlier, R.A. 1993. A range extension for the scincid lizard Ctenotus angusticeps of northwestern Australia. Herpetofauna 23(1): 7-8.

Arnhem Land egernia

Bellatorias obiri

Note: Until recently this species was considered part of the genus Egernia, with dual names in use: either E. arnhemensis (Sadlier 1990) or E. obiri (Wells & Wellington 1985). Bellatorias obiri is used here, as this is the name listed under the EPBC Act.

Summary information

Distribution: recorded only from the western edge of Arnhem Land in the vicinity of the East Alligator and South Alligator River drainages, Northern Territory.
Habit and habitat: found in the sandstone escarpment of the Arnhem Land Plateau. The original description of Egernia arnhemensis (Sadlier 1990: p.32) cites the species as having been observed in ‘thickly vegetated, wet, rocky gorges with numerous deep crevices’ the sites being ‘closed forest’ and ‘rocky crevice’ habitats, with individuals having been ‘observed active in the vicinity of deep crevices in the late afternoon’ and collected in small mammal traps set late in the day and checked early the following day.
Activity period: probably active for most of the year. Presumably diurnal, though published observations of this species active are few. The capture of this species in mammal traps, usually set late in the day and checked early the following day, indicates some level of nocturnal or crepuscular activity.

Survey methods

All available information suggests that trapping with mammal cage traps at appropriate sites is likely to be the most effective method for detecting this species. A research project which targeted the near relative, the Major skink Bellatorias frerei (Fuller et al. 2005), used Elliot traps baited with peanut butter, rolled oats and honey (the standard small mammal bait used in these traps). Trapping for the Arnhem Land egernia with Elliot traps might also be enhanced by the use of bait. Trapping could be supplemented by searching during the late afternoon hours for individuals sheltering in rock crevices or by distant observation with binoculars of likely areas near hiding places where active individuals might be seen.

Capture rates with mammal traps are low. Recent targeted surveys for the species caught only a single individual, and another was observed (cited as Armstrong & Dudley 2004 in DEWHA 2010).

Similar species in range: none. Sadlier (1990) provides diagnostic traits for differentiating the Arnhem Land egernia from its nearest congener, the Major skink Bellatorias frerei, from eastern Australia and southern New Guinea. The Arnhem Land egernia has more numerous midbody scale rows (44–48 vs 30–36), more numerous paravertebral scales (59–65 vs 44–56) and a lack of differentiation in colour between the dorsal and lateral surfaces in contrast to a variety of colour patterns in the Major skink, including dorsal and lateral differentiation and a distinct laterodorsal zone (Sadlier 1990).

Key references for Bellatorias arnhemensis:

Armstrong, M. & Dudley, A. 2004. The Arnhem Land egernia Egernia obiri in Kakadu National Park. Report to Parks Australia (North).

DEWHA. 2010. Bellatorias obiri in Species Profile and Threats Database, Australian Government Department of the Environment, Water, Heritage and the Arts, Canberra. Available from: www.environment.gov.au/sprat. Accessed 2010-01-19T09:36:20.

Fuller, S.J., Bull, C.M., Murray, K. & Spencer, R.J. 2005. Clustering of related individuals in a population of the Australian lizard, Egernia frerei. Molecular Ecology 14: 1207-1213.

Gardner, M. G., Hugall, A. F., Donnellan, S. C., Hutchinson, M. N., & Foster, R. 2008. Molecular systematics of social skinks: phylogeny and taxonomy of the Egernia group (Reptilia: Scincidae). Zoological Journal of the Linnean Society 154: 781-794.

Sadlier, R.A. 1990. A New Species of Scincid Lizard from Western Arnhemland, Northern Territory. The Beagle 7(2): 29-33.

Wells, R. & Wellington, C.R. 1985. A classification of the Amphibia and Reptilia of Australia. Australian Journal of Herpetology, Supplementary Series 1-61.