Border Thick-tailed Gecko Underwoodisaurus sphyrurus - reject delisting of vulnerable species

NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to REJECT a proposal to remove the Border Thick-tailed Gecko Underwoodisaurus sphyrurus (Ogilby 1892) as a VULNERABLE SPECIES in Part 1 of Schedule 2 of the Act. Listing of Vulnerable species is provided for by Part 2 of the Act.

 

The Scientific Committee has found that:

 

1. After exhibition of a Preliminary Determination in May 2009 to delist the Border Thick-tailed Gecko as a Vulnerable species, information received from public submissions and associated re-examination of available information have led the Committee to conclude that there are insufficient data to support such a delisting.

 

2. The Border Thick-tailed Gecko Underwoodisaurus sphyrurus (Ogilby 1892) is a medium-sized gecko (up to 8 cm from snout to vent) that is mottled brown with bands of fine white raised dots. The tail is distinctively plump and knobbly, tapering to a fine tip with two broad and two narrow cream bands (Ehmann 1992; Cogger 2000; Wilson & Swann 2003; Swann et al. 2004). It is most similar to the Barking Gecko, U. milii, which is darker purple-brown with fine bands of yellow dots on the head and body. Many other geckos are similar in appearence, but either lack the bands of raised dots and the knobbly tail or have distinctive tail shapes.

 

3. The Border Thick-tailed Gecko occurs on the granite belt and other rock outcrops in rugged terrain of the NSW Northern Tablelands and North-west Slopes (New England Tableland, Nandewar and Brigalow Belt South Bioregions), extending over the Queensland border (c. 100 km) to Girraween National Park and west of Stanthorpe-Warwick. The number of populations is uncertain: 21 locations, possibly representing populations or subpopulations, were known prior to 2000 (Environment Australia SPRAT database, based on Cogger et al. 1993 and P. Spark unpublished data 2001). These include Durikai State Forest, Sundown National Park (NP), Girraween NP (all in Qld), east of Bonshaw, Bolivia Hill Travelling Stock Reserve, Torrington State Conservation Area, Emmaville rubbish tip, Severn River Nature Reserve (NR), Kings Plains NP, Copeton Waters State Park, Mt Kaputar NP, Single NP, Ironbark NR, Linton NR, Nandewar Range, Kelvin State Forest, Gunnedah vicinity, Moonbi Lookout, Attunga State Forest, Woolomin and Chaffey Dam. Since 2001, the following 14 locations have been added to the NSW Wildlife Atlas database: Meehi State Forest, Arakoola NR, Mole River, Gibraltar NR, Howell, Inverell, Bingara, Horton River, Barraba, ‘Bornhardtia’ (voluntary conservation area adjacent to Ironbark NR), Warrabah NP, Oxley Lookout (Tamworth), Currys Gap State Conservation Area, and Quipolly Dam area, near the town of Quirindi.

 

4. The Border Thick-tailed Gecko is most commonly found in undisturbed habitat remnants on rock outcrops and stony hills within eucalypt and cypress-pine open forest or woodland between 500 and 1100 m elevation. The Border Thick-tailed Gecko was formerly thought to be restricted to granitic substrates, but records from regenerating habitat on basalt and metasediment lower slopes and flats, i.e. more fertile and less rugged sites, suggest the gecko was once more widespread in vegetation types that have been cleared (P. Spark pers. comm. 07/06/08). Habitat preferences include areas with numerous logs and timber debris, and a sufficiently dense tree canopy to create a sparse grass/herb ground cover and abundant litter (P Spark unpublished data). Geckos shelter in well-shaded micro-sites, including under rocks and logs, under bark on standing trees, and commonly inside decomposing logs (notably old Rough-barked Apple, Angophora floribunda logs, which may be a moist drought refuge). The gecko is an insectivore, feeding primarily on insects and spiders.

 

5. No estimates of population size are available, even of sample densities, but there were 15 museum specimens in 1993 (Cogger et al. 1993) and there are now 83 NSW records of the species in the NSW Wildlife Atlas database. Frequency of encounter during targeted surveys is low, with typically only one animal found per site surveyed for several person-hours (P. Spark unpublished data). Its abundance was described as very sparse to sparse (Ehmann 1992) on the basis of limited data available at the time. More recently Border Thick-tailed Geckos were recorded in surveys of the Nandewar Western Regional Assessment where the species is described as occurring widely but at low densities (Andren in litt. 10/2009; Andren 2004).

 

6. The Border Thick-tailed Gecko’s known extent of occurrence is approximately 37 000 km2. The exact area of occupancy is uncertain, but applying a 2 x 2 km grid (as recommended by IUCN 2008) over the c. 55 discrete NSW sites (separated by more than 2 km) in the Wildlife Atlas database gives a calculated minimum area of occupancy of 220 km2. Given the low detectability of the species the actual area of occupancy is likely to be larger but unlikely to be greater than 1000 km2.

 

7. Although recent increases in survey effort and familiarity with the species have extended its known range by over 50 km southwards, the Border Thick-tailed Gecko is suspected to have been adversely affected in the past by clearing for agriculture, logging, and inundation of habitat by reservoirs (Cogger et al. 1993). Most sites occupied by the Border Thick-tailed Gecko are on skeletal midslope and ridge habitats that are of low agricultural value, but the more fertile sites remain vulnerable to clearing. At present, the main threats to the Border Thick-tailed Gecko are increasingly frequent fires, the presence of exotic predators, the expanding threat of invasive exotic grasses and the removal of fallen timber and bushrock. In particular, the decline of habitat quality due to invasion by dense stands of Coolatai Grass (Hyparrhenia hirta) may become a significant threat (P. Spark in litt. 06/2009). ‘Clearing of native vegetation’, 'Removal of dead wood and dead trees', 'Bushrock removal', 'Predation by the Feral Cat Felis catus (Linnaeus 1758)', ‘Predation by the European Red Fox Vulpes vulpes (Linnaeus 1758)’, ‘Invasion of native plant communities by exotic perennial grasses’, and ‘High frequency fire resulting in the disruption of life cycle processes in plants and animals and loss of vegetation structure and composition’, are listed as Key Threatening Processes in NSW under the Threatened Species Conservation Act 1995.

 

8. The Border Thick-tailed Gecko Underwoodisaurus sphyrurus (Ogilby 1892) is not eligible to be listed as an Endangered or Critically Endangered species.

 

9. The Border Thick-tailed Gecko Underwoodisaurus sphyrurus (Ogilby 1892) is eligible to be listed as a Vulnerable species as, in the opinion of the Scientific Committee, it is facing a high risk of extinction in New South Wales in the medium-term future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:

 

Clause 15

The geographic distribution of the species is estimated or inferred to be:

(c) moderately restricted,

and:

(d) a projected or continuing decline is observed, estimated or inferred in:

(ii) geographic distribution, habitat quality or diversity, or genetic diversity.

 

 

Dr Richard Major

Chairperson

Scientific Committee

 

Proposed Gazettal date: 20/08/10

Exhibition period: 20/08/10 – 15/10/10

 

References:

 

Andren MJ (2004) ‘Nandewar biodiversity surrogates: vertebrate fauna’. Report for the Resource and Conservation Assessment Council, NSW Western Regional Assessments. Department of Environment and Conservation, Coffs Harbour.

 

Cogger HG (2000) 'Reptiles and amphibians of Australia.' (Reed New Holland: Sydney)

 

Cogger HG, Cameron EE, Sadlier RA, Eggler P (1993) 'The action plan for Australian reptiles.' (Australian Nature Conservation Agency: Canberra)

 

Ehmann H (1992) 'Encyclopedia of Australian animals: Reptiles.' (Angus & Robertson: Sydney)

 

IUCN (2008) ‘Guidelines for using the IUCN Red List Categories and Criteria. Version 7.0.’ (Standards and Petitions Working Group of the IUCN Species Survival Commission Biodiversity Assessments Sub-committee: Switzerland). (http://intranet.iucn.org/webfiles/doc/SSC/RedList/RedListGuidelines.pdf).

 

Swann G, Shea G, Sadlier R (2004) 'A field guide to reptiles of New South Wales.' (Reed New Holland: Sydney)

 

Wilson S, Swann G (2003) 'A complete guide to reptiles of Australia.' (Reed New Holland: Sydney)

Page last updated: 28 February 2011