Islands in the sky: sampling the fauna of Coolah Tops

Situated between the western edge of the Hunter Valley and the Liverpool Plains, in central western New South Wales, Coolah Tops is an island of tall open forest in a sea of cleared agricultural land. It is also an island in the sky, a basalt plateau that rises to over 1000 m, and so is cooler and wetter than the surrounding lowlands. These features also make it an interesting site where eastern and western faunas mingle. Several species, such as the Greater Glider, Brown Antechinus and Delicate Sunskink, more typical of the moist forests of the Great Dividing Range are near the western limit of their range at Coolah Tops. The Tops also has significant areas of unlogged old growth eucalypt forest containing an abundance of the tree hollows that are so important to much of Australian forest fauna.

However, despite its reported high biodiversity and biogeographical interest, Coolah Tops and the surrounding area is poorly represented in the AM’s natural history collection. To try and rectify this, from the 7th-14th May 2018, staff from the Museum’s Mammal and Herpetology (reptile and amphibians) sections visited the area to survey and sample its fauna.

Despite the very dry conditions, a pleasing diversity of native mammals were observed. Red-necked Wallabies (Notamacropus rufogriseus), Swamp Wallabies (Wallabia bicolor), Eastern Grey Kangaroos (Macropus giganteus) and Common Wombats (Vombatus ursinus) were regularly sighted feeding in the late afternoon and throughout the night, making the most of the limited grassy patches. However, the presence of the introduced disease, sarcoptic mange, on several individual wombats is a cause for concern, as was the regular sighting of introduced Fallow Deer and feral pigs. At night, at least four possum species were observed, including high densities of Greater Gliders (Petauroides volans), as well as Eastern Ringtail Possums (Pseudocheirus peregrinus), Sugar Gliders (Petaurus breviceps) and a single Common Brush-tail Possum (Trichosurus vulpecula). In addition, seven Brown Antechinus (Antechinus stuartii), diminutive (~8 g) but ferocious carnivorous marsupials, were captured. The lack of captures of native Bush Rats (Rattus fuscipes) remains curious as this species is typically highly abundant in similar habitats to the east.

The highlight, for the mammologists, was documenting the presence of nine microbat species (6-26 g) using both harp traps, as well as from recordings of their species-specific echo-location calls on electronic bat detectors. Amongst these were two listed threatened species, the Large-eared Pied Bat (Chalinolobus dwyeri) and the Eastern Falsistrelle (Falsistrellus tasmaniensis). Documenting the continued presence of the Large-eared Pied Bat at Coolah Tops, where it was first recorded in 1993, was especially significant. This handsome species is poorly understood and has a limited distribution in NSW and Qld. It is rarely captured in harp traps but three were trapped at different sites during the current survey and echo-location calls were also frequently detected.

Interestingly, most captures of microbats (70%) were of just 2 species, the Large Forest Bat (Vespadelus darlingtoni) and the Chocolate Wattled Bat (Chalinolobus morio). Most bats captured (82%) were adult males. Exactly why is not clear because the basic ecology of these species is little known, but possibilities include altitudinal or spatial segregation of sexes at this time of year; chance proximity to predominantly male roost sites or increased male activity during the mating season.

Cold weather over the week kept reptile activity to a minimum, and meant the team targeted its efforts on searching for reptiles that were sheltering from the cold. Survey efforts were focused towards areas with good rock cover, and rocky outcrops and still managed to detect a good diversity of the expected reptile species. The most common reptiles were cold-tolerant skinks such as the Eastern Three-toed Slider (Hemiergis talbingoensis) and Weasel Skink (Saproscincus mustelinus) found on the plateau. Less commonly encountered in the plateau Snow Gum forest were Sunskinks (Lampropholis delicata and Lampropholis caligula), most interesting because these skinks are often the most abundant and dominant species in forests further east. Several species were found only in larger rocky outcrops with deep cracking boulders, including Cunningham’s Skink (Egernia cunninghami) and the Tree Skink (Egernia striolata). These rock-living Egernia and the Sunskinks found at Coolah brought much excitement to the herpetology team. While these species were previously known to occur at Coolah Tops, the area is an outlier in their range, and these populations may be isolated from other populations. Previously a lack of samples of any of these species from Coolah Tops had meant no study had been conducted assessing this isolation or whether these may even represent different species, making this survey a fantastic opportunity to do just that!

Overall, we sampled 14 different mammal and 9 reptile species providing material that has significantly improved our documentation of the regions fauna, as well as facilitate ongoing taxonomic and biogeographical research. The team hopes to return later in the year when conditions are warmer and hopefully not as dry.

Mark Eldridge, Stephen Mahony, Sandy Ingleby, Harry Parnaby, Anja Divljan
Australian Museum Research Institute

Acknowledgements
We are grateful to Mrs Mary Holt for supporting this project through a donation to the Australian Museum Foundation. Thanks also to Michael Murphy (NSW NPWS) for his assistance, advice and support.