124 J. L. Silcock et al.


investigated (Gordon et al., 1978). During five visits to the region during 1973–1974, five animals were seen and dung was recorded on three properties north of Adavale. Surveys at the locations of reported sightings in the Ennis- killen, Grey and McGregor ranges failed to detect the taxon, and the property owners from the type locality at Terrachie and nearby Mount Canaway stated that rock-wallabies had not been seen since the 1960s (Gordon et al., 1978). The study by Gordon et al. (1978) generated concern for


the long-term persistence of the yellow-footed rock-wallaby in Queensland (Briscoe et al., 1982;Archer etal., 1985)and prompted surveys to ascertain the distribution, abundance and habitat of what was by then recognized as a subspecies of P. xanthopus endemic to Queensland (Gordon et al., 1993;Eldridge, 1997). During 1973–1987, Petrogale xanthopus celeris was recorded at 44 sites north and north-west of Adavale, but the subspecies was considered vulnerable to extinction because of property development and competition from sympatric herbivores, notably feral goats Capra hircus and the common wallaroo Osphranter robustus (Gordon et al., 1993). Subsequent decades saw increases in goat and common wallaroo populations (Pople & Grigg, 2001;Pople & Froese, 2012) and clearing of the fertile Acacia-dominated valleysbetween therangesineastern partsofthe distribution of P. xanthopus celeris (Gordon et al., 1993). At 6–12 kg (Eldridge, 2023), adult yellow-footed rock-


wallabies are outside the preferred prey weight range of the red fox Vulpes vulpes (Saunders et al., 1995), but their joeys have a short pouch life and individuals are vulnerable to pre- dation as juveniles and subadults (Sharp et al., 2014). Feral cats Felis catus also predate juveniles in some rock-wallaby populations (Spencer, 1991; Read et al., 2018). Competition with goats for forage and habitat has been implicated in declines and could be linked to fox predation by forcing yellow-footed rock-wallabies to forage in suboptimal open habitats where predation is more likely (Hayward et al., 2011). The southern subspecies Petrogale xanthopus xantho- pus has declined throughout its range in New South Wales (Lethbridge & Alexander, 2008; Sharp et al., 2014)and South Australia (Copley, 1983) because of historical hunting for skins, predation by foxes, habitat modification from pastoral activities and competition with introduced herbi- vores. Intensive threat management has led to stabilization and recovery of at least some southern populations, and the most recent assessment for The Action Plan for Australian Mammals 2012 categorized this subspecies as Near Threa- tened [Conservation Dependent] (Woinarski et al., 2014). At the species level, P. xanthopus is categorized as Near Threatened on the IUCN Red List (Copley et al., 2016). In contrast, there has been little targeted management of


P. xanthopus celeris, and the subspecies is inferred to be undergoing continuing decline because of habitat degrada- tion and predation (Woinarski et al., 2014). Its categoriza- tion as Vulnerable under the Commonwealth Environment


Protection and Biodiversity Conservation Act 1999 within the last decade (Threatened Species Scientific Committee, 2016) reflects these concerns. Most published information on the subspecies comes from life history, population dy- namics and dietary studies on colonies at Idalia National Park (Sharp, 2009, 2011) and Lisburne Station (Allen, 2001) as well as genetic studies across a small number of sub- populations (Pope et al., 1996;Smith et al., 2023). The yellow- footed rock-wallaby is cryptic, occurs in remote and rugged mountain ranges and fluctuates in abundance relative to rainfall (Sharp & Norton, 2000; Lethbridge & Alexander, 2008; Sharp &McCallum, 2015), rendering an accurate con- servation assessment impossible without repeated surveys across its entire distribution. Here we present the results of surveys undertaken throughout the range of P. xanthopus celeris during 2010–2015 and 2020–2023, including revisits to historical sites and assessments of areas of potentially suitable habitat selected using satellite imagery and local knowledge. We compare our results with the 1970s–1980s surveys, to examine population trends over the past 50 years in relation to threats, thereby facilitating a more accurate conservation assessment to guide management of P. xanthopus celeris.


Study area


The Grey Range, together with smaller connected range systems, is composed of Tertiary sandstone and stretches 700 km through inland eastern Australia, from north-western New South Wales to central-western Queensland. Petrogale xanthopus celeris occurs in the northern part of the system, encompassing the Grey, Gowan, Yanyang, Macedon, Cheviot, Wallaroo, Edinburgh and Ambathala ranges, with outlying records from the south (McGregor and Coleman ranges near Eromanga and Thargomindah, 200 km south of Quilpie) and north-east (Warrego and Enniskillen ranges; Fig. 1). Its core distribution is in the central north of this area where the residual land system is broadest, stretching over 100 km fromeast to west. Elevations fall from450maltitude on table- lands in the north-east to just over 200 m in the south. The climate is semi-arid, with mean annual rainfall decreasing from 485mm in the north-east to 250 mm in the south-west of the study area. Most rain falls during December–March. Summer temperatures are hot,with daily maxima throughout December–February averaging 35 °C and regularly exceeding 40 °C, whereas short winters are characterized by cold nights (often falling below 0 °C) and warm days. Seven major vegetation communities occur in the Grey


Range and associated ranges (Silcock & Fensham, 2014). Gorges and boulder fields form along the edges of escarp- ments, providing complex, sheltered diurnal habitats, which are preferred by P. xanthopus celeris (Gordon et al., 1993). Acaciawoodlands and shrublands dominate the slopes, table- lands and valleys. The valleys in the north-east have been


Oryx, 2025, 59(1), 123–135 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605324000760


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