Threatened Species Strategy – Year 3 Priority Species Scorecard (2018) Central Rock-rat Zyzomys pedunculatus Key Findings The Central Rock-rat has experienced extreme declines in range and population size, due to predation by feral cats and extensive fires which can remove cover and reduce food availability across the species’ entire current range. Only ~650 individuals remain and a recent analysis ranked Central Rock-rats as the mammal taxon most likely to go extinct in the next 20 years. Recovery efforts have focused on landscape-scale feral cat and has contributed to the improved population trajectory for the species since 2015. Ongoing management of feral cats and fire will be important to prevent future declines. Photo: Perth Zoo Significant change in trajectory from 2005-15 to 2015-18? Yes, decline ongoing but at a slower rate. Priority future actions • More intensive fire management to limit incidence of extensive fires surrounding the rock-rat refuge sites. • Ongoing cat control around Central Rock-rat sites (eg. poison-baiting), including just after high rainfall periods, when cat predation pressure may be highest. • Additional translocations to predator-free sites (islands or mainland fenced exclosures). Full assessment information Background information 2018 population trajectory assessment 1. Conservation status and taxonomy 8. Expert elicitation for population trends 2. Conservation history and prospects 9. Immediate priorities from 2019 3. Past and current trends 10. Contributors 4. Key threats 11. Legislative documents 5. Past and current management 12. References 6. Support from the Australian Government 13. Citation 7. Measuring progress towards conservation The primary purpose of this scorecard is to assess progress against the year three targets outlined in the Australian Government’s Threatened Species Strategy, including estimating the change in population trajectory of 20 mammal species. It has been prepared by experts from the National Environmental Science Program’s Threatened Species Recovery Hub, with input from a number of taxon experts, a range of stakeholders and staff from the Office of the Threatened Species Commissioner, for the information of the Australian Government and is non-statutory. It has been informed by statutory planning documents that guide recovery of the species, such as Recovery Plans and/or Conservation Advices (see Section 11). The background information aims to provide context for estimation of progress in research and management (Section 7) and estimation of population size and trajectories (Section 8). 1 Information current to December 2018 Threatened Species Strategy – Year 3 Priority Species Scorecard (2018) 1. Conservation status and taxonomy Taxonomy: Conservation status 2018 No subspecies are recognised. There are EPBC Act Critically Endangered four other species of rock-rat in the NT Endangered Zyzomys genus. WA Critically Endangered 2. Conservation history and prospects The Central Rock-rat is a medium-sized rodent with a thick and furry tail. It mostly eats seeds of grasses and forbs, supplemented with leaves, stems and some invertebrates (Edwards 2013b; Nano et al. 2003). It is one of five species in the genus Zyzomys. Three of the species in the genus have experienced marked declines and are listed as nationally threatened. The Central Rock-rat is the only species confined to arid areas; all other species in the genus have distributions that are wholly or mostly tropical. The Central Rock-rat has been lost from over 95% of its pre-European distribution (McDonald et al. 2018) and its current Area of Occupancy (36 km2) is among the smallest of Australian mammals. Within its Area of Occupancy, it is found living in an area of less than 500 ha, spread across a handful of sites on the tops (>950 m) of quartzite ranges west of Alice Springs (McDonald et al. 2017b; McDonald et al. 2015b). These sites are characterised by shallow, gravelly soils and exposed, densely-creviced rocky outcrops. The vegetation is a mix of spinifex, forbs and low shrubs, with a sparse layer of taller shrubs and low trees (McDonald et al. 2015c). Although the refuge habitat is relatively narrow, Central Rock- rats are capable, at least during periods of population expansion, of living in a much broader range of habitats, from hilltops to scree-slopes and valley floors, tussock and hummock grasslands, shrublands and woodlands (Wurst 1995). Recent trends for the Central Rock-rat have been of continued decline. In the decade between the two most recent extensive rainfall events (2000-01 and 2010-11), the area occupied by the Central Rock-rat has declined by over 80% (TSSC 2018). Occupancy rates at sites monitored over the period 2015 to 2016 almost halved (McDonald et al. 2017b). A recent analysis of extinction risk across Australian mammal species ranked the Central Rock-rat as the taxon most likely to go extinct in the next 20 years (Geyle et al. 2018). A separate analysis of the conservation security of Australian mammal taxa that are susceptible to predation by cats and/or foxes concluded that the Central Rock-rat was the taxon most urgently in need of protection within a cat- and fox-free site (either an island, or a mainland fenced exclosure) (Legge et al. 2018). With support from the Australian Government, a trial of landscape-scale cat control was carried out by the Northern Territory government between 2015-18 around the refuge sites for the Central Rock-rat. Aerially-deployed Eradicat baits were effective at reducing cat density, and there was some indication of a positive response by the Central Rock-rat, although the program would need to continue for this to be confirmed (McDonald et al. 2017a). Translocation of the species to a site that is free from cats and foxes is a high priority management action. The current construction of a fenced exclosure at Newhaven Sanctuary (supported by the 2 Information current to December 2018 Threatened Species Strategy – Year 3 Priority Species Scorecard (2018) Australian Government) may offer a translocation site; islands off the coast of Western Australia should also be considered and have previously been proposed (Burbidge 1996). Captive breeding is being considered for this species, partly as insurance against its precarious status in the wild, and also as a step towards supporting a translocation to a cat-free site. Both translocation and captive breeding entail risks, because they involve removing animals from the wild which could compromise the persistence of that small wild population. In addition, earlier attempts to maintain a captive Central Rock-rat group (1996-2007) met with mixed success, and husbandry techniques will need revision (McDonald et al. 2017b). 3. Past and current trends The Central Rock-rat has disappeared from over 95% of its pre-European distribution. Before European settlement, its distribution extended from rocky areas in central Australia (Uluru north to the Granites) to the Cape Range in Western Australia. It was one of the most abundant species in cave deposit surveys at Cape Range and featured commonly in cave deposit surveys across central Western Australia and the Northern Territory (Baynes and Baird 1992; Baynes and Jones 1993; Baynes and McDowell 2010). Living specimens of the Central Rock-rat were collected from the Granites and the Davenport Ranges in the north, to the West MacDonnell Ranges and Illamurta in the south, from the 1890s until 1960, when an individual rock-rat was “caught raiding a stockman’s tuckerbox near Mt Liebig” (Cole 1999; McDonald et al. 2017b). After 1960, the Central Rock-rat was undetected for over three decades despite extensive trapping surveys in the Northern Territory and Western Australia (Gibson and Cole 1993; McDonald et al. 2017b) and was thought to be extinct (McDonald et al. 2017b; Wurst 1990). In 1996, a population was discovered near Ormiston Gorge, in Heavitree Range, in Tjoritja (West MacDonnell) National Park, by Australian Trust for Nature Volunteers (Cole 1999; McDonald et al. 2017b). Following this discovery, the Central Rock-rat was detected at multiple sites along a 60 km section of a quartzite ridge in the West MacDonnell Ranges between 1996 and 2002 (Cole 1999). However, subsequent trapping surveys between 2002-2012 in the West MacDonnells, including around Ormiston Gorge, failed to detect the rock-rat at any of the sites where it had been captured in the previous decade. However, the rock-rat was found at two new, isolated sites at the top of Mt Sonder (to the west) and Mt Giles (on the Chewings Range) (Edwards 2013a; McDonald et al. 2013). Another isolated population was found in 2013 near Mt Edward, 70 km west of Mt Sonder (McDonald et al. 2015a). Camera trapping in 2014 detected the species again at one site on the Heavitree Range. Subsequent surveys suggest that the Mt Sonder population may have since been extirpated (McDonald et al. 2017b). Thus, the Central Rock-rat is currently known to exist only in the Chewings Range (including Mt Giles) and the Heavitree Range, both in Tjoritja (West MacDonnell) National Park, and on Mt Edward to the west, in the Haast’s Bluff Aboriginal Land Trust (McDonald et al. 2017b). Estimating population trends for the Central Rock-rat following its contraction to the West MacDonnells is difficult because of the large fluctuations in population size, changes in survey location, and the pattern of population appearance and disappearance. The recent Conservation Advice (TSSC 2018) used changes in the area of occupancy between 2000-01 and 2010-11 (the two most recent periods of extensive rainfall) to infer the rate of population decline, and estimated this as at least 81%. 3 Information current to December 2018 Threatened Species Strategy – Year 3 Priority Species Scorecard (2018) Central Rock-rat populations have sometimes increased strongly after widespread rainfall events in central Australia (e.g. in 2000), suggesting that the species expands with rainfall-driven seeding pulses.