Reintroducing the Dingo: the Risk of Dingo Predation to Threatened Vertebrates of Western New South Wales

CSIRO PUBLISHING Wildlife Research http://dx.doi.org/10.1071/WR11128 Reintroducing the dingo: the risk of dingo predation to threatened vertebrates of western New South Wales B. L. Allen A,C and P. J. S. Fleming B AThe University of Queensland, School of Animal Studies, Gatton, Qld 4343, Australia. BVertebrate Pest Research Unit, NSW Department of Primary Industries, Orange Agricultural Institute, Forest Road, Orange, NSW 2800, Australia. CCorresponding author. Present address: Vertebrate Pest Research Unit, NSW Department of Primary Industries, Sulfide Street, Broken Hill, NSW 2880, Australia. Email: [email protected] Abstract Context. The reintroduction of dingoes into sheep-grazing areas south-east of the dingo barrier fence has been suggested as a mechanism to suppress fox and feral-cat impacts. Using the Western Division of New South Wales as a case study, Dickman et al. (2009) recently assessed the risk of fox and cat predation to extant threatened species and concluded that reintroducing dingoes into the area would have positive effects for most of the threatened vertebrates there, aiding their recovery through trophic cascade effects. However, they did not formally assess the risk of dingo predation to the same threatened species. Aims. To assess the risk of dingo predation to the extant and locally extinct threatened vertebrates of western New South Wales using methods amenable to comparison with Dickman et al. (2009). Methods. The predation-risk assessment method used in Dickman et al. (2009) for foxes and cats was applied here to dingoes, with minor modification to accommodate the dietary differences of dingoes. This method is based on six independent biological attributes, primarily reflective of potential vulnerability characteristics of the prey. Individual- attribute scores were used to derive an overall risk score. Key results. Up to 75 (94%) of the 80 extant species were predicted to be at risk of dingo predation (71% at high risk) regardless of any effect dingoes might have on foxes or cats. Up to 17 of the 21 (81%) locally extinct species were predicted to be at high risk of dingo predation using this approach. The re-establishment of even low-density dingo populations may have negative effects on at least 22% of extant threatened vertebrates. Conclusions. The generic risk-assessment method was insensitive, and experienced difficulty in describing the true nature of canid predation risk. Despite this weakness, however, it is clear that several threatened vertebrates are susceptible to dingo predation. Prior to the re-establishment of dingoes, we recommend that dingo predation risks to all vertebrates (threatened or otherwise) be assessed using more sensitive and descriptive techniques, and we strongly caution against the positive management of dingoes under current ecological conditions. Implications. The results of this study imply that dingoes present similar levels of direct risk to threatened species as foxes and feral cats, and dingo predation of threatened species should be formally considered in any proposal encouraging dingo populations in western New South Wales. Additional keywords: apex predator, Canis lupus dingo, mesopredator suppression, predation-risk assessment, reintroduction, threatened fauna. Received 20 July 2011, accepted 8 November 2011, published online 30 January 2012 Introduction process termed ‘mesopredator release’ (Crooks and Soulé 1999). The biodiversity benefits of maintaining or restoring populations This has led to the restoration of grey wolves (Canis lupus lupus), of apex mammalian predators has been the subject of much brown bears (Ursus arctos) and lynx (Lynx lynx) into parts of discussion (Ray et al. 2005; Hayward and Somers 2009). Europe and North America (Merrill and Mech 2000; Trouwborst Anthropogenic removal of apex predators is perceived to 2010), and lions (Panthera leo), leopards (P. pardus) and other cause the ascent of mesopredator populations (Prugh et al. predators in southern Africa (Hayward and Somers 2009). 2009) and consequent negative changes in faunal and floral Repopulation of large predators has been facilitated by active biodiversity (Roemer et al. 2009; Estes et al. 2011) through a reintroductions, dispersal following reintroductions, and natural Journal compilation Ó CSIRO 2012 www.publish.csiro.au/journals/wr B Wildlife Research B. L. Allen and P. J. S. Fleming recolonisation associated with reduced human depredation Dickman et al.(2009: p. 258) concluded that reintroducing (Hayward and Somers 2009; Randi 2011). dingoes into that area would have ‘positive effects for most of Recently, the potential consequences of mesopredator the threatened vertebrates that currently occur there, and would release on predator–prey interactions in Australia have also improve conditions for restoring many others that have become been raised (e.g. Robley et al. 2004; Glen and Dickman 2005; locally extinct’. In total, up to 70 species were predicted to benefit Glen et al. 2007a). These reviews have indicated that dingoes from the suppression of foxes and cats by dingoes, with a further (Canis lupus dingo and other free-roaming Canis species) are 21 that could be successfully reintroduced along with the dingo a strongly interactive species, and although formerly exotic (Dickman et al. 2009). The direct predation risks of dingoes to mesopredators themselves (Johnson 2006; Fleming et al., these same species were not critically assessed in Dickman et al. in press), they have assumed apex predator status since the (2009). However, the authors did indicate that ‘four or five mainland extinction of the larger thylacine (Thylacinus large-bodied species’ may be eaten by dingoes (e.g. southern cynocephalus) which occurred within a few hundred years hairy-nosed wombats, Lasiorhinus latifrons). They postulated after dingoes were introduced (Corbett 2001b; Johnson and that because these four or five species were sympatric with Wroe 2003). Dingoes exert this status over other alien dingoes before European settlement, it was ‘unlikely that any mesopredators, such as foxes (Vulpes vulpes) and feral cats impact of dingoes on them would exceed that of foxes and cats (Felis catus), which were later introduced to Australia by under current conditions’ (Dickman et al. 2009: p. 258). Europeans (Rolls 1969; Abbott 2002). Applying trophic- Although dingoes do prey on large species (e.g. Marsack and cascade and mesopredator-release theory to an Australian Campbell 1990; Thomson 1992), dingoes are also efficient context, the general premise is that dingoes will exclude, limit, predators of small and medium-sized species, especially in arid regulate or suppress foxes and/or cats and thereby protect faunal areas (e.g. Corbett and Newsome 1987; Pavey et al. 2008; biodiversity from fox and/or cat predation (e.g. Letnic et al. Cupples et al. 2011; Newsome 2011). Thus, dingoes are 2009a; Wallach et al. 2009a; Carwardine et al. 2011). If this known to consume many of the same species they are also holds true, then the positive management of dingoes might assumed to protect. Summarising the prey remains found in provide indirect benefits to biodiversity. At present, however, 12 802 scats and stomachs from multiple dingo-diet studies multiple methodological shortcomings mean that only weak conducted in a variety of bioregions across Australia up to inferences (censu Platt 1964; MacKenzie et al. 2006) can be 2001, Corbett (2001b) reported that 72% of dietary items from drawn from most studies claiming support for the beneficial roles all bioregions are mammals, and 80% of those are of dingoes to native fauna (see Allen (2011), Allen et al.(2011b), small–medium-sized (<15 kg). Small–medium-sized mammals but see also Letnic et al.( 2011a), Allen et al.(2011a)). Because could therefore be considered preferred prey in all bioregions ‘weak inference mistaken for strong inference can be ruinously except the Fortescue River region of Western Australia, where dangerous’ (Caughley and Sinclair 1994: p. 230), more careful small–medium-sized prey were largely unavailable (see consideration of the ecological niches of dingoes and other free- Thomson 1992). Of the smallest species eaten, insects, reptiles roaming dogs in Australia is required before their positive and birds were present in dingo diets from most regions (Corbett management (Fleming et al., in press). 2001b). In line with the results of Paltridge (2002, n = 75 dingo Predation of Australia’s vertebrate fauna by introduced scats), Newsome (2011) showed that larger blue-tongued skinks predators has been a commonly identified cause of species (Tiliqua multifasciata, ~400 g), desert mice (Pseudomysdesertor, declines (e.g. Smith et al. 1994; Dickman 1996; Smith and 25 g), and unidentified small skinks were the three single most Quin 1996; McKenzie et al. 2007). Threat-abatement plans for frequently occurring live prey in dingo diets from 1907 dingo prevention of extinction by introduced predators have been scats collected over 2 years from the Tanami Desert (23%, 17% developed (e.g. DEWHA 2008a, 2008b). However, threat- and 14% occurrence respectively), with dingoes considered to mitigation actions also require assessment of their relative present signi ficant risks to local populations of these species. All risks before implementation (IUCNSSC 1995). Given the major dingo-diet studies from central Australia therefore report pervasiveness of threats from introduced predators and the rodents and reptiles (and rabbits, Oryctolagus cuniculus) to be the limited

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