Long-term benefits and short-term costs: small vertebrate responses to predator exclusion and native mammal reintroductions in south-western New South Wales, Australia

Abstract

ContextThe success of conservation fences at protecting reintroduced populations of threatened mammals from introduced predators has prompted an increase in the number and extent of fenced exclosures. Excluding introduced species from within conservation fences could also benefit components of insitu faunal assemblages that are prey for introduced predators, such as reptiles and small mammals. Conversely, reintroduced mammals may compete with smaller mammals and reptiles for resources, or even prey on them. AimsIn a 10-year study from 2008, we examine how small terrestrial vertebrates respond to the exclusion of introduced predators, the feral cat (Felis catus) and red fox (Vulpes Vulpes), introduced herbivores and the reintroduction of regionally extinct mammal species. MethodsDifferences in the yearly relative abundance of reptiles and mammals according to habitat type and whether sites were fenced or not, were tested using multivariate generalised linear models. Next, we calculated univariate P-values to identify individual species that showed significant relationships, positive and negative, with any of the explanatory variables. Key resultsTotal captures of reptiles were lower inside the conservation fence in all years, whereas total captures of small mammals were markedly higher inside the fenced area, notably in dasyurids. ConclusionOur results showed that conservation fences can deliver benefits for some fauna (but not all) beyond facilitating the reintroduction of highly threatened mammals. ImplicationsOur results demonstrated the consequential impacts of introduced predators on the Australian small mammal fauna, and showed that predator-exclusion fences can be an effective conservation intervention for this guild.

Space use and interactions of two introduced mesopredators, European red fox and feral cat, in an arid landscape

“…For range-resident feral cats, the observed extended home range (AKDE95) was about double the size of home ranges estimated for feral cats in another arid region of Western Australia (Wysong et al 2020), about three times that estimated for arid South Australia (Moseby et al 2009), and four times that estimated for subtropical savannas in northern Australia (McGregor et al 2015). This suggests that prey resources are more limiting in the semiarid woodland environments of our study area compared to regions with greater rainfall and/or more diverse reptile and small mammal faunas, for instance, rodents (see Roshier et al 2020). The near-constant movement by non-sedentary feral cats observed in this study has been observed in previous studies in semiarid or arid environments and has been attributed to nutritional stress (Jones and Coman 1982, Edwards et al 2001, Moseby et al 2009.…”

“…Approximately 8000 ha of the sanctuary is surrounded by an electrified conservation fence, within which foxes and cats have been excluded since 2007, and five threatened mammals have been reintroduced successfully (Roshier et al. 2020). A combination of poison baits and Canid Pest Ejectors is used to suppress foxes in a 36,000‐ha area to the south of the conservation fence at Scotia.…”

“…There is considerable overlap in the diet of feral cats and foxes in Australia (Catling 1988, Risbey et al 1999, Glen et al 2011, Molsher et al 2017, although feral cats are thought to prefer live prey (Dickman 1996b) and foxes have been shown to consume more carrion (Catling 1988). Reptiles are an important dietary component for cats in arid environments (Spencer et al 2014, Doherty 2015, and while there is a diverse reptile fauna at Scotia (Roshier et al 2020), they exhibit strong seasonality in the semiarid mallee region (Spence-Bailey et al 2010) with suppressed activity during the cooler months of the year Moseby 2001, Roshier et al 2020).…”

Consequences of the reintroduction of regionally extinct mammals for vegetation composition and structure at two established reintroduction sites in semi‐arid Australia

“…2009, 2018; Hutchison 2013; Fulton 2017; Roshier et al . 2020), levels of seed predation (Murphy et al . 2005; Mills et al .…”

Cat ecology, impacts and management in Australia

“…Cat-free islands and fenced areas have prevented the extinction of eight Australian mammal species, and further expansion should extend protection to other species that are highly susceptible to cat predation (Legge et al 2018). The ark network has focussed on threatened mammals and birds (especially on islands), but Roshier et al (2020) describe the effects of a large mainland fenced area on other species, showing that small mammals benefited from the exclusion of feral animals, but small reptiles did not, possibly because the reintroduced mammals competed with resources important to the reptiles, or preyed on the reptiles directly.…”