Degrees of population-level susceptibility of Australian terrestrial non-volant mammal species to predation by the introduced red fox (Vulpes vulpes) and feral cat (Felis catus)

Abstract

Context Over the last 230 years, the Australian terrestrial mammal fauna has suffered a very high rate of decline and extinction relative to other continents. Predation by the introduced red fox (Vulpes vulpes) and feral cat (Felis catus) is implicated in many of these extinctions, and in the ongoing decline of many extant species. Aims To assess the degree to which Australian terrestrial non-volant mammal species are susceptible at the population level to predation by the red fox and feral cat, and to allocate each species to a category of predator susceptibility. Methods We collated the available evidence and complemented this with expert opinion to categorise each Australian terrestrial non-volant mammal species (extinct and extant) into one of four classes of population-level susceptibility to introduced predators (i.e. ‘extreme’, ‘high’, ‘low’ or ‘not susceptible’). We then compared predator susceptibility with conservation status, body size and extent of arboreality; and assessed changes in the occurrence of species in different predator-susceptibility categories between 1788 and 2017. Key results Of 246 Australian terrestrial non-volant mammal species (including extinct species), we conclude that 37 species are (or were) extremely predator-susceptible; 52 species are highly predator-susceptible; 112 species are of low susceptibility; and 42 species are not susceptible to predators. Confidence in assigning species to predator-susceptibility categories was strongest for extant threatened mammal species and for extremely predator-susceptible species. Extinct and threatened mammal species are more likely to be predator-susceptible than Least Concern species; arboreal species are less predator-susceptible than ground-dwelling species; and medium-sized species (35 g–3.5kg) are more predator-susceptible than smaller or larger species. Conclusions The effective control of foxes and cats over large areas is likely to assist the population-level recovery of ~63 species – the number of extant species with extreme or high predator susceptibility – which represents ~29% of the extant Australian terrestrial non-volant mammal fauna. Implications Categorisation of predator susceptibility is an important tool for conservation management, because the persistence of species with extreme susceptibility will require intensive management (e.g. predator-proof exclosures or predator-free islands), whereas species of lower predator susceptibility can be managed through effective landscape-level suppression of introduced predators.

Habitat and introduced predators influence the occupancy of small threatened macropods in subtropical Australia

“…Although it is widely accepted that birds, reptiles and small mammals are the preferred prey of feral cats in densely forested habitats, feral cats also prey upon mediumsized mammals (Doherty et al, 2015;Radford et al, 2018). Although it is widely accepted that birds, reptiles and small mammals are the preferred prey of feral cats in densely forested habitats, feral cats also prey upon mediumsized mammals (Doherty et al, 2015;Radford et al, 2018).…”

Systematic planning can rapidly close the protection gap in Australian mammal havens

“…We define comprehensive to be the inclusion within the haven network of populations of all 67 mammal taxa that have “high” or “extreme” predator susceptibility, as defined by Radford et al. (). We acknowledge that this focus does not consider other Australian taxa (particularly birds and reptiles) that are susceptible to introduced predators (Woinarski et al., , ), and may benefit from fences.…”

“…Sixty‐seven extant Australian mammal taxa are extremely or highly susceptible to introduced predators (Legge et al., ; Radford et al., ). For each taxon, we produced historic distribution maps, based on occurrence records from the Mammal Action Plan (Woinarski et al., ) superimposed onto Interim Biogeographic Regionalization for Australia (IBRA, Commonwealth of Australia, ) subregions (these divide the Australian mainland into 419 biogeographical units).…”

“…In previous publications, we have: (1) summarized the susceptibility of Australian terrestrial nonvolant mammal species to introduced predators, thus identifying the species that need representation within havens (Radford et al., ); (2) analyzed the extent to which the current haven network protects predator‐susceptible threatened mammals (Legge et al., ); (3) identified areas of inefficiency in the current haven network at a national scale (Ringma et al., ); and (4) developed methods for the systematic allocation of new havens (Ringma et al., ). Here, we integrate the findings of these studies into principles for a strategic national network of havens, as a guide for its future expansion.…”

Australian birds could benefit from predator exclusion fencing

“…Introduced cats ( Felis catus ) and foxes ( Vulpes vulpes ) are leading causes of extinction and decline in Australian wildlife (Kearney et al, ). Their greatest impact has been felt by mammals (Radford, Woinarski, Legge, Baseler, & Bentley, ), however, they have also had a massive impact on birds (Woinarski et al, ). Seventy‐one out of Australia's 117 listed bird species (61%) are recognized to be predated by either cats (Woinarski et al, ).…”