Abstract
Introduced mammalian predators can have devastating impacts on recipient ecosystems and disrupt native predator–prey relationships. Feral cats (Felis catus) have been implicated in the decline and extinction of many Australian native species and developing effective and affordable methods to control them is a national priority. While there has been considerable progress in the lethal control of feral cats, effective management at landscape scales has proved challenging. Justification of the allocation of resources to feral cat control programs requires demonstration of the conservation benefit baiting provides to native species susceptible to cat predation. Here, we examined the effectiveness of a landscape-scale Eradicat® baiting program to protect threatened northern quolls (Dasyurus hallucatus) from feral cat predation in a heterogeneous rocky landscape in the Pilbara region of Western Australia. We used camera traps and GPS collars fitted to feral cats to monitor changes in activity patterns of feral cats and northern quolls at a baited treatment site and unbaited reference site over four years. Feral cat populations appeared to be naturally sparse in our study area, and camera trap monitoring showed no significant effect of baiting on cat detections. However, mortality rates of collared feral cats ranged from 18–33% after baiting, indicating that the program was reducing cat numbers. Our study demonstrated that feral cat baiting had a positive effect on northern quoll populations, with evidence of range expansion at the treatment site. We suggest that the rugged rocky habitat preferred by northern quolls in the Pilbara buffered them to some extent from feral cat predation, and baiting was sufficient to demonstrate a positive effect in this relatively short-term project. A more strategic approach to feral cat management is likely to be required in the longer-term to maximise the efficacy of control programs and thereby improve the conservation outlook for susceptible threatened fauna.
Highlights
The introduction of mammalian predators outside their natural range can have severe consequences on recipient ecosystems [1,2,3] and be disruptive to native predator–prey relationships [4, 5]
The generalised linear mixed model (GLMM) analysis for feral cat detections showed no evidence of overdispersion in the full model (Pearson Chi2 = 745.4; df = 941.0), the R-square of the fitted model was 0.41 and the intercept-only model performed poorly in comparison (S2 Table)
While our study indicated that landscape-scale baiting using Eradicat1 does not remove all cats from the target area, there was evidence of a direct knockdown of cats, and evidence of a positive effect on northern quoll populations
Summary
The introduction of mammalian predators outside their natural range can have severe consequences on recipient ecosystems [1,2,3] and be disruptive to native predator–prey relationships [4, 5]. Once predators have established in an area, effectively controlling them poses a significant challenge [8, 9]. The detrimental impacts of introduced predators on native biodiversity can be seen in countries like Australia and New Zealand with disproportionately more extinctions of native species (mammals–Australia; birds–New Zealand) than other developed countries [2, 10, 11]. In Australia, predation by the introduced red fox (Vulpes vulpes) and feral cat (Felis catus) has been implicated in the decline and extinction of many native species [11,12,13]. Large scale fox-baiting programs have been shown to be relatively effective in reducing their impact on native fauna [14, 15]. There is some evidence that feral cat populations can increase in response to fox control [16, 17]
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