Management of invasive mesopredators in the Flinders Ranges, South Australia: effectiveness and implications

Abstract

ContextSignificant resources have been devoted to the control of introduced mesopredators in Australia. However, the control or removal of one pest species, such as, for example, the red fox (Vulpes vulpes), may inadvertently benefit other invasive species, namely feral cats (Felis catus) and rabbits (Oryctolagus cuniculus), potentially jeopardising native-species recovery. AimsTo (1) investigate the impact of a large-scale, long-term fox-baiting program on the abundance of foxes, feral cats and introduced and native prey species in the Flinders Ranges, South Australia, and (2) determine the effectiveness of a short time period of cat removal in immediately reducing feral cat abundance where foxes are absent. MethodsWe conducted an initial camera-trap survey in fox-baited and unbaited sites in the Flinders Ranges, to quantify the impact of fox baiting on the relative abundance of foxes, feral cats and their prey. We then conducted a secondary survey in sites where foxes were absent, following an intensive, but short, time period of cat removal, in which 40 cats were shot and killed. Key resultsNo foxes were detected within baited sites, but were frequently detected in unbaited sites. We found a corresponding and significant increase in several native prey species in fox-baited sites where foxes were absent. Feral cats and rabbits were also more frequently detected within baited sites, but fox baiting did not singularly predict the abundance of either species. Rather, feral cats were less abundant in open habitat where foxes were present (unbaited), and rabbits were more abundant within one predominantly open-habitat site, where foxes were absent (fox-baited). We found no effect of short-term cat removal in reducing the local abundance of feral cats. In both camera-trap surveys, feral cat detections were positively associated with rabbits. ConclusionsLong-term fox baiting was effective in fox removal and was associated with a greater abundance of native and introduced prey species in the Flinders Ranges. To continue to recover and conserve regional biodiversity, effective cat control is required. ImplicationsOur study showed fox removal has likely resulted in the local release of rabbits and an associated increase in cats. Because feral cat abundance seemingly fluctuated with rabbits, we suggest rabbit control may provide an alternative and more effective means to reduce local feral cat populations than short-term removal programs.

Long-Distance Movements of Feral Cats in Semi-Arid South Australia and Implications for Conservation Management

“…Numerous control programs in open landscapes have documented little subsequent change in the number of cats detected despite high levels of cat mortality [ 42 , 50 , 51 , 52 , 53 ]. One plausible explanation for these observations is that there is rapid reinvasion of individuals from surrounding areas, as reported from studies of similar meso-predators [ 54 , 55 , 56 ], including cats [ 11 , 42 ].…”

Cat ecology, impacts and management in Australia

“…The paper by Miritis et al (2020) shows how long-nosed potoroos (Potorous tridactylus) on French Island 'use' this principle, sticking to denser cover in areas with high cat activity. In a different example, Stobo-Wilson et al (2020b) suggest that controlling rabbits, themselves being a threat to many native plant species, in the Flinders Ranges of South Australia may be the most effective way to reduce cat impacts on native species, because cat density is inflated by the ready availability of rabbits.…”

“…Of course, interpreting a change in impact from feral predators as a direct result of the killing of pests is notoriously fraught, but Australian conservation programs are increasingly integrating monitoring into cat management to inform adaptive responses. Examples include a long-running program to control cats around remnant populations of western ground parrots (Pezoporus flaviventris; Comer et al 2020), a program to control foxes and cats in the Flinders Ranges (Stobo-Wilson et al 2020b), a program to monitor non-target responses to cat baiting at Matuwa-Lorna Glen (Wysong et al 2020), and a study to check for perverse outcomes from attracting cats to the perimeter of a successful fenced area at Arid Recovery in South Australia (McGregor et al 2020).…”

Experimentally testing the response of feral cats and their prey to poison baiting

“…Low intensity trapping and removal of cats in Tasmania, Australia actually caused an increase in cat activity and relative abundance at removal sites, possibly due to immigration by neighbouring cats into vacated territories (Lazenby et al 2014). In the Flinders Ranges, South Australia, the number of cat detections on cameras did not change after 40 cats were removed through trapping over two months (Stobo-Wilson et al 2020). On Rota Island, spotlight hunting of cats caused a modest knockdown within the first 18 months, but the population stabilised over the next 11 months (Leo et al 2018).…”