The short-term response of feral cats to rabbit population decline: Are alternative native prey more at risk?

Abstract

The impacts of invasive predators can be amplified by high densities of invasive prey species. In Australia, hyper abundant rabbit populations lead to high densities of feral cats and correspondingly high impact of cats on native species, especially small mammals. Therefore, it would be expected reducing rabbits could also reduce abundance of cats, and thereby alleviate predation on native small mammals. However, cats might respond to the loss of rabbits by prey-switching to native small mammals, resulting in increased predation on those species. Our aim was to understand the short-term effects of an experimental reduction of rabbit abundance on feral cats and their small-mammal prey in arid South Australia. We reduced the rabbit population in a 37 km2 experimental enclosure by ~ 80%, while monitoring an adjacent unmanipulated area as a control. Cat activity and survival of VHF-collared cats in the enclosure decreased by 40% following the rabbit reduction. Surviving cats increased their consumption of reptiles, birds and invertebrates, but they nevertheless evinced hunger by increased intake of experimentally-supplied sausages. There was no change in either the proportion of cat scats that contained remains of small mammals, or the rate at which video-collared cats were recorded killing small mammals, even though the activity of small mammals declined. Our results demonstrate that individual feral cats prey-switch in response to removal of their primary prey. However, we also show that survival and overall activity of cats decreased, which could result in net, long-term benefits for native prey threatened by cats. Management of feral cats using food lures or baits would also be more effective when introduced prey are scarce, as cats are more likely to eat novel food.

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Acknowledgements

Arid Recovery hosted and supported this project. They are an independent conservation and research initiative supported by BHP, The University of Adelaide, Bush Heritage Australia and The South Australian Department for Environment and Water. The rabbit removal effort was conducted by Frank Bernhardt (Bernhardt’’s Pest & Weed Control). Zac Richardson assisted with field data collection. Menna Jones, Greg Mutze, David Peacock, and Reece Pedler assisted with project development. Katherine Tuft and Catherine Lynch provided logistical support. Two anonymous reviewers provided expert advice for improving this manuscript. H McG and SL are supported by the National Environmental Program’s Threatened Species Recovery Hub.

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All authors conceived the ideas and designed methodology; HM collected and analyzed the data; HM led writing of the manuscript; and all authors contributed critically to the drafts and gave final approval.

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Correspondence to Hugh McGregor.

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The authors declare that they have no conflict of interest.

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Data collection fulfilled all legal requirements in Australia, and methods were approved by University of Tasmania Animal Ethics Committee (A0015720).

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McGregor, H., Moseby, K., Johnson, C.N. et al. The short-term response of feral cats to rabbit population decline: Are alternative native prey more at risk?. Biol Invasions 22, 799–811 (2020). https://doi.org/10.1007/s10530-019-02131-5

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Keywords

  • Prey switching
  • Animal-borne video
  • Diet
  • Mesopredator
  • Introduced predator
  • Invasive species
  • Wildlife