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Assessing the impact of introduced cats on island biodiversity by combining dietary and movement analysis

Authors

  • S. Hervías,

    Corresponding author
    1. Animal Health Department, Faculty of Veterinary, Regional Campus of International Excellence ‘Campus Mare Nostrum’, University of Murcia, Murcia, Spain
    2. Island Ecology and Evolution Research Group (IPNA-CSIC), La Laguna, Spain
    3. Portuguese Society for the Study of Birds (SPEA), Lisboa, Portugal
    • Correspondence

      Sandra Parejo Hervías, Faculty of Veterinary, University of Murcia, Animal Health Department, Espinardo, Murcia 30100, Spain. Tel: +34 868 884 719; Fax: +34 868 884 147

      Email: shparejo@gmail.com

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  • S. Oppel,

    1. Royal Society for the Protection of Birds (RSPB), London, UK
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  • F. M. Medina,

    1. Island Ecology and Evolution Research Group (IPNA-CSIC), La Laguna, Spain
    2. Servicio de Medio Ambiente, Cabildo Insular de La Palma, La Palma, Spain
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  • T. Pipa,

    1. Portuguese Society for the Study of Birds (SPEA), Lisboa, Portugal
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  • A. Díez,

    1. Portuguese Society for the Study of Birds (SPEA), Lisboa, Portugal
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  • J. A. Ramos,

    1. Department of Life Sciences, Marine and Environmental Research Center (IMAR/CMA), University of Coimbra, Coimbra, Portugal
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  • R. Ruiz de Ybáñez,

    1. Animal Health Department, Faculty of Veterinary, Regional Campus of International Excellence ‘Campus Mare Nostrum’, University of Murcia, Murcia, Spain
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  • M. Nogales

    1. Island Ecology and Evolution Research Group (IPNA-CSIC), La Laguna, Spain
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  • Editor: Virginia Hayssen

Abstract

Populations of feral (not owned by humans) and domestic cats Felis catus coexist in most inhabited islands, and they have similar impacts on native species. Feral cats are generally believed to vary their diet according to prey availability; however, no previous studies of diet have tested this hypothesis on insular ecosystems with a limited range of available prey. Because domestic cats kill prey independently of hunger, the spatial extent of their impact on wildlife will be influenced by home-range size. In this study, we combined dietary information with cat movements to assess the impacts of feral and domestic cats on island biodiversity. We quantified the diet of cats from scat samples collected across one year and tested whether diet varies by season. The abundance of main prey categories was also estimated to document seasonal variation in prey availability for cats. Finally, we tracked domestic cats by global positioning system units in all four seasons to examine whether home-range patterns varied seasonally. The diet of cats constituted three prey groups (rodents, birds and invertebrates), and the seasonal variation in consumption of each taxon matched the seasonal variation in prey availability, thus supporting the generalist behaviour of cats on oceanic islands. Roaming behaviour varied among individuals and across seasons, but could not be explained by availability of prey. Unconfined cats had larger home-ranges than confined cats, but most domestic cats strayed <1 km from home. Thus, confinement of domestic cats might reduce the spatial extent of cat impact on native prey populations on oceanic islands.

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