Numerical and functional response of feral cats (Felis catus) to variations in abundance of primary prey on Stewart Island (Rakiura), New Zealand
Grant A. HarperZoology Department, University Of Otago, PO Box 56, Dunedin, New Zealand.
Wildlife Research 32(7) 597-604 https://doi.org/10.1071/WR04057
Submitted: 30 June 2004 Accepted: 24 August 2005 Published: 24 November 2005
Abstract
Few studies of populations of feral cats have simultaneously monitored the seasonal abundance of primary prey and the possible ‘prey-switch’ to alternative prey when primary prey abundance declines. On Stewart Island, when the abundance of feral cats’ primary prey, rats (Rattus spp.), was very low, significantly more cats died or left the study area than when rats were abundant. Cats preferentially preyed on rats regardless of rat abundance. Birds were the main alternative prey but cats did not prey-switch to birds when rat abundance was low, possibly owing to the difficulty of capture, and small mass, of birds compared with rats. On Stewart Island numbers of feral cats are restricted by seasonal depressions in abundance of their primary prey, coupled with limited alternative prey biomass.
Acknowledgments
The research was funded by Science and Research Division, Department of Conservation (Investigation No. 2501), the Miss E. L. Hellaby Indigenous Grassland Research Trust, and the Southland Conservancy, Department of Conservation. Thank you to my volunteers, Jo Joice, Pete Haverson, Simon Johnson, Kerry Borkin, Liz Meek, Glen Newton, Brent Sinclair, and the staff of Department of Conservation, Stewart Island, especially Phred Dobbins and Brent Beaven. Thanks also to staff of the Zoology Department, University of Otago. Kath Dickinson, Phil Seddon and Harald Steen provided supervisory support and, along with Mick Clout, Ian Jamieson, Denis Turner, Chris Jones and three anonymous referees, made comments on the text. Scott Davidson assisted with statistical analyses. This research was carried out under Otago University Animal Ethics Protocol No. 44/99.
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