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Frontier population dynamics of an invasive squirrel species: Do introduced populations function differently than those in the native range?

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Abstract

Several squirrel species are biological invaders and their establishment in an area is often marked by ecological and economic costs to native species and forest crops. The eastern grey squirrel (Sciurus carolinensis Gmelin 1788) has been intentionally introduced multiple times outside of its native range but its success in establishing and spreading has not been consistent. An intensive live-trapping programme was designed to investigate the demography and population dynamics of populations of this species on the invasion frontier in the Republic of Ireland, a region marked by the slow but steady invasion of the grey squirrel. Low densities and high breeding rates distinguished these frontier populations. These results were placed in context with other frontier and established grey squirrel populations throughout their introduced and native ranges. As expected, variations in invasion speed and impact severity between regions were reflected in population demography. The highest densities, survival rates and breeding rates were recorded in Britain where the grey squirrel invasion has been most damaging. Careful comparative demographic study of invading populations could improve management outcomes, indicate differential invasibility of invaded communities, and offer clues to enhance the design of conservation reintroduction projects.

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Acknowledgments

Live trapping and tagging procedures were conducted under licences issued by the Irish National Parks and Wildlife Service (Licence Nos. C139/2011 and 05/2011). The authors thank the technical staff at UCC for assistance with equipment fabrication and E. Finnerty, A. Haigh, T. Kirakowski, V. Murphy, M. O’Grady, A. O’Shea, K. Sheehan, and E. Sheehy for assistance in the field. The authors are grateful to Coillte for site access and to two anonymous reviewers for helpful comments on a previous version of the manuscript. EAG was supported by the Irish Research Council.

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  1. School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland

    Emily A. Goldstein & Fidelma Butler

  2. Environmental Research Institute, Lee Road, Cork, Ireland

    Emily A. Goldstein

  3. Mammal Ecology Group, Zoology, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland

    Emily A. Goldstein & Colin Lawton

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Correspondence to Emily A. Goldstein.

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Goldstein, E.A., Butler, F. & Lawton, C. Frontier population dynamics of an invasive squirrel species: Do introduced populations function differently than those in the native range?. Biol Invasions 17, 1181–1197 (2015). https://doi.org/10.1007/s10530-014-0787-x

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