Factors influencing population dynamics in island and mainland populations of the swamp antechinus (Antechinus minimus)
Michael G. Sale A C , Barbara A. Wilson B and John P. Y. Arnould AA School of Life and Environmental Sciences, Deakin University, Burwood, Vic. 3125, Australia.
B Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, WA 6983, Australia.
C Corresponding author. Email: miale@deakin.edu.au
Australian Journal of Zoology 56(3) 187-194 https://doi.org/10.1071/ZO08076
Submitted: 13 May 2008 Accepted: 27 August 2008 Published: 27 November 2008
Abstract
Simultaneously analysing demographic processes of small mammals living in different ecological contexts may help to understand mechanisms that influence the growth and decline of these populations. The size and demography of swamp antechinus (Antechinus minimus) populations located in a coastal mainland habitat and on a small offshore island in south-eastern Australia were investigated. Large demographic differences occurred between the two ecosystems, with the island population density often 100 times greater than that on the mainland. The swamp antechinus in the mainland habitat was influenced by extrinsic climatic forces, with juvenile recruitment, individual body mass and overall population size being affected by rainfall, a factor likely to influence food availability for the species. However, the island population did not appear to be affected by drought to the same degree where allochthonous marine nutrient inputs may have offset any drought-induced reduction in primary production. Significantly greater juvenile recruitment in the island habitats combined with restricted emigration and potentially reduced predation and interspecific competition are likely to be responsible for the high population densities on the island. Although island populations appear robust, future conservation efforts should focus on mainland populations given the genetic deficiencies in the island populations.
Acknowledgements
We gratefully acknowledge the logistical support provided to this project by Parks Victoria, Tidal River, particularly by M. Hoskins and field assistance by M. Underwood, J. Sale, J. Egan, and K. Hicks. This research was generously funded by a Holsworth Wildlife Research Endowment, the Winifred Violet Scott Estate, the Australian Geographic Society, M. A. Ingram Trust, a Wildlife Preservation Society of Australia university student grant, an Ethel Mary Read research grant from the Royal Zoological Society of New South Wales, a student award from the Ecological Society of Australia and a Deakin University Ph.D. scholarship to MGS. All work was carried out under an approved Department of Sustainability and Environment Wildlife research permit (#10003288) and approval by the Deakin University Animal Welfare Committee (#A16/2005).
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