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Density dependence in foraging habitat preference of eastern grey kangaroos

Authors

  • Daniel Ramp,

  • Graeme Coulson


D. Ramp and G. Coulson, Dept of Zoology, Univ. of Melbourne, Victoria 3010, Australia (present address DR, Inst. of Wildlife Research, School of Biological Sciences, Univ. of Sydney, New South Wales 2006, Australia [dramp@bio.usyd.edu.au]).

Abstract

For a free-ranging forager, the suitability of a patch is dependent on population density, resource supply, resource quality, and the costs of foraging or dispersal. We quantified differences among three foraging habitats and compared this variation to temporal patterns of habitat preference by free-ranging eastern grey kangaroos, Macropus giganteus. We investigated selection on a fine-grained spatial scale, and asked whether habitat preference is constrained by density-dependent mechanisms. Variation in the quantity and quality of resources among habitats was greatest during spring, when biomass and quality were highest, and differences among habitats were most pronounced. However, consistent and discernable differences among habitats were not obtained, indicating that the system fluctuated around an equilibrium state. Using isodar regressions to examine the consumer-density relationships among habitats, open-woodland habitat was favoured over the two open-forest habitats for foraging. Seasonal isodars indicated that density dependence regulated preference between the three foraging habitats during autumn, spring and summer, but not during winter, when variability in resources among habitats was lowest.

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