Distribution and abundance of spectacled hare-wallabies and euros on Barrow Island, Western Australia

Abstract

Spectacled hare-wallabies (Lagorchestes conspicillatus) and euros (Macropus robustus isabellinus) occur on Barrow I. at densities of 42 and 8 km-2, respectively, which result in estimates of total population sizes of c. 10000 and 1800, respectively. Spectacled hare-wallabies occur throughout the island in all habitat types; euros tend to be concentrated in the deeply dissected country in the central-west of the island. Limited areas of floodout flats are important feeding areas for euros, being the only major habitat on the island dominated by grasses other than Triodia. There was no significant difference between density of either species on the two halves of the island (one half is dominated by a commercial oilfield; the other is relatively undisturbed). Barrow I. is the smallest island off the Australian coast to have successfully supported a population of large macropods for the 8000-10000 years since separation from the mainland by rising sea-level. Hence, the population estimate of euros on Barrow I. provides an empirical measure of the viable population size necessary for the long-term survival of large macropods. This estimate is nearly two orders of magnitude less than that estimated from a theoretical model of minimum viable population size (Belovsky 1987).