Biology of The Southern Brown Bandicoot (Isoodon Obesulus) In South-Eastern Tasmania. II. Demography.

Abstract

We used live-trapping to study the demography of two populations of the southern brown bandicoot, Isoodon obesulus, in south-eastern Tasmania from March 1992 to March 1995. The bulk of I. obesulus captures were in woodland/forest or within 3 m of its verge, with <10% of captures in 'open' pasture. Densities ranged from 0-0.35 animals/hectare. Both populations underwent a significant decline over the study period. This decline is thought to be the result of the exceptionally dry conditions over the three years of the study. Adult sex ratios (male/female) ranged from 0.6- 1.17. The sex ratio of pouch young was female-biased on both grids (range of 0.53-0.73). Isoodon obesulus were sexually dimorphic, with males being both heavier and larger than females. Only two juveniles were recruited to the populations over the entire three years of the study. Breeding among female I. obesulus was greatest in the December, low in the March, moderate in the September, and absent in the June trapping sessions. Mean litter size was 3.05 ± 0.26, with a range of 1-5 pouch young. For males and females, mean longevity for resident animals was 10.0 ± 3.7 and 13.5 ± 3.3 months, respectively. The mean home range area for the two resident males and the five resident females with ≥8 captures was 6.95 ± 1.95 and 3.28 ± 1.02 hectares, respectively. There was minimal overlap between the home ranges of individual I. obesulus.