Population-Structure and Reproductive Status of Koalas on Raymond Island, Victoria

Abstract

In December 1980, 87 adult (>1-year-old) koalas (36 males, 51 females) were captured and marked on Raymond Island, in the Gippsland Lakes of Victoria. A further 85 adults and 34 juveniles (6-12 months old) were sighted but not captured. In August 1985, 25 females and 24 males were captured and examined. The proportions of animals in the older age classes (age classes 4 and above) were 61% in 1980 and 39% in 1985, while the reproduction rates were 38 and 40%, respectively. The low reproduction rates, and the high proportions of older animals in 1980, were attributed to reproductive tract disease, although the presence of this disease did not prevent the population from increasing to a density at which trees were being overbrowsed.