Date of Award

1999

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Communications, Health and Science

First Supervisor

Adrianne Kinnear

Abstract

The small, enclosed section of Ellen Brook Reserve provided the unique opportunity to observe a population of southern-brown bandicoots (lsoodon obesulus) in the absence of exotic predators. The reserves small-enclosed size enabled it possible to trap the whole area (excluding the ephemeral swamps) and so emigration and immigration could be excluded. This enabled good population size estimates, and inferences on the loss of individuals due to mortality could be more strongly argued for. An understanding of the population structure, dynamics, size and density, and body condition of I. obesulus in Ellen Brook Reserve, will provide important information, for the development of future management programs and for the long-term survival of this species in closed reserves of this kind. Sampling was carried out on a monthly basis on four consecutive nights for five months and resulted in a high trap success of bandicoots (45%). The estimated population density of I. obesulus was high, ranging from 1.24 to 1.45 bandicoots ha-1 with a large degree of range overlap. The sex ratio of the adult population showed a large female bias 3:1, whereas the pouch young were close to parity. A larger proportion of the male population (50%) than the female population (20%) that were caught in the first three months were missing in August and September, suggesting a higher mortality rate of the males. A seasonal effect on body weights and intraspecific aggression (as evidence by increased scarring) was observed during this study. Sexual dimorphism was apparent with adult males being significantly heavier and larger than females. The population was dominated by sexually mature adults but with a continually increasing number of pouch young. Seventy four percent of the females were currying pouch young by September. Although the mean ± SE litter size was slightly smaller (2.1 ± 0.1) than found in other mainland I. obesulus populations the fecundity still appeared to be relatively high. Given the protection from exotic mammalian predators, this study suggests that I. obesulus numbers are able to build up in sufficient numbers from a small size, with a female-biased sex ratio. Although fecundity does not appear to be adversely affected by the small size of the reserve, males appear to show a higher mortality rate than females.

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