Ecology of the western barred bandicoot (Perameles bougainville) (Marsupialia : Peramelidae) on Dorre and Bernier Islands, Western Australia

Population structure, reproduction, condition, movements and habitat prefer ence were assessed for western barred bandicoots (Perameles bougainville) o n Done and Bernier Islands over seven trapping sessions between 1988 and 19 95. Data comes from 372 captures of bandicoots in 2535 trap-nights (an aver age of 14.7 captures per 100 trap-nights). Trap success was 5.7-25.8% on Do ne and 5.7-7.6% on Bernier. Recaptures within a trip made up 29% of bandico ot captures. The overall sex ratio (excluding recaptures) was skewed heavil y towards males at 1.7:1 for trapped animals, but varied between male and f emale dominance at any time according to reproductive status of females. Se x ratio of pouch young was 1.2:1. Production of young was concentrated in t he wetter winter months. The smallest western barred bandicoot with pouch y oung weighed 175 g. Bandicoots showed a pattern of increasing litter size w ith size of mother. Females with young had an average litter size of 1.8, w ith young reaching independence at about 100 g body weight. Large testes si ze relative to body size in males suggested a promiscuous mating system. Bo dy condition could be predicted by sex (females were typically in better co ndition than males) and by rainfall over the previous 2 months. Some sexual dimorphism was evident, with females having longer heads and typically bei ng heavier than males. There was no detected dimorphism between island popu lations. Movements of bandicoots appeared limited, with the median distance moved by animals captured more than once within a 9-11-day trapping sessio n being 154 m. There was no significant difference in movements between the sexes, with males moving a median distance of 160 m and females 138 m with in trapping sessions. The greatest movement by a male was 1020 m while the greatest distance moved by a female was 490 m. Only 13% of recorded movemen ts were greater than 400 m. Home ranges overlapped, with 51% of traps catch ing more than one individual and as many as five males being caught at the same trap site. Bandicoots were widely dispersed through all habitats surve yed. Bandicoots appeared to suffer a substantial reduction in numbers on Do ne Island in a prolonged drought extending from October 1986 to April 1989, reducing overall trap success to less than 6% in the 1988 survey.