Ecology of burrowing bettongs, Bettongia lesueur (Marsupialia : Potoroidae), on Dorre and Bernier Islands, western Australia

Population structure, reproduction, condition, morphology, movements, habit at preference, and dynamics of the burrowing bettong were assessed on Dorre and Bernier Islands between 1988 and 1995. The data come from 982 captures of bettongs in 2661 trap-nights (an average of 37 captures per 100 trap-ni ghts). Recaptures within a trip made up 39% of bettong captures. Bettongs w ere more abundant, as indexed by trap success, than were western barred ban dicoots (the other species caught in considerable numbers on trapping grids ). Sex ratio of bettongs (excluding recaptures) were skewed heavily towards males at 1.43 : 1 despite approximate parity in pouch young. Production of young was concentrated in the wetter winter months and appeared to fall we ll below their theoretical capacity of 3 young per year. Bettong females we re capable of producing young at 880-900 g (approximately 7-8 months of age ) but incidence of females with pouch young or showing signs of recent lact ation increased from 40% for females of 881-1000 g to 62% for females > 100 0 g. The incidence of sub-adult bettongs in the population peaked in spring , but varied between years (range 0-14% of the population). There was an ex cess of males over females in the sub-adult population. Bettongs showed lit tle sexual dimorphism but there were significant differences in morphology between the two island populations. Bettongs appeared to suffer substantial reductions in numbers in a prolonged drought extending from October 1986 t o April 1989, reducing trap success for this species to 19% in the 1989 sur vey. Numbers grew strongly on both islands after the breaking of the drough t in May 1989, showing an observed rate of increase of r = 0.75 on Dorre Is land. Trap success had increased to 45% in September 1991. There was a high turnover of bettongs on trapping grids - 25-40% over 6 months to 80% over 3 years. Movements of bettongs appeared limited: the median distance moved by bettongs captured more than once within an 8-day trapping session was 16 0 m. Only 4% of recorded movements were greater than 1 km. There was no sig nificant difference in movements between the sexes. Bettongs were widely di spersed in winter through the four habitats surveyed but tended to concentr ate in dune and Triodia sandplain habitat in autumn and spring.