SOME DEMOGRAPHICS OF THE EXTIRPATION FROM THE WILD OF EASTERN BARRED BANDICOOTS (PERAMELES GUNNII) IN 1988-91 NEAR HAMILTON, VICTORIA, AUSTRALIA

The threatened, free-ranging mainland population of the eastern barred bandicoot in the Hamilton area of Victoria declined to near extinctio n in late 1992. Demographic changes associated with the decline were m onitored from 1988 to 1992. About 200 different animals were captured in 1988, 49 in 1989, 16 in 1990, 3 in 1991 and 3 in 1992; capture rate s (number of bandicoots captured per trap-night) displayed a similar p attern: 0.5 in 1988, 0.1 in 1989, 0.05 in 1990, 0.05 in 1991 and 0.02 in 1992. Observed declines lay within the 5% confidence intervals pred icted by a demographic model for a population subjected to a removal r ate of 14 animals per three months (the number removed for captive bre eding by managers). Removal of bandicoots to stock a captive populatio n hastened the demise of the wild population by about seven years; how ever, even in the absence of removals of animals, extinction was impen ding within 5-10 years. Sex ratios were male-biased in all years excep t 1988; the bias may have resulted from stochastic events. Average lit ter sizes did not differ between the 1988 population and subsequent po pulations, except for the 1991 population, in which a predominance of non-reproductive females contributed to a strong decline in average li tter size. These demographic trends illustrate how the synergy between stochastic and deterministic forces can rapidly drive a small populat ion to extinction.