Population demography of the eastern barred bandicoot (Perameles gunnii) at Hamilton, Victoria

Abstract

Totals of 32 female and 53 male Perameles gunnii were caught 241 and 330 times, respectively, during 4340 trap-nights at Hamilton, Victoria. Residents comprised 75.3% (n = 64) of the sample. Morphometric comparison indicates that P. gunnii is sexually dimorphic. Sex ratios (expressed in percentage of females) of 55% (dependent juvenile), 45% (independent juvenile) and 37.9% (adult) were determined. The age structure of the live-trapped population changed substantially between July 1989 (42.9% juvenile, 9.5% subadult and 47.6% adult) and August 1990 (46.2% juvenile, 15.4% subadult and 34.6% adult). The mean age of captured female bandicoots increased during the study, from 9.8 months in July 1989 to 15.8 months in August 1990. In all, 24 of 32 females produced 145 pouch young in 66 litters, with a mean W e . ) litter size of 2.2+/-0.1 (n = 66). The number of females that were lactating each month was high throughout the study (85%) and peaked during spring and autumn when all captured females were lactating. Sexual maturity for males and females occurred at about 5 and 3.5 months of age, respectively. The causes of mortality of P. gunnii between 1980 and 1990 included road death (63%, n = 85), cat predation (17.8%, n = 24), disease (8.1%, n = 11), trap death (5.2%, n = 7), machinery (3.7%, n = 5) and dog predation (2.2%, n = 3). A total of 25 P. gunnii died from unknown causes. Cat predation of P. gunnii may be high amongst juveniles and subadults but low for adults. A net emigration rate of 18% of individuals known to be alive indicates that the Hamilton Municipal Tip is a source for dispersal to other subpopulations. The 1990 distribution of the population was about 169 ha, within the City of Hamilton and adjacent Shire of Dundas, Victoria. There has been a decline in distribution and some local extinctions of P. gunnii in several areas between 1988 and 1990.