We used live-trapping to study the demography and movement of two populations
of the eastern barred bandicoot, Perameles gunnii, in
south-eastern Tasmania from 1992 to 1996. Densities were 0.35–2.35
animals ha–1. Sex ratios were male-dominated on
Grid I and female-dominated on Grid II. The average body weight for sexual
maturity was 700g for males and 680g for females, while the lowest recorded
weight for a breeding female was 570g. Perameles gunnii
was sexually dimorphic, with males having a greater body weight and pes length
than females. Recruitment was 25.4–32.1%, residence
46.7–100.0%, and emigration 16.5–25.5% of the
population. Three juveniles were recruited to the Grid I population, 55 to
Grid II, with a steady decline in the number of juveniles recruited to Grid II
over the four years of the study. Breeding occurred year-round. Mean litter
size was 2.53, with 78.2% of all litters having either 2 or 3 young.
Mean longevity for male and female P. gunnii was 7.91
and 10.54 months, respectively. Home ranges of males (4.29 ha) were
significantly larger than those of females (2.34 ha), although this may
represent a significant underestimate due to the small width of our grids
(200m) relative to the home-range area. There was only moderate overlap
(19.3%) between home ranges of males and females. The overlap between
male/male home ranges (4.4%) was significantly less than the
overlap between female/female home ranges (15.8%).
Perameles gunnii carried both ticks and fleas, with flea
infestation being significantly higher on Grid I than on Grid II.
Both populations underwent a significant decline over the study period,
apparently the result of the unusually dry conditions over the first 3 years
of the study. A deterioration in conditions was associated with a steady loss
of resident adults, declining recruitment of juveniles and an increase in the
male/female sex ratio. The sex ratio of P. gunnii
populations may provide a convenient index of habitat quality, with poor or
deteriorating conditions apparently associated with a high or increasing
numbers of males to females.
Sexual dimorphism in a top predator (
Notophthalmus viridescens
) drives aquatic prey community assembly
