Aspects of the population ecology of the long-nosed potoroo, Potorous tridactylus (Kerr, 1792), in Southeastern Tasmania

The aim of this study was to describe the population parameters of a natural population of the long-nosed potoroo. The study was designed to be longitudinal in order to collect data over the entire lifespans of at least some individuals. Parameters of special interest were body mass and its relation to seasonality and home-range, survivorship, female reproductive activity in relation to maternal age, seasonality and breeding interval, and capture rates in relation to microhabitat. Capture / recapture data was systematically collected from a study area of approximately 35 ha at Porter Hill, five km southeast of Hobart. The study was designed to be longitudinal, potentially across generations of potoroos, and to also collect data for two syntopic species, the brown bandicoot and eastern bettong. A grid of ten transects, each of 20 sites, was trapped. Each trapping session was comprised of a transect trapped on two successive nights, with distant transects being trapped at successive sessions to minimise potential trapping impact on individual animals. Data from 134 such sessions form the basis of the thesis, some subsidiary data was also collected to supplement individual longevity data. Trappability of potoroos at Porter Hill was high compared with studies of potoroos on mainland Australia. Adult potoroos had a persistent male-biassed sex ratio over time. Sexual dimorphism was evident, with males having significantly greater body mass (based on both mean adult and maximum body mass) than females. Captures in traps occupied at a trapsite on a previous night were sex-biassed, with intra-sex avoidance of traps. Breeding in potoroos was aseasonal. Mean population density based on known-to-be-alive data for each sex was estimated to be 0.7 individuals ha -1 . A life table and survivorship curve are presented. Longevity patterns indicated uneven survivorship, with first-year mortality of around 80%, and some individuals living to eight years of age. Microhabitat selection was examined in relation to floristic diversity and vegetation structure. Sites were grouped on the basis of an agglomerative classification of floristic data, and analysis of variance was used to determine whether significant between-group differences in capture rates occurred. Vegetation groups were described, and appeared to vary with physical attributes of the local area. Significantly higher potoroo capture rates were obtained from one of the ten groups; a group comprised of floristically depauperate sites of open vegetation structure. Home range was examined using kernel analysis. A threshold number of captures which yielded a range asymptotic to the full home range area was determined by taking repeated random samples of differing sizes from individual capture-site data. Individuals with at least the threshold number of captures were examined further. Males had significantly larger home ranges than females, although considerable individual variation in home-range was also evident. Considerable overlap of both male and female home ranges occurred. The implications of these and related data for mating systems in the potoroo are discussed. The results are discussed in terms of the imputed mating system and trophic ecology of potoroos. Potoroos exploit a dispersed food resource, primarily hypogeal fungi. This, together with aseasonal breeding, is suggested to have led to a mating system where males have undergone sexual selection in body mass and home-range behaviour in order to search for and compete for access to receptive females. This social system is discussed in relation to that of other potoroids and comparable marsupials.