Sex-biased dispersal in the rufous bettong Aepyprymnus rufescens.

Abstract

STUDIES of dispersal and philopatry in Macropodoid marsupials have revealed strong sexdifferential patterns, consistent with those found in other mammals (Johnson 1989;Greenwood 1980). In the macropodids (kangaroos and wallabies), males disperse at sexual maturity, over distances several times greater than the diameter of their mother's home range. Females typically remain close to their birth place, often settling within the maternal home range, resulting in long-term association of female kin. Dispersal in potoroids (rat-kangaroos) is far less well understood. Although movements of adults have been studied in several species, there are only two indications of the pattern of natal dispersal and philopatry. Christensen and Maisey (1987) suggested that in the woylie Bettongia penicillata sub-adults probably dispersed over short distances, and that such dispersal was male-biased. Pope (2001) used microsatellite assignment tests and pairwise analysis of relatedness to infer that dispersal was also malebiased in B. tropica.Here we provide data on natal dispersal and philopatry from a large capture-mark-recapture study of the rufous bettong Aepyprymnus rufescens. We define natal philopatry as continued residence by an adult offspring in a home range overlapping that of its mother, and natal dispersal as a shift in the home range of the offspring large enough to result in no overlap with the mother.Aepyprymnus rufescens was studied at four sites in the Mt Fox area (145 o 46′ E; 18 o 50′ S), about 50 km west of Ingham in north Queensland. All sites were flat or gently undulating and covered by open eucalypt woodland dominated by Eucalyptus crebra, E. intermedia, E. tesselaris and E. peltata. Two of the sites had basalt-derived and two had granite-derived soils; population densities were estimated at 2.64 per km 2 and 11.45 per km 2 on the granite sites and 20.8 per km 2 and 36.7 per km 2 on the basalt sites. A 600 m x 600 m trapping grid was laid at each site, and trapped using 36 wire cage traps at 100 m spacings. Traps were baited with a mixture of rolled oats, peanut butter, vanilla essence and honey. Traps were set in the late afternoon, and were checked during the night. Bettongs (including furred pouch young) were marked with subcutaneous transponder ('PIT') tags, and pouch young were aged using the growth curve provided by Johnson (1978). All four sites were trapped at intervals of one or two months from early 1996 until the end of 1998. A typical trap session lasted three nights on each grid. This program resulted in a total of 1,344 captures of 163 individuals. The number of new animals caught on each grid plateaued after the first five or six nights of trapping, suggesting that all residents had been identified.A total of 39 individuals (21 males, 18 females) were marked as pouch young, and of these three males and seven females were subsequently recaptured as independent subadults or adults on their home grids. Of the three males marked as pouch young and later recaptured on their home grids, two were re-cap...

Dispersal and population structure of the rufous bettong,Aepyprymnus rufescens(Marsupialia: Potoroidae)

“…Genetic differentiation among local populations was produced mainly by short dispersal distances of adult females, as indicated by their higher F ST values. This was consistent with trapping data, which showed a tendency for young females to settle in home ranges adjacent to those of their mothers (Johnson & Payne 2002), while young males moved further from their mothers.…”

“…Results from trapping data also suggested a strong sex bias in dispersal. Only three of 21 male pouch young were recaptured as adults, and none were recaptured after more than 9 months, but seven of 18 females were recaptured all of which were breeding (Johnson & Payne 2002). This information is limited to the extent of the trapping grids (600 × 600 m), but suggests a bias in dispersal at this scale of 66–100% depending on mortality rates.…”

“…Fox; LR, n = 7), included for comparison. For additional trapping information refer to Johnson and Payne (2002). Ear biopsies were sampled from individuals in the population and stored in 70% ethanol.…”

“…Female rufous bettongs trapped at Mt. Fox were shown to be philopatric, with daughters tending to occupy ranges adjacent to their mothers and sons dispersing clear of the study grids (Johnson & Payne 2002).…”

Demography in relation to population density in two herbivorous marsupials: testing for source?sink dynamics versus independent regulation of population size

“…Studies elsewhere have recorded dispersal movements, both of males and females, of up to 10 km (Cowan et al 1996(Cowan et al , 1997Ward 1985). Most juvenile female and all juvenile male A. rufescens left their home grids, and those females that remained on their home grids moved outside the home-ranges of their mothers (Johnson and Payne 2002). Maximal dispersal distances of A. rufescens are not known, but they probably exceed those of T. vulpecula.…”