Reversed sexual dimorphism and altered prey base: the effect on sooty owl (Tyto tenebricosa tenebricosa) diet

The ecology and function of many Australian predators has likely been disrupted following major changes in prey base due to declines in distribution and abundance of small mammals following European settlement. This study investigated various aspects of the dietary ecology of sooty owls (Tyto tenebricosa tenebricosa), including sexual variation as they potentially exhibit the greatest degree of reversed sexual dimorphism of any owl species worldwide. Sooty owls are highly opportunistic predators of non-volant small mammals, consuming most species known to exist in the region, so their diet fluctuates seasonally and spatially due to varying prey availability, and is particularly influenced by the breeding cycles of prey. Significant intersexual dietary differences existed with female sooty owls predominantly consuming much larger prey items than males, with dietary overlap at 0.62. The current reliance on relatively few native mammalian species is of conservation concern, especially when mammal declines are unlikely to have ceased as many threatening processes still persist in the landscape. Sooty owl conservation appears inextricably linked with small mammal conservation. Conservation efforts should be focussed towards improving prey densities and prey habitat, primarily by implementing control programs for feral predators and preventing the loss of hollow-bearing trees throughout the landscape.

The long-term effects of logging for woodchips on small mammal populations

Context. Long-term studies are internationally recognised as an essential component of achieving ecologically sustainable forest management with respect to fauna. Aims. This study aimed to assess longer-term responses of small mammals to logging by returning in 1998 to our 1980–83 study sites in south-eastern New South Wales, Australia. Methods. Three age-classes of forest were surveyed: unlogged; 18–19-year-old regrowth; and 26–34-year-old regrowth. Key results. Rattus fuscipes remained affected by logging, and there were significantly fewer R. fuscipes males in logged, north-west-facing sites than at other sites, although the effect was less pronounced in 1998 than in 1980–83. Antechinus agilis females were significantly less numerous in south-east-facing, unlogged forest. This was not expected from the 1980–83 results. Antechinus swainsonii, which had disappeared following a fire in 1980, had returned to the forest by 1998. A. swainsonii females showed a significant preference for south-east-facing slopes and this relationship was consistent between logged and unlogged forest. No members of Mus musculus or Sminthopsis leucopus, which were present in 1980–83, were caught in 1998. Conclusions. As in the 1980s study, the responses of small mammal species to logging history were varied and species specific. Implications. In our study area, we predict that sustained logging for woodchips will continue to deplete its populations of small mammals. This adds to the case for a more robust and sustained approach to researching and managing our forest fauna.

Patterns of movement in the small dasyurid (Ningaui yvonneae)

The movement behaviour of a small dasyurid (Ningaui yvonneae) was investigated using mark–recapture data collected over 28 months from a population in the Middleback Ranges, South Australia. We were particularly interested in assessing variability in patterns of movement between the sexes and across seasons, as this has potentially important implications for population composition and dynamics. The species was found to be fairly mobile, with frequent and sometimes large movements relative to the size of the animal (up to 900+ m). Average distances moved between recaptures within and between trap sessions were 84 m and 160 m respectively, with nearly half of all recorded movements being between trapping grids (i.e. >80 m). Relatively high recapture rates (many separated by more than 100 days) and measures of site fidelity indicated that the species was not particularly transitory, but probably establishes large and/or drifting home ranges. However, patterns of movement varied considerably according to sex and the time of year. Female N. yvonneae were generally more sedentary than males, with few females moving between trapping grids, and most short-term movements (<100 days apart) being less than 70 m. Movements of females for which the records were separated by more than 100 days tended to be larger, with an average between-capture distance >200 m. In contrast, males often moved between trapping grids, even over short periods. Some short-term movements were more than 600 m in length, and the average distance moved within trapping sessions was >100 m. During the breeding season, males more than doubled the average distances moved between recaptures, when they were presumably roaming in search of females. For females, movement distances were similar during the prebreeding and breeding seasons, but were significantly smaller in the postbreeding season, when they were caring for young.

Differential habitat use by a local population of subadult common dunnarts, Sminthopsis murina, following wildfire in coastal wet heath, New South Wales, Australia

Little has been published about Sminthopsis murina, a small insectivorous marsupial encountered infrequently during trapping studies. Individuals favour vegetation associations found in recently burnt heathlands and forests; however, individuals rarely remain in such areas long enough for repeated capture. We report an unusual occurrence of habitat fidelity by a dense population of subadult S. murina in coastal wet heath, New South Wales, Australia. Individuals were captured repeatedly in the first 16 months following wildfire (30 subadults trapped 154 times: recapture rate = 80%). Densities peaked 10 months after fire at 3.75 individuals ha–1. More males than females were captured (23 males, 7 females). Habitat analyses revealed differential use of regenerating coastal wet heathland by S. murina. Significantly more captures were made in areas of high soil moisture in the first six months following fire. Captures then decreased in these areas but increased where soil moisture had been lower and where vegetation had been growing more slowly. Beyond the 1995/96 breeding season, regenerating vegetation became increasingly dense and less patchy and captures of S. murina ultimately declined to zero. This paper records a rare opportunity to examine habitat preferences of a single cohort of subadult S. murina. Habitat use may have been determined by the presence of a narrow range of vegetation structure.