Radio-tracked brush-tailed phascogales highlight the ecological importance of dead trees in Australian forests

Tree hollow-dependent wildlife species are increasingly at risk of decline because of continuing depletion of their hollow resources and the long lag-time for their renewal. We investigated patterns of hollow use in the brush-tailed phascogale (Phascogale tapoatafa), a regionally threatened mammal in the south of its range. Twenty-five phascogales (13 males and 12 females) were radio-tracked for a duration (mean ± s.e.) of 68.2 ± 15.8 days. This produced 318 diurnal nest-site detections, encompassing 88 individual hollows and 23 nest boxes. Dead trees were used on 70.4% of occasions despite comprising 27.7% of trees. The mean distance between consecutive diurnal shelters was 157.9 ± 65.9 m. Phascogales used up to eight nest sites (mean 3.2 per individual) but usually had one or two hollows which they used most frequently. Females used hollows with narrower entrances (mean: 6.3 ± 0.6 cm) compared to males (8.3 ± 0.6 cm). Internal measurements of accessible hollows showed that females selected hollows slightly larger, although not statistically different (24,846 ± 8131 cm3) from those of males (19,447 ± 5310.7 cm3). Our study has documented one of the highest frequencies of use of dead trees among studies on Australian marsupials and confirmed that this is a critical resource in forests where large trees are absent or uncommon. We observed a loss of 4.5% of these tree hollows over a 3-year period. Fire, storms and illegal firewood collection pose an ongoing threat to this vulnerable resource.