Does tree hollow volume influence use by small arboreal mammals?

Identifying the specific tree hollow requirements of hollow dependent fauna is central to managing these shelter resources, as well as determining where habitat restoration is required. We installed pairs of carved tree hollows of different cavity volume at 14 sites to investigate whether preferences were shown by the brush-tailed phascogale (Phascogale tapoatafa), inland sugar glider (Petaurus notatus) and agile antechinus (Antechinus agilis). Small (1500 cm3) cavities should be of sufficient size to support non-breeding individuals, whereas large (9000 cm3) cavities should be required for breeding. Camera traps showed that the probability of visitation was highly seasonal but did not differ between hollow types for any species. Despite a high probability of visitation per week by all species (0.45–0.75, in summer), inspection of the hollows showed that few were occupied. Two phascogale nests were observed in large hollows and one in a small hollow. Nesting sugar gliders were seen in two large hollows and a nest was seen in another. No antechinus nests were recorded. Low occupancy of artificial hollows relative to high visitation, and compared with the results of other studies, is attributed to abundant natural hollows within our study area. Management of nest box programs requires careful planning that should include an evaluation of the existing tree hollow resource prior to any intervention.