One size does not fit all: Intra– and interspecific variation of den site use in two marsupial glider species in fragmented forest

Habitat fragmentation poses challenges to arboreal mammals relying on tree hollows for denning. Knowledge of species-specific den preferences is needed to realise the full potential of restoration actions. Current advice regarding artificial den design is often highly rigid and specific, where there may be intra- and interspecific variation in den use that is not considered. We investigated denning preferences of the Sugar Glider (Petaurus breviceps) and Squirrel Glider (Petaurus norfolcensis) in remnant forest reserves, exploring the use of natural hollows and nest boxes, and which attributes of the dens were predictive of use. We radio-tracked 15 Squirrel Gliders and seven Sugar Gliders to denning locations where den characteristics were assessed and compared to randomly selected hollows not known to be used within the home range of the radio-tracked gliders. The hollow entrance size was the only variable that predicted den use in both species. Contrary to expectations, nest boxes were used proportionally more than natural hollows. This highlights that nest boxes can be an effective temporary solution to provide interim den sites for gliders in degraded forest remnants. Also contrary to expectations, hollow height showed only a weak correlation with den use. Seasonal variation and individual behaviours may influence glider preferences, emphasizing the need for nuanced management strategies. Based on these findings, we recommend against a one-size-fits-all approach in the application of artificial hollows for the restoration of glider denning habitat, especially in terms of the aspect and entry height, so that intra- and interspecific variation in den use can be accommodated.