Context. Small mammals are undergoing significant declines across the tropical savannas of northern Australia despite a lack of widespread land clearing. The causes of these declines remain unresolved, but a growing body of evidence suggests that the structural simplification of savannas, namely the degradation of under- and overstorey vegetation by frequent fires and high densities of exotic megaherbivores, is likely to be a significant contributing factor.
Aim. We sought to investigate how declining mammals use critical denning resources in high-biomass mesic savannas to help explain drivers of mammal decline in more open and less mesic areas and inform management priorities.
Methods. We fitted VHF/GPS collars to nine northern quolls (Dasyurus hallucatus), an Endangered scansorial predatory mammal, from a remnant population located on bauxite plateaus on Cape York Peninsula, Australia, to monitor their nocturnal movement patterns and den use over 1 month.
Key results. During this period, northern quolls exclusively denned in trees (either standing hollow trees or fallen logs). The most frequently used den trees tended to be larger, with pronounced trunk leans and multiple hollow entrances from 5 to 20 cm in diameter, whereas the most frequently used den logs tended to be longer and had more hollow entrances from 10 to 20 cm in diameter. All home ranges were confined to the high-biomass savanna habitat found on the bauxite plateaus, with males having a mean home range almost double the size of the mean female home range.
Conclusions. The reliance of this population of northern quolls on large hollow-bearing trees for shelter may explain the regional contraction of the northern quoll to high-biomass mesic savannas with an abundance of large trees.
Implications. These high-biomass savanna habitats, such as the bauxite plateaus found on the Cape York Peninsula, are likely to be critical for the persistence of the northern quoll, and should be appropriately protected, through management of fire and avoidance of clearing and logging.
