Hollow use by vertebrates in the Top End of the Northern Territory

Information on forest use and dependence on tree hollows was collated for vertebrates in the Top End of the Northern Territory. The proportion of the total fauna that used hollows was 40% for mammals, 18% for birds, 20% for reptiles and 13% for frogs. Mammals had the highest proportion of species that: used forest; were forest dependent; used tree hollows; and the greatest proportion of forest species that used hollows frequently. Birds had the highest proportion of species that did not use forest but, because of their high numbers of species, they had the highest number of species using hollows. Only the reptiles had a consistently higher proportion of hollow-using species in the Top End when compared with national figures and two southern regional areas (Tasmania and southwest Western Australia) where forest was abundant. A greater proportion of threatened species are forest dependent compared with non-threatened species but the proportion of threatened and nonthreatened species that use hollows did not differ. Increased fire intensity in areas with exotic, high biomass pasture grasses and extraction of forest products, particularly didgeridoos, may be impacting on hollow availability at a local level.