Ecology and conservation of the antilopine wallaroo: an overview of current knowledge

The antilopine wallaroo (Macropus antilopinus) is restricted entirely to the tropical savannas of northern Australia and, along with the black wallaroo (Macropus bernardus), remains the least studied of the large macropodids. There is currently great concern that many of the endemic mammals of this region are undergoing declines in their distribution and population size; without detailed ecological information, proactive management to prevent further declines will be difficult. Between 2002 and 2005, I conducted an extensive study of the ecology and conservation of the antilopine wallaroo at 50 sites across the species' entire distribution. I calculated relative density estimates for each site using line transects and recorded the vegetation characteristics, fire history and resource availability at each site. I collected detailed information on the socioecology and behaviour of antilopine wallaroos and other sympatric macropodid species opportunistically. This information, together with that of previously published studies, is presented in the form of a general overview of the ecology and conservation of the antilopine wallaroo. The antilopine wallaroo has a wide but patchy distribution across northern Australia, with a mean abundance of three animals per square kilometre (range 0.33-31). I identified the availability of permanent water, frequency of fire and the density of eastern grey kangaroos (Macropus giganteus) as the factors that most strongly influenced antilopine wallaroo abundance. In the tropics, the antilopine wallaroo is the most gregarious of the macropodid species, with an average group size of three. Group composition changes from predominantly mixed in the wet season, the time of mating, to largely all-male and all-female groups in the dry season (non-breeding period). At one site in Queensland, antilopine wallaroos fed predominantly on grass, particularly black speargrass (Heteropogon contortus), but forbs constituted 5-6% of the diet, which varied seasonally and between sexes. Under climate change scenarios predicted for northern Australia, the antilopine wallaroo may experience a severe range contraction, with possible extinction by 2070.