Rodents of the arid Northern Territory: conservation status and distribution

Abstract

At the time of European entry, 18 species of rodent occurred in the arid zone of the Northern Territory, including two endemic species, Zyzomys pedunculatus and Pseudomys johnsoni. The tally is somewhat inflated, as the arid Northern Territory is on the margins of the distribution for seven of these species. The historical record for this fauna is generally reasonably good, due to important collections around the end of the nineteenth century, some landmark studies (notably by H.H. Finlayson) earlier this century, documentation of Aboriginal knowledge, and the recent discovery and analysis of fossil and sub-fossil deposits. Notwithstanding this good historical baseline, recent research has added three native species to the fauna, and re-discovered one species, Z. pedunculatus, earlier feared extinct. Over the last 200 years, four species (Leporillus apicalis, Notomys amplus, N. longicaudatus and Pseudomys fieldi) have disappeared, and a further five species (N. cervinus, N. fuscus, P. australis, Rattus tunneyi and Z. pedunculatus) have declined considerably, with several of these perhaps no longer present in the area. The decline in this rodent fauna is matched, or indeed surpassed, by declines in the arid-zone bandicoots, small macropods and large dasyurids. But notably the small dasyurids have generally suffered few declines. There has been differential decline within the rodent fauna, with declines mainly affecting larger species, species with the most idiosyncratic diets, and species occurring mainly in tussock grasslands and gibber plains. The main conservation and management actions required to safeguard what is left of this fauna are carefully targetted studies examining the effect of threatening processes, complemented by landscape-wide amelioration of these threats. Additional autecological studies are also needed for some species, and some exceptionally poorly known areas should be surveyed. Current work examining the distribution, ecology and management requirements of the endangered Z. pedunculatus is a major priority.