The conservation status of rodents in the monsoonal tropics of the Northern Territory

Abstract

The rodent fauna of the monsoonal tropics of the Northern Territory comprises 23 native species and two introduced species. Three species (Zyzomys maini, Z. palatalis and Pseudomys calabyi) are endemic to the area, and four species (Pseudomys hermannsburgensis, P. desertor, P. johnsoni and Notomys alexis) enter the area only on its southern (arid) fringe. The rodent fauna is closely related to that of the Kimberley, Western Australia.

Distribution maps for all species are given. One species (Z. palatalis) has an extremely restricted range and is regarded as critically endangered. The lack of information on the distribution and abundance of rodents in general in this area is evident in the national classification of five of its species (Xeromys myoides, Mesembriomys macrurus, Notomys aquilo, Pseudomys desertor and Pseudomys johnsoni) as Insufficiently Known. The two introduced rodents (Mus domesticus and Rattus rattus) are virtually restricted to urban and highly modified areas, although R. rattus also occurs on one uninhabited island.

In contrast to that of much of the rest of Australia, this rodent fauna has apparently retained its full complement of species since European colonisation. This enduring legacy is attributable largely to the relatively limited modification of its environments. However, three species (Mesembriomys macrurus, Rattus tunneyi and Conilurus penicillatus) appear to be declining. The pattern of decline in these species, and in the mammal fauna generally, is obscured by the very limited historical data. However, declines appear most pronounced in the cattle country of the Victoria River District and Gulf regions.

Priorities for the management of this rodent fauna include survey of poorly known areas, survey for poorly known species, monitoring of rodent communities, and landscape-wide management of the three pervasive processes with probably greatest impacts – fire, grazing and feral predators.