Multiscale patterns of habitat use by the Carpentarian rock-rat (Zyzomys palatalis) and the common rock-rat (Z. argurus)

Abstract

This study examined the habitat requirements of the rare Carpentarian rock-rat (Z. palatalis) and those of the sympatric common rock-rat (Z. argurus). The environmental attributes of 15 study sites, 175 0.1-ha survey quadrats (within 21 sites) and 400 trap cells were summarised by classification and ordination analyses. Whereas Z. argurus was common and widespread throughout much of the environmental variation of sites, quadrats and trap cells, Z. palatalis was recorded from only 4 of 21 sites and 22 of the 175 quadrats. At the three scales examined, Z. palatalis responded strongly to a rockiness gradient, being restricted to the largest, most rugged gorge refuges, and locally was associated with scree piles and rocky slopes vegetated with dry monsoon rainforest and broadleaf woodlands. The richness of all plant species, rainforest plant species, plants bearing dietary items for Zyzomys spp., and shelter were shown to decline with decreasing rockiness and increasing disturbance by fire and cattle. The limited extent of suitable habitat at each of the four known Z. palatalis sites (c. <400 ha each), which is at continual threat from unmanaged fire, in particular, and grazing, will continue to place populations of Z. palatalis at risk of extinction.