Changes in mammal populations in relatively intact landscapes of Kakadu National Park, Northern Territory, Australia

Abstract

A previous study (Braithwaite & Muller 1997) reported substantial declines in mammal abundance over the period 1986-1993 for a large study area (300 km 2 ) within Kakadu National Park in the tropical savannas of northern Australia. This decline was reported as being a 'natural' response to fluctuating groundwater levels, driven by runs of poor wet seasons. We resampled mammals in this area in 1999, following a series of unusually good wet seasons, and examined the prediction that mammal numbers should have recovered. Increases in abundance were evident for four species: the smallest dasyurid (red-cheeked dunnart Sminthopsis virginiae) and the three smallest rodents (delicate mouse Pseudomys delicatulus, western chestnut mouse Pseudomys nanus and grassland melomys Melomys burtoni). In contrast, the abundance of all mammals combined and that for seven individual mammal species (northern quoll Dasyurus hallucatus, fawn antechinus Antechinus bellus, common brushtail possum Trichosurus vulpecula, northern brown bandicoot Isoodon macrourus, dusky rat Rattus colletti, black-footed tree-rat Mesembriomys gouldii and pale field rat Rattus tunneyi) continued to decline. The decline in abundance of these mammal species is consistent with limited observations elsewhere in northern Australia. Although far from conclusive, these observations suggest that the biota of the vast relatively undisturbed tropical savannas can no longer be assumed to be intact nor safe. Further research is needed to test this possible pattern of decline and, if confirmed, to identify and ameliorate the processes contributing to it.

Habitat connectivity, more than species’ biology, influences genetic differentiation in a habitat specialist, the short-eared rock-wallaby (Petrogale brachyotis)

“…Despite the Kimberley having relatively few threats in the past, human impacts associated with increased fire frequency and intensity, introduction of invasive species (e.g., cane toads), mining, grazing and predation by feral animals, threaten to cause faunal declines and extinctions (Braithwaite and Muller 1997;Eliot et al 1999;Fitzsimons et al 2010;McKenzie and Burbidge 2002;Woinarski 1992;Woinarski et al 2001). Our results indicate that West and East Kimberley populations of P. brachyotis are genetically distinct and could reflect a common pattern for other sandstone endemics (Potter et al 2012a).…”

Indigenous Knowledge of Rock Kangaroo Ecology in Western Arnhem Land, Australia

“…The nabarlek and short-eared rock-wallaby are small rock-wallaby species weighing less than 5 kg and the black wallaroo and common wallaroo are larger kangaroos (up to 22 kg and 47 kg respectively). Given recent reports of decline in populations of small mammal species in the region (Pardon et al, 2003;Woinarski et al, 2001) and the record of catastrophic extinction of small to medium-sized mammal species in other parts of Australia (Short and Smith, 1994), there is an urgent need for detailed information about the ecology of these species to ensure their conservation. Yet studying these species using scientific techniques is difficult because of their largely nocturnal and shy nature and the remote and inaccessible rocky areas they inhabit.…”

Landscapes without boundaries: wildlife and their environments in northern Australia

“…Recent broad-scale decline of the savanna fauna has been linked to our deliberate or inadvertent reduction in fine-scale heterogeneity, either through change from intricate to coarse-grained fire regimes or through the landscape-wide impacts of grazing by domestic and feral stock (Fisher 2001;Woinarski et al 2001;Yibarbuk et al 2001;Pardon et al 2003).…”