Tropical Savannas CRCNatural Heritage Trust

Mammal decline in Australia: Box with Euan Ritchie Antilopine wallaroo project

Mammal decline in Australia

In the last two centuries half of the world’s mammal extinctions have occurred in Australia (Short & Smith, 1994), bestowing on this country the worst record of mammal conservation globally. Much of the research into Australia’s declining marsupial fauna focused on the effect of European settlement on species that fall within the ‘critical weight range’, animals which have a mean adult body weight between 35 and 5500 grams (Burbidge & McKenzie, 1989; Calaby & Grigg, 1989; Johnson et al., 1989, Morton, 1990; Short & Smith, 1994 & Smith & Quin, 1996).

It was widely accepted that species falling within this weight range were more prone to extinction than species that lay outside the weight range. This argument was recently refuted by Cardillo and Bromham (2001), who argued that the perceived resistance of contemporary large marsupials to extinction may be an artefact of the end of Pleistocene extinction event, which removed the large extinction-prone mammals.

Despite this, some large marsupials, particularly kangaroos, have managed comparatively well and even proliferated in the presence of deleterious factors affecting small marsupials—though a prominent exception is the northern hairy-nosed wombat (Lasiorhinus krefftii), which is currently threatened with extinction (Hoyle et al. 1998).

Rapid decline under way in the north

At present a large-scale mammal decline appears to be occurring throughout the monsoonal tropics of Australia, particularly within savanna environments (Woinarski et al., 2001). Woinarski and Ash (2002) provide evidence that this decline may in part be associated with habitat changes resulting from pastoralism and altered fire regimes.

Until recently it was presumed that the fauna of the monsoonal tropics remained largely intact. Woinarski et al. (2001) warn that past extinction events in central Australia were extremely rapid, with changes in abundance leading to the loss of species occurring within one to two decades. Further work by Franklin (1999) details widespread declines of granivorous birds that overlap those areas with reported mammal declines. Broad changes in the understorey species composition and phenology arising from altered fire regimes and pastoralism, are again associated with declining species.

Explore this article in Land Manager.