What makes Australian mammals so interesting?
Australia’s mammal fauna is exceptional. Australasia is the only place where representatives of the three surviving mammal lineages (monotremes, marsupials, eutherians) coexist and is the only continent dominated by marsupials. The effective conservation of this unique fauna now presents a major challenge.
In Australia, marsupials fill many of the mammalian niches (e.g., browser, grazer, folivore, insectivore, carnivore) occupied by eutherians in other continents. Absent from Australia’s native fauna are the familiar eutherian mammals (e.g., cattle, sheep, deer, horses, cats, dogs, weasels, rabbits, moles, monkeys) of the rest of the world, but present are marsupial equivalents of each, resulting in many stunning examples of convergent evolution. Australia also hosts a stunning array of native rodents and bats.
Due to its long-term isolation (~40 million years) as an island continent, the vast majority of Australia’s native marsupial (93%), rodent (91%) and microbat (73%) species are found nowhere else. In addition, our understanding of extant Australian mammal diversity remains incomplete, with new species being discovered regularly. Taxonomic uncertainty is highest amongst microbats, but also includes some groups of rodents and marsupials. Clearly the true diversity of Australian mammals is higher than currently understood.
Over recent millennia and especially in the last 200 years, this unique mammal fauna has suffered significant declines and extinctions, leaving the ecosystems of the continent profoundly changed. The European colonisation of Australia resulted in an avalanche of environmental change which continues to the present day. The widespread clearing and alteration of native vegetation and the introduction of exotic species (including 22 mammals), continues to have a profound impact on the native mammal fauna.
Within the last 200 years at least 25 species of Australian mammals (almost 10%) have become extinct and many more (20% of remaining species) are now threatened. This rate of mammal extinction is the highest in the world and represents a significant loss of unique biodiversity. These extinctions were not evenly spread across Australia but were concentrated on arid/semi-arid zone rodents, bandicoots and small macropods.
While much unique diversity has been lost, increased scientific knowledge and growing management expertise has prevented many further extinctions. However, in such altered environments, managing Australia’s unique mammals is a major challenge that includes encouraging the persistence of threatened species, as well as suppressing introduced mammalian competitors and predators and some native species that are now over-abundant.
While many threats to Australia’s mammals are ongoing and novel threats continue to arise, it is hoped that this unique fauna will persist and continue to fascinate in the centauries to come.
Dr Mark Eldridge
Principal Research Scientist, Australian Museum Research Institute
Eldridge M.D.B. and Herbert, C.A. (2015). Terrestrial mammal diversity, conservation and management in Australia. Pp. 298-319 in Austral Ark: The state of wildlife in Australia and New Zealand. A. Stow, N. Maclean, G.I. Holwell (eds). Cambridge University Press: Cambridge.