Julian W/Shutterstock. The numbat is one of the many Australian mammals in danger of extinction.

Australia's native mammals are under even more threat than previously realized, a new study has found. This is saying a lot, since ecologists were already aware that the continent's unique marsupials are dying out at an extraordinary rate.

Of the 273 land mammal species endemic to Australia since European settlement, 11% are already extinct and 21% are classified as threatened. By comparison, "only one native land mammal from continental North America became extinct" in 500 years, Professor John Woinarski of Charles Darwin University and his co-authors write in Proceedings of the National Academy of SciencesMore than a third of the world's mammals known to have died out since 1500 have been Australian natives.

Australia's animals suffer the same problem many island species do. Having lived for millions of years adapting to a unique evironment, they were unready for the arrival of voracious predators introduced by settlers. The paper pins the major blame on feral cat and European red fox populations, rather than the destruction of habitat, which has been the prime cause of species decline elsewhere in the world.

Australian marine mammals have survived much better, Woinarski notes. The small number of land species whose habitat extended beyond Australia have also suffered fewer losses.

Australian mammals form part of the local identity and are worth billions in tourism dollars every year. Nevertheless, the extinctions show no signs of slowing down. The last Christmas Island pipistrelle (Pipistrellus murrayi) died in 2009 and the Bramble Cay melomy (Melomys rubicola) is believed to have become extinct some time between 2006 and 2014. The authors add, “Most threatened and near threatened Australian land mammal species are continuing to decline.”

Ecological loss is even more severe than the numbers might suggest because some of those disappearing are highly distinctive, most famously the Tasmanian tiger (Thylacinus cynocephalus), which was the only member of its family still surviving at the time of colonization.

Feral species, once introduced, can be harder to stop than habitat loss, but the authors argue ignorance is a big part of the reason the destruction continues. “Other than the iconic thylacine, Australians, and the global community generally, have been relatively oblivious of this extinction calamity. In part, this is because many of the now lost species were obscure, small, nocturnal, and shy, and lived remote from most human settlement." 

With koalas now in decline and questions over the future of the platypus, this may change. However, even well-known species that were once widespread and numerous are now under threat. The authors give the example of the brush-tailed rock wallaby (Petrogale penicillata), which was so common that a single company sold almost 100,000 of its skins in the year 1908 alone. It is now classified as Near Threatened.

The one hopeful aspect the authors identify is the number of species that have survived on islands despite being eliminated from their mainland range, offering opportunities for reintroduction. More recently, “mainland islands” have been constructed by fencing off areas that are free from predators.

Credit: Eva Hejda via wikimedia commons. Perhaps the best known of the Australian species on the brink is the northern hairy-nosed wombat.

H/T BBC

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