Collectively, the world's last 20 Christmas Island pipistrelle bats (Pipistrellus murrayi) weigh less than a fifth of a pound (around 60 grams). That's not much mass for any species – let alone one on the razor's edge of extinction.

It's been a rough few years for this tiny Australian micobat. Once fairly common on its home island, populations have dropped dramatically in the last decade, first to 100 bats in 1994, then to 54 three years ago. Today, according to Lindy Lumsden, a research scientist at Australia's Department of Sustainability and Environment, there may be just 20 left. Lumsden now warns the Christmas Island pipistrelle may be extinct in as little as six months if the current rate of decline continues.

So what's causing the bats' disappearance? No one knows for sure. Most of Christmas Island is a national park, so the bats' habitat is protected. The area features an abundance of insects, so they should have plenty of food.

But Christmas Island has also become home to several invasive, introduced species, including black rats, feral cats, and tree-climbing Asian wolf snakes, which could all be predating upon the bats. The yellow crazy ant (Anoplolepis gracilipes) has also caused great damage to many Christmas island species, including its famous red crabs, and could be killing the bats as well.

Disease could also be a possibility, although Lumsden's research, published on the website of the Australian Bat Society, hosted by Charles Stuart University, Thurgoona, Australia, has not turned up any evidence of such.

In order to save the pipistrelle from extinction, Lumsden has proposed gathering all of the bats from the wild and creating a captive colony, where they can breed in safety. "If sufficient animals can be caught and they acclimatise to captivity," she writes, "a commitment will then need to be made to a long-term (10-year) breeding program to enable sufficient animals to be bred for a release program."

Lumsden has pled for support from the Australian government, a call Minister for Environment Peter Garrett today declined, saying there are "unacceptably high risks involved in embarking on an immediate captive breeding program," and "the bats are also very hard to catch and no one knows how to keep them alive for breeding." (Evidently, to paraphrase Midnight Oil—the band Garrett used to front—you can sleep while the bats are dying.)

So is this the end of the line for the Christmas Island pipistrelle? For now, it's a waiting game.

Bonus: See our in-depth report for more on bats.

Image: Common pipistrelle (Pipistrellus pipistrellus), a relative of the Christmas Island pipistrelle, via Wikipedia