Australia is a world leader in species extinction and declines, largely due to invasive species.
Extinct: Christmas Island pipistrelle
These tiny bats were so plentiful on Christmas Island during the early 1900s they ‘used to fly in through the open doors, and now and then you could see one fall off the light, or off somewhere onto the table, or into someone’s soup’.
Until the mid-1980s they remained common, then surveys in 1994 and 1998 recorded sharp declines. By 2005, there were 80% fewer than in 1994.
Biologists were commissioned to investigate the bat’s decline. After ruling out disease, they concluded in their 2007 report that the only other possible threats were various introduced species, all of which appeared to be increasing – Asian wolf snakes, giant centipedes, giant African snails, feral cats, black rats and nankeen kestrels. They could not decide which among these had caused the decline, but noted that wolf snakes, arriving in the 1980s, were the only ones to reach the island just before the bat tanked and whose advance mirrored the bat’s decline.
Doubts about the snakes – did they climb high enough up trees to reach bats roosting under bark or in hollows? did they use dense rainforest or keep to road edges and other disturbed locations? – were answered when an infra-red camera trained on the trunk of a pipistrelle roost tree photographed a climbing wolf snake inside rainforest far from any road.
In 2006, when the government’s Threatened Species Scientific Committee assessed the bat as critically endangered, they suggested captive breeding was needed.
The original team of biologists also recommended captive breeding the following year. In January 2009, by which time as few as 20 bats remained, the Australasian Bat Society urged immediate action on captive breeding. On 1 July the minister agreed the last bats could be captured, but by the time bat biologists reached the island in August 2009 only one bat could be detected, flying regularly along certain tracks. It could not be caught and the last time it was heard calling, on 26 August, provides an exact date of species extinction. Bat detectors stationed on the island after that time failed to detect any. The Environment Minister copped criticism in the media for the department’s slow response.
The Christmas Island pipistrelle’s demise in 2009 is probably the only extinction in Australia to have made national news. What made the tiny bat newsworthy was a known expiry date: 26 August.
Biologist John Woinarski wrote a heartfelt book, A Bat’s End (2018), about the demise of this species, saying the evidence fitted wolf snakes causing the extinction. He offered a second more complex possibility involving some habitat loss from mining, a cyclone in 1988 that destroyed many roost trees and possibly some bats, yellow crazy ants preventing access to some roost trees, and giant centipedes and black rats operating as predators. In 2017 he led an assessment of extinct mammals that blamed the pipistrelle’s extinction mainly on wolf snakes, centipedes and crazy ants, with a minor contribution from the cyclone (10%) and clearing (5%).
While we can’t bring the tiny Christmas Island pipistrelle back, we can prevent future extinctions with urgent investment and action on invasive species.
Australia has lost about 100 native plants and animals to extinction since colonisation, most of which were mainly due to invasive species. An estimated 27 of those extinctions occurred since the 1960s.
Learn more about some of Australia’s lost animals: