Snakes on a plane are spreading, driving native birds to extinction

27 Sep 2018

A brown tree snake. Image: Firepac/Shutterstock

Snakes on a plane wasn’t just a concept for a movie – it is a deadly reality whereby native bird species are being driven to extinction.

As the Japanese knotweed and the noble false widow spider have shown in Ireland, an invasive species finding itself in unfamiliar lands can cause devastation in its new home.

Now, the scale of destruction left by one of the world’s greatest invasive species – a type of cat-eyed snake called the brown tree snake – has been analysed in great detail on the island of Guam.

In a paper published to the Journal of Molecular Evolution, a team of researchers from the University of Queensland found that the snake has devastated the native bird population on the Pacific after hitchhiking on board an aircraft decades ago. This invasion first began back in World War II when these planes began carrying troops to the island from Australia, unknowingly with some brown tree snake passengers on board.

“The snakes’ impact was so devastating, it now ranks among the worst pests of all time,” said associate professor Bryan Fry of the research team.

An orange and blue Guam kingfisher perched on a branch.

The Guam kingfisher, also known as the Micronesian kingfisher, is an endangered species from the island of Guam. Image: Michael Fitzsimmons/Shutterstock

How the snake spread

Since its first introduction, Guam’s native bird population has plummeted from multiple native species to just three.

Despite the snake’s bite being non-toxic to humans, the venom is 100 times more toxic for birds. “It contains a toxin that’s made up of two smaller toxins joined together, a feature that was believed to be unique to brown tree snakes,” Fry added. “[This] research has revealed that this is not the case and that any cat-eyed snakes belonging to the genus Boiga would have caused similar devastation.”

Cat-eyed snakes first evolved in Africa before spreading across the Indian subcontinent and travelling southward through south-east Asia and then Australia. The researchers believe this rapid spread was bolstered by the power of the snake toxin on non-mammal species.

Rather than being a problem of the past, the researchers fear that little is being done to ensure the snake’s presence is not spread even further. “The US government is still flying military planes from Guam to Hawaii, and the snakes continue to hitchhike,” Fry said.

“They’re regularly intercepted in the Hawaii airports so, if these direct flights are allowed to continue, it’s only a matter of time until they get to Hawaii and wipe out the birds like they did on Guam.”

With a differing view, a spokesperson for the Hawaii Department of Agriculture offered a statement in response to the latest research. “The last live brown tree snake found in Hawaii was in 1994, almost 25 years ago. Although the threat is very real, there is no evidence that brown tree snakes are currently hitchhiking to Hawaii on aeroplanes and the statement that it is a regular occurrence is false.

“The Hawaii Department of Agriculture, US Department of Agriculture – Wildlife Services, the territory of Guam, the US Department of Defense and the US Geological Survey have been working jointly for decades to prevent the transport of brown tree snakes to Hawaii in a multilevel biosecurity programme, which has been highly successful.

“Hawaii does not have any known established snake populations and it is a priority to keep snakes out of the state. Hawaii has the highest number of endangered species and snakes pose a serious threat to this unique ecosystem.”

Updated, 9.09am, 1 October 2018: This article was updated to include a statement from the Hawaii Department of Agriculture.

Colm Gorey was a senior journalist with Silicon Republic