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A brown tree snake

Anthony Wall

1st February, 2006

At dead of night, unseen, a slithering stowaway disembarks from a newly docked ship… down a rope, across the quay and into concealing undergrowth. Is that what happened? Or did the snake hitch a ride on a military aircraft from Indonesia, maybe, to take up residence here on the American island of Guam in the Pacific?

No one can be sure of the details. All we know is that sometime after World War Two – in the late 1940s or early 1950s – this now notorious reptile first insinuated itself into a fresh and ideal habitat. One pregnant female, just one, would have been enough to trigger the population explosion that brought Guam massive economic and ecological headaches.

Boiga irregularis, the brown tree snake, is neither very large nor very venomous. As villains go, it seems almost ‘puny’. And yet its conquest of the island – and much of Guam’s wildlife – is complete. It has wiped out 12 bird species, some of them found nowhere else. A further dozen species of lizard look certain to follow.

Despite all human countermeasures, Boiga irregularis continues to dominate and prosper – at up to 13,000 specimens per square mile.

Guam, a key US base during the war, was utterly unprepared for such an invasion. And island creatures that had evolved thousands of miles from the nearest landmass had never encountered a snake – let alone one that climbed trees and struck in the dark. They were defenceless. A stealthy predator, whip-thin and extraordinarily elastic, the...


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