The accidental introduction of a snake species to Guam several decades ago almost completely wiped out the Pacific island’s forest birds. Now, the lack of birds is causing Guam’s spider population to explode. 

A new study shows Guam’s jungles have 40 times more spiders in the wet season than the jungles of the nearby islands of Rota, Saipan and Tinian, where birds are still around to eat spiders. 

During the dry season, Guam — a U.S. territory about 1,500 miles south of Tokyo and 3,700 miles southwest of Hawaii — had more than twice as many spiders as the nearby islands.