First it was two million snakes. Now spiders are taking over Guam. The tiny island is experiencing a population explosion of arachnids because a vast, invasive army of snakes ate most of the native birds, the spiders' natural predator. Biologists say Guam's jungle currently holds 40 times more spiders than are found on nearby islands. "You can't walk without a stick in your hand to knock down the spiderwebs," says a researcher.
The brown tree snake was originally transported to Guam during World War II, and now millions slither through its terrain. The reptile horde has eaten out of existence 10 of Guam's 12 native bird species. "There's no other place you can look to see what happens when birds are removed over an entire landscape," said a scientist. "Any time you have a reduction in insectivorous birds, the system will probably respond with an increase in spiders."