Earthworm invasion

Beavers reshape landscapes with their dams. Wolves control elk populations. Sea otters protect kelp forests by eating sea urchins. These are what ecologists call "keystone" species: critters that control an ecosystem and ...

Burmese pythons prove elusive prey in Florida challenge

Strapped to Billy Bullard's hip was a machete he'd bought at a yard sale. In his fist were 4-foot-long metal snake tongs. Attached to the tongs was a high-resolution waterproof camera he called a "snake-cam."

The spiralling cost of invasive species

Some aliens arrived as stowaways. Others were brought in deliberately, for fun or profit. And others were so tiny that nobody noticed them until way too late.

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