The extinct mammals were about five times larger than a grizzly bear–and filled caves with their poop.

A new fossil and DNA analysis traces how dozens of sloth species responded to climate shifts and humans. Just two small tree-dwelling sloths remain today.

Grizzly 399’s world shrunk. Slowly, year by year, she had to make adjustments to the sprawl and greed of Jackson Hole.

Most of us are familiar with sloths, the bear-like animals that hang from trees, live life in the slow lane, take a month to ...