June 2, 2008

Sloths Not as Lazy as Thought

In a study that illustrates the pitfalls of relying on research done on animals in captivity, biologists found that wild sloths slept far less than they previously thought. Karen Hopkin reports.

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[The following is an exact transcript of this podcast.]

Picture a sloth and what do you see? Some slow-moving, hairy beast, just hanging around, maybe even catching some Zs. And that’s just your husband. Ok, seriously. We’ve all seen films of three-toed sloths, odd-looking creatures that spend their days hanging upside down in the rainforest canopy. They move so slowly that mossy looking algae actually grows on them. And legend has it they sleep like 16 hours a day.

But researchers from Germany and the U.S. have found that sloths might not be the slug-a-beds we think. Using equipment designed to monitor the brain waves of animals in the wild, the scientists found that sloths actually spend less than 10 hours a day asleep in the trees. Their results appear in the current issue of the Royal Society journal, Biology Letters.

Why the discrepancy? Well, the earlier estimate comes from work done with animals in captivity. And maybe in the sloth sleep lab, there’s not much to do besides snooze. In the wild, on the other hand, the animals need to keep an eye open for potential predators, like snakes or birds. And they also spend time foraging for food. Because nobody’s bringing a sloth any breakfast in bed.—Karen Hopkin

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