Sloths' Dirty Bum Fur Grows Nutritious Algae

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Sloths have a reputation for laziness, but these easy-going mammals could be the world's best recyclers, suggests a new study that finds the poop of three-toed sloths attracts moths that colonize sloth fur and lead to nutritious "algae gardens," which the sloths eat.

The trees that the sloths live in, the moths, and the sloths themselves all benefit from the unusual chain of events, according to the paper published in the latest issue of the Proceedings of the Royal Society B.

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Lead author Jonathan Pauli of the University of Wisconsin-Madison's Department of Forest and Wildlife Ecology first suspected something unusual was up after watching a David Attenborough video on YouTube called "Mouldy Sloth."

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While footage shows a sloth covered in gloppy green algae and moths, Attenborough says, "Imagine an infestation in a shag carpet on top of a compost heap."

Pauli knew this seeming mess had to be for a reason. He and his colleagues went to San José, Costa Rica, to study three-toed sloths in their native habitat.

Sloths spend most of their time resting or eating in the forest canopy but, once a week, they laboriously -- and at risk from wild dog and cat predators -- descend their trees to defecate, thereby fertilizing the trees, Pauli told Discovery News.

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The researchers determined that the dung harbors dung-eating moth larvae that, as Pauli said, "eats its way out of the waste." Sloths obviously don't have toilet paper, so some waste sticks to their bums. When adult moths emerge from the poop -- both from the forest floor and from the sloth bums -- the moths fly into sloth fur.

But the unusual set of events doesn't end there.

The moths themselves then poop, die and decay. The rather gross mixture, when combined with other organic materials on sloth fur, results in the growth of what the researchers call green "algae gardens."

"Sloths eat the nutritional algae, which contains nitrogen and phosphorous," Pauli said. "It's like pepper on top of sloth waste. The green coloration also provides sloths with camouflage."

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