Why do sloths have green fur?

A recent article on the Guardian website reminded me about how much I like sloths! The articles author, Henry Nicholls, was discussing an engraving of a Pale-throated Three-toed Sloth (Bradypus tridactylus) from 1871 and the early speculation that surrounded the green tinge of sloth fur.

The engraving in question was made by Berthold Seeman, a German botanist who had brought back a specimen from Nicaragua. He had noticed a “greyish-green colour” on his specimen and wondered if it was camouflage. When he further observed that this colour had disappeared from areas of fur that were exposed to light, he concluded that something might be growing on the fur which grew well in the damp, gloomy climate of the forests in which sloths live.

Since then, scientists have discovered that the green growth on the sloth is algae and although its significance is not fully understood, it is likely to have some camouflage qualities and it appears that the sloths eat the algae!

My favourite species of sloth is the Pygmy Three-toed Sloth (Bradypus pygmaeus), possibly because there are some great photos of this species that have been taken by a scientist called Bryson Voirin.

The Pygmy Three-toed Sloth is the smallest of all the sloth species and is listed as Critically Endangered on The IUCN Red List of Threatened Species due its small population size and restricted location. It is found in just one location in the whole world, on a tiny island called Escudo de Veraguas, found off the coast of Panama. Although the island is uninhabited, visitors to the island have removed some of the sloths habitat by cutting down mangrove trees for firewood. The area is now a designated marine reserve and few tourists visit the island.

Luckily for this cute animal, it has been championed for a number of years by the Zoological Society of London’s (ZSL) EDGE of Existence initiative. In 2012 two scientists from ZSL visited Escudo de Veraguas in search of the Pygmy Three-toed Sloth and were delighted to see the population was breeding. You can read their great blogs here!

Last year, an EDGE Fellow began a project which hopes to increase protection and awareness of Escudo de Veraguas and its unique habitat and inhabitants. I hope the project is a success and I eagerly wait to hear more about how the project is progressing!

Get your fix of Pygmy Three-toed Sloth and see footage of one swimming in this great short BBC film!


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