Brown-throated Three-toed Sloth (Bradypus variegatus)
3-toed Sloth, Brazil, Sept 2000 - click for larger image Ubatuba, São Paulo, Brazil
September 2000

The Brown-throated 3-toed Sloth is the most common and widespread of the family being found from Honduras to northern Argentina. They weigh over 4 kilos and are strictly tree dwellers descending to the ground only to defecate every 2 to 8 days. (Note that, while 2-toed sloths have 2 toes on their fore limbs they have 3 toes on their hind limbs.)

Their diet consists entirely of leaves so they are restricted to areas of evergreen (mainly Cecropia) forest.

3-toed Sloth, Brazil, Sept 2000 - click for larger image Because of this diet, 3-toed Sloths have a compartmentalised stomach and the leaves are broken down by fermentation in both the stomach and the intestines. The stomach and its contents weigh up to a third of the sloth's total weight. As an adaption to the low nutrient content of the leaves, sloths have a low metabolic rate and a low body temperature.

For this reason they favour the crowns of trees that receive the sun so that, when resting, they can regulate their body heat by moving in and out of the sun.

3-toed Sloth, Brazil, Sept 2000 - click for larger image Mind you, they move so slowly that it is difficult to tell when they are resting and when they are not.

Another of the results of their slow movement is that their backs are covered with algae. This is a symbiotic relationship since the algae flourish in the forest humidity while the sloth benefits from the camouflage that the algae provide. The sloth's fur is also home to small moths.

There is an illustration in Eisenberg, Plate 2.
There is further information and more photos at the following web sites:
The Sloth Website
The University of Michigan

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