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Episode 181: Simply Splendid Sloths

We have been wanting to release this episode for quite some time. We recorded this in 2019 for our Patreon only subscribers and now are releasing it to the masses. These are just incredible animals that are very unique. We know you will absolutely love this episode on sloths.

Sloth History

By all rights sloths should have gone extinct many years ago but found a way to survive. Sloths first emerged 50 million years ago and began to spread throughout first South America and then North America, following the Great American Interchange.  It is thought environmental conditions during this period selected for ever increasing body size. The researchers speculate this could have been due to the climate or competition with larger species. This gave rise to the Giant Ground Sloth and other sloth species. About 10,000 years ago, 90% of all sloth species went extinct.

Today’s species of sloth are considered the “black sheep” of the family line. They are much smaller and tree dwelling, when many were ground species. Because they lived in trees is why many believe today’s sloths survive. There are two major families of sloths:

Bradypodidae (3 toed)

  • Pygmy three-toed sloth (Bradypus pygmaeus)
  • Maned sloth (Bradypus torquatus)
  • Pale-throated sloth (Bradypus tridactylus)
  • Brown-throated sloth (Bradypus variegatus)

Megalonchidae (2 toes)

  • Linnaeus’s two-toed sloth (Choloepus didactylus)
  • Hoffman’s two-toed sloth (Choloepus hoffmanni)

Sloth Physiology

Both the 2-toed and 3-toed sloths have similar physiology. Much of the difference is size. The 2-toed sloth tends to be larger. Both species tend to live 25 to 30 years in the wild. The oldest known sloth lived to be 43 years.

Sloths have an extremely slow metabolism. Thus, they have evolved to hang upside down to save energy. For animals that run atop branches in trees, it expends energy to balance and navigate. Sloths on the other hand, move slowly and save energy.

Two-toed sloths have relatively large home ranges and consume a varied diet of animal matter, fruit and leaves. By contrast, three-toed sloths have much more limited ranges, and eat only leaves. They have the slowest digestion rates of any mammal and expend very little energy at rest. They will also eat the algae that grows on their fur.  he sloths consume the algae, which is rich in fatty compounds and gives them energy. In addition to being a tasty nutritional supplement, the algae may serve as camouflage against predators from above, such as the Harpy Eagle.

One of the most fascinating facts is that Sloths will actually descend the tree canopy to defecate. This takes an incredible amount of energy and leaves them vulnerable to predators like jaguars. When they defecate, Sloths lose 1/3 of their weight and go to the same spot over and over. Why they do this still baffles scientists. The best guess is, they do this to communicate with other sloths, for such things as reproduction or possibly territory claims.

Sloth Conservation

Of the 6 species of sloths, 4 are labeled as “Least Concern” by the IUCN. Two species are endangered.

The Maned Three-Toed Sloth is classified as Vulnerable as it lives in the dwindling Atlantic Forest in Brazil.

The Pygmy Three-Toed Sloth is classified as Critically Endangered. There is roughly only 500 left in the wild on an island off Panama.


Sloth Conservation Foundation




August 25, 2020
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