Sloths are found throughout Costa Rica’s tropical forests. (Photo credit: Kjersti Joergensen/Shutterstock)

With their shy, seemingly secret-hiding smiles, languid movements, and unique habits, the sloth fits the basic description of a charismatic animal to a T.

These unusual animals can be found in the tropical forests of Central and South America. Their populations are flourishing in their Costa Rican habitat. Sloths can be found in ecosystems throughout this Central American country, except at the highest elevations.

There are two species of sloth found in Costa Rica: Bradypus variegatus, commonly known as the three-toed sloth, and Choleopus hoffmanni, commonly known as the two-toed sloth. Both of their scientific names reflect their slow movement, as Bradypus means “slowness of foot,” and Choleopus means “lameness of foot.” Though they look similar to primates, sloths are actually more closely related to anteaters and armadillos.

Though it was commonly thought that sloths spent most of their time sleeping–previous estimates had sloths spending upwards of 14 hours asleep per day–research from 2008 indicates that these animals actually only sleep 9 to 10 years a day. Scientists think the previous estimates, based on captive populations, overestimated the sloths’ sleep patterns as those sloths lacked the need to be vigilant against predators. In the wild, three-toed sloths are active both day and night, while two-toed sloths are nocturnal.

These animals spend the majority of their lifetimes in the tops of trees. Their slow movement is likely a result of their need to conserve energy due to their extremely slow metabolism. It takes a sloth up to four weeks just to digest a single leaf. Contrast that with humans, who completely digest a meal within a period of 24-44 hours. One of a sloth’s more unique habits is a result of its slow digestion–sloths only relieve themselves once a week. To do so, they climb down to the bottom of the tree where they do their business, losing about 1/3 of their body weight in the process.

One thing that helps sloths avoid predators and blend in with their leafy habitat is the algae that grows on their fur. The species of algae that lives within sloth fur is Trichophilus welckeri, which is found nowhere else. Research indicates that the algae is passed from mother to offspring within a few weeks of its birth. However, a sloth’s fur isn’t just a habitat for algae. It also houses a variety of other insects and fungi. One of the more interesting examples is the pyralid moth (Cryptoses spp.), which relies on the sloth for its entire lifecycle. A sloth’s body could be home to more than 100 moths. The moth spends the majority of its lifetime burrowed deep within the sloth’s fur. The real magic happens when the sloth descends to the base of its tree to do its weekly business. The moths are coprophagous, meaning they eat excrement. Female moths lay their eggs in the sloth’s excrement, and the larvae grow to maturity within the dung before hatching and flying up the tree to find another sloth’s furry back to inhabit.

According to reporting in The New York Times about this phenomenon, “After [the moths] die, their bodies are decomposed by the host of fungi and bacteria in the sloth’s fur. The metabolic products of this decay, especially nitrogen, are the feedstock for the specialist algae that grow in the sloth’s hair shafts. The researchers guessed that the sloths might be eating the algae from their own fur, and that this could be the purpose of the whole system.”

In addition to being unique animals, it appears that the sloth itself is home to a unique ecosystem as well.

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