Mistaken Identities: Two-Toed vs. Three-Toed Sloths

Did you know there's more than one species of sloth? Sloths are known for their fur, living in trees and, of course, being slow. But not every sloth moves as slowly as you might think. Seven species of sloths are native to Central and South America and can be divided into two families: two-toed sloths (two species) and three-toed sloths (five species).

When you think of a stereotypical slow sloth, you're probably thinking of a three-toed sloth. They have super slow metabolisms and spend most of their day hanging around the rain forest canopy, only coming down when they need to poop or find a mate. Two-toed sloths, however, can move quickly when they want to. Their slightly faster metabolism lets them move throughout the day with bursts of energy. In fact, guests visiting the National Aquarium can often see the Linne's two-toed sloths in our Upland Tropical Rain Forest exhibit climbing around right above their heads!

Plenty of other differences set two-toed and three-toed sloths apart. Learn about these animals and then visit the Aquarium to see two-toed sloths in action!

Other Differences

Differences in noses, claws and necks are visual differences that are easy to see, but there are other ways to tell two-toed and three-toed sloths apart.

Teeth

Different lifestyles call for different teeth. Two-toed sloths have two pairs of razor-sharp pseudo-canines in the front of their mouth. They use these for defense and eating. On the other hand, three-toed sloths only have flat teeth, which they use to eat leaves.

Sloth Moths

Sloths have thick fur that absorbs moisture and grows green algae, which provides camouflage and attracts sloth moths. Adult sloth moths live in sloths' fur and lay their eggs in sloths' droppings. Once they're grown, the moths find a sloth to live with. While both kinds of sloths have a relationship with sloth moths, they tend to hang around more on three-toed sloths. Two-toed sloths move faster and more often than three-toed sloths, making them a less desirable habitat.

Diet

Two-toed sloths eat a variety of food, such as veggies, fruit and leaves. At the Aquarium, staff preparing food for the sloths cut vegetables into thick wedges to make them easier to grab. On the other hand, three-toed sloths have a much less varied diet. They eat leaves from only a few tree species, like cecropias. Due to the differences in their metabolism and diet, two-toed sloths may poop up to two to three times a week, while three-toed only poop once every seven to 10 days.

Lineage

Three-toed and two-toed sloths aren't related! Despite their similar appearances, they have no common ancestors. Tens of millions of years ago, before sloths lived in trees, they lived on the ground, and dozens of species roamed the Americas. While both two-toed and three-toed sloths are descended from giant ground sloths, they don't come from the same group. Sloths are a great example of convergent evolution, which occurs when unrelated species develop similar traits because they live in similar environments.

Safeguarding Sloths' Future

Despite their differences, two-toed and three-toed sloths face similar threats. Throughout Central and South America, deforestation harms sloth populations, and cars and power lines can be lethal. Surprisingly, they are also among the most trafficked animals in the United States.

To help protect sloths, the National Aquarium began participating in the Association of Zoos and Aquariums' (AZA) sloth Species Survival Plan® (SSP) program over 15 years ago. Today, Deb Dial, the assistant curator of Australia: Wild Extremes and Upland Tropical Rain Forest, coordinates the entire program. This plan monitors genetic diversity to ensure the sustainability of the breeding program with AZA-accredited institutions. Support our work by donating today to help sloths and other animals in our care.