Wild Personalities: Brown-Throated Sloth

Get to know this adorable slowpoke

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Family: Bradypodidae

Genus: Bradypus

Species: B. variegatus

Range: The canopy of tropical forests of Central and South America, including: Costa Rica, Honduras, Ecuador, Nicaragua, Panama, Bolivia, Colombia, Venezuela, Peru & Amazonia.

Population: Unknown.

Key Features: Wooly, matted fur and wide-spaced eyes, often with a white stripe on the forehead; brown coloration on throat and head; three tell-tale curved 3 to 4-inch claws on each limb; about 23 inches, 8 to 9 lbs.

IUCN Red List Status: Least Concern, but threatened by habitat destruction

A portrait of a three-toed, brown-throated sloth

Imagine spending much of your day asleep? That’s the leisurely life of a brown-throated sloth. These arboreal mammals spend the bulk of their time hanging around the cecropia tree canopy in tropical places like the Pacaya-Samiria National Reserve in Peru or the cloud forests of Costa Rica. One could say munching leaves is their livelihood. The herbivores even have a special tongue with sharp, backward-directed spines to aid in slicing the thick leaves. What’s more, they have huge intestinal tracts, and a four-chambered stomach filled with bacteria to help them digest the roughage. All this eating is a lot of work, so it makes sense that when brown-throated sloths are not snacking, they are sleeping or just relaxing upside down.

While it may seem that a sloth’s waking hours are pretty monotonous, not sleuthing around has a benefit. Turns out, their stealthy slowness (they only move about 40 yards each day) is what keeps these highly-camouflagued creatures safe from predators. An animal that hangs still is harder to spot than one swinging around. If you're exploring the rainforest, be patient as you search for that sloth photo op. You might have better luck if you look for sloths in sunny spots since they have lower body temperature and love to bask in the warm rays. And you can always rely on the keen eyes of our expert naturalists as they guide you on the adventure. —Text by Yelena Moroz Alpert

Read below for more fascinating facts about three-toed sloths:

Going Green

Brown-throated sloths are naturally greyish brown, but their fur is often tinted green—a result of algae growth on their coat. Not only does it help sloths camouflage in the foliage, it provides essential trace elements and nutrients to help with their sluggish digestion. In exchange, the algae thrive by being closer to the sunshine on the backs of these ray-loving sloths.

Get to Know the Toes

Brown-throated sloths are the most prevalent of the six species—though as many as 80 types of sloths once existed across a 50 million year timeline. Today’s sloth family is divided into three-toed and two-toed sloths. The three-toed, brown-throated sloths fall in the same genus, Bradypus, as the three other three-toes: pale-throated sloths, the critically endangered pygmy sloths and the vulnerable maned sloths. While those claws look like overgrown nails, they're actually finger bones that protrude from their limbs.

In the Swim

Sloths don’t like to walk, but they don’t mind swimming and sometimes plop directly into rivers from their perch on a tree. Maybe it’s because of their long arms, but three-toed sloths swim three times faster than they walk on land. What’s more, they can slow their heart rate and hold their breath as long as 40 minutes underwater.

A brown-throated sloth baby clings to it mother

It Takes a Village

Mama sloths, who produce one baby each year, get help from other sloths as they give birth. As she labors upside down, then welcomes a new baby sloth—either in the lower canopy or on the ground—caring helpers assist by cleaning the mother and the baby, and ensuring that the newborn doesn’t tumble out. Mom then takes care of her offspring for five months, often carrying the baby sloth around her belly, until it can take off on its own.

Photo: Linda Burback

Risky Business

Three-toed sloths, as with all sloths, can lose up to one-third of their body weight when they go No.2. That’s because they only go once a week, thanks to their slow metabolism. But doing their business can be precarious since it’s the only time this tree-loving creature descends to the ground where it's vulnerable to predators. Once at the tree base, the sloth does a little ritual dance before it digs a hole with its hind claws, poops, and then politely covers the mess up with leaves. Before heading back up it does one more dance for good measure.

Unique Necks

Sloths have as many as 10 neck vertebrae that allow them turn their head some 270 degrees. All other mammals, regardless of their size, only have seven. (Manatees, which also bear extra vertebrae, are the one other exception.) Researchers still aren't sure what causes the sloth's anomaly, but the evolutionary mechanism could be linked to their low metabolic rates. One thing’s clear, though, that long, lithe neck comes in handy keeping watch when hanging upside down.