Brown-Throated Sloth: Three-Toed Sloth Facts, Diet and Habitat

What does a brown-throated sloth look like?

The brown-throated sloth has a small, rounded head, a blunt nose and tiny ears hidden in its fur. Its face is pale with a dark stripe running back from each eye, which gives it a permanent “smiling mask” look. The throat, forehead and sides of the face are dark brown, the feature that gives the species its name.

The body fur is grayish-brown to beige, made of a soft underfur and a long, coarse outer coat. The outer hairs are full of tiny cracks where algae grow, so many sloths look greenish, especially in wet forests.

Adult males are easy to tell apart from females. They have a patch of short orange or yellow fur between the shoulders with a black stripe through the middle, called a speculum. Females lack this patch.

All three-toed sloths have three long, hooked claws on each foot. On the front feet of a brown-throated sloth they reach about 7–8 cm (2.8–3.1 in). The arms are much longer than the legs, and the animal has extra neck vertebrae, which let it turn its head up to about 270 degrees without moving its body.

How big is a brown-throated sloth?

Brown-throated sloths are about the size of a large house cat, but much lighter than they look under all that fur.

Males and females are about the same size. A large part of an adult’s weight is food: leaves fermenting in its big, many-chambered stomach, plus a week’s worth of droppings and urine waiting for the next trip to the ground.

Habitat and range

The brown-throated sloth lives from Honduras in the north through Nicaragua, Costa Rica and Panama, and across northern and western South America to Venezuela, Colombia, Ecuador, eastern Peru, Bolivia and much of Brazil. It once lived in northern Argentina but is now thought to be extinct there. North of the Amazon and east of the Rio Negro it is replaced by its close relative, the pale-throated sloth (Bradypus tridactylus).

It is a forest animal, found in evergreen rainforest, semi-deciduous and dry forest, and swamp forest. It also survives in disturbed landscapes such as cacao plantations, riverside strips of forest, living fence lines and even village gardens, as long as there are enough trees. Most live from sea level to about 1,200 m (3,900 ft), with a few records higher up.

Brown-throated sloths have tiny home ranges. Depending on the forest, one sloth may use just 0.5–9 hectares (1–22 acres), and within that area it may rely on a few dozen favorite trees.

What does a brown-throated sloth eat?

The brown-throated sloth is a strict herbivore and a specialist leaf-eater, or folivore. It eats young leaves, buds and shoots from many kinds of trees and vines, along with some flowers and fruit. Trees of the genus Cecropia, fast-growing trees common at forest edges, are especially important in many areas, and their open crowns also make sloths easier for people to spot.

Each sloth has its own favorite trees, and young sloths learn which leaves to eat by licking food from their mother’s mouth. Leaves are poor in energy and full of tough fiber and plant toxins, so sloths digest them slowly with help from bacteria in their stomach. A single meal may take days to weeks to pass through the gut. Sloths get almost all their water from leaves and drink only now and then.

Behavior: life in the slow lane

Everything about the brown-throated sloth is built around saving energy. It has a resting metabolism roughly half of what would be expected for a mammal of its size, and its body temperature usually sits at about 30–34 °C (86–93 °F), several degrees lower than most mammals. Muscles make up only about a quarter to a third of its body weight. In trees it typically moves at about 0.24 km/h (0.15 mph), a few meters a minute. The reasons are explained in why are sloths so slow?

Like a lizard, a sloth warms itself by basking. Brown-throated sloths often choose trees with sunny crowns and sit in the morning sun before feeding. Unlike two-toed sloths, which are mostly nocturnal, they can be active at any hour of the day or night, usually in short bouts.

Adults are solitary and quiet. They mostly communicate through scent and through droppings left at the base of trees. Fights are rare, though males have been seen hooking at each other with their front claws.

Hanging upside down is effortless for a sloth. Its claws work like hooks, and its stomach and liver are attached to the lower ribs, so their weight does not press on the lungs while the animal hangs.

Weekly trips to the ground

About once every three to eight days, a brown-throated sloth climbs down its tree, digs a shallow hole with its stubby tail, empties its bowels and bladder, covers the spot and climbs back up. This is the most dangerous part of its week, because a sloth on the ground is slow and exposed. Scientists still debate why three-toed sloths take the risk; see how often do sloths poop?

A good swimmer

On the ground a sloth can barely walk and drags itself forward with its arms. In water it is a different animal. Brown-throated sloths swim well with long, steady arm strokes and cross rivers and flooded forest, and they move faster swimming than crawling. Read more in can sloths swim?

Reproduction and life cycle

Brown-throated sloths can breed at different times of year, although in some areas most mating happens during particular months. A female ready to mate gives a loud, high-pitched cry to attract males. After mating the male leaves, and the female raises the young alone.

Gestation lasts about six months, with reported values from five to eight months. The single baby is born fully furred, with working claws, and weighs well under 1 kg (2.2 lb). For the first months it clings to its mother’s belly and starts tasting leaves within days of birth, picking up her food preferences.

The young sloth stays with its mother for about five to six months. Then she moves away and leaves it part of her home range, an unusual way of handing over a ready-made territory. Females usually breed for the first time at about three years old and males at three to five years, and a healthy female can have one young a year.

How long do brown-throated sloths live?

Nobody knows exactly. Few wild sloths have been followed for their whole lives, and three-toed sloths have historically done poorly in zoos because of their specialized diet, so captive records are scarce. Published estimates for wild three-toed sloths range from about 20 to 30 years, and some sources suggest longer. Two-toed sloths, which adapt far better to captivity, have lived for more than 40 years in zoos.

Predators and threats

Natural predators include jaguars, ocelots and other wild cats, large snakes such as boas, and big forest raptors, above all the harpy eagle. Spectacled owls and other large owls may take young sloths. The sloth’s main defense is simply not being noticed: it moves so little, and its algae-tinted fur blends so well with the canopy, that it looks like a clump of dead leaves or a termite nest.

Humans are now a bigger threat in many places. Clearing forest for farms, roads and towns breaks up the canopy, forcing sloths to cross open ground or roads. Many are hit by cars, electrocuted on power lines they use as bridges, or attacked by dogs. Others are taken from the wild for the illegal pet trade or for tourist photos, which is stressful and often fatal for the animals.

Conservation status

The brown-throated sloth is listed as Least Concern on the IUCN Red List (assessed 2014). It has a huge range, occurs in many protected areas and copes better with disturbed forest than many rainforest mammals. Trade in the species is regulated under CITES Appendix II.

Its close relatives are not all so lucky. The maned sloth of Brazil’s Atlantic Forest is listed as Vulnerable, and the tiny pygmy three-toed sloth, found only on one small island off Panama, is Critically Endangered.

Myths and facts

Myth: sloths are lazy. Their slowness is an energy-saving strategy that suits a diet of leaves, not laziness. The English word “sloth” comes from an old word for slowness or laziness, and the same idea appears in the Spanish perezoso and the German Faultier.

Myth: sloths sleep 20 hours a day. That figure came from captive animals. Wild brown-throated sloths studied in Panama slept about 9 to 10 hours a day; see how long do sloths sleep?

Fact: a sloth is a walking ecosystem. Its fur holds algae, fungi, mites, beetles and special sloth moths, some of which are found nowhere else.

Relationship with people

Sloths are among the most popular animals of Central American tourism, and spotting one in Costa Rica or Panama is a highlight of many trips. The best way to enjoy them is with binoculars and a local guide, keeping a respectful distance. Wild sloths should never be touched, held or used as photo props, and baby sloths found alone on the ground should be reported to local wildlife authorities or a licensed rescue center rather than picked up. The difference between this species and its two-toed neighbors is explained in two-toed vs three-toed sloth.