How Long Do Sloths Live? Sloth Lifespan in the Wild and Zoos

How long do sloths live in the wild?

The honest answer is that nobody knows exactly. Sloths are hard to follow: they live high in the canopy, move very little, blend into the leaves and, in the case of two-toed sloths, are mostly active at night. Few research projects have tracked individual sloths from birth to death.

What scientists have are pieces of the puzzle, such as radio-tracking studies in Panama and Costa Rica that have followed individual adults for several years, plus what is known about their slow growth and breeding. Based on this, wild three-toed sloths such as the brown-throated sloth are usually estimated to live about 20 to 30 years. Estimates for wild two-toed sloths are even less certain; some sources give figures as low as about 12 years, others similar to three-toed sloths.

How long do sloths live in zoos?

Two-toed sloths do very well in captivity. They eat a wide variety of plant foods, adapt to zoo routines and face no predators. Zoo records show many living 20 to 30 years, and Hoffmann’s two-toed sloth has been reported living to about 43 years. Several other two-toed sloths in European and North American zoos have been reported in their 40s, with a few claims of close to 50 years. For animals caught in the wild decades ago, though, the exact birth year is usually an estimate.

Three-toed sloths are a different story. They feed on the leaves of a limited set of rainforest trees, and those leaves are hard to supply outside the tropics. As a result, very few zoos keep them, and captive three-toed sloths have historically had short lives. Their wild estimate is therefore based on field studies, not zoo records.

Why do sloths live so long?

Sloths fit a pattern seen in many slow-living animals: a low metabolism, slow growth and slow reproduction tend to go with a long life.

• Low energy use. Sloths burn energy at roughly half the rate expected for a mammal of their size, and their body temperature changes with the weather. Read more in why are sloths so slow?.
• Staying hidden. A sloth that barely moves and is tinted green by algae is hard for a predator to spot. Fewer attacks means more adults survive to old age.
• Slow breeding. A female three-toed sloth usually has one baby a year at most, and a two-toed sloth even less often after a pregnancy of about 11.5 months. Species that breed this slowly can only survive if adults live a long time.
• Tough bodies. Two-toed sloths in particular are known to recover from injuries that would kill many other mammals of their size.

The riskiest time: the first year

Most sloth deaths probably happen early in life. A baby sloth clings to its mother for several months, and if it falls it may not be rescued. Young sloths that have just left their mothers are inexperienced and more exposed to predators.

The main natural predators are the harpy eagle, which plucks sloths from the canopy (see what do harpy eagles eat?), large cats such as jaguars and ocelots, and big snakes. Sloths are also most vulnerable when they climb down to the ground, which they do about once a week to defecate.

Human threats that shorten sloth lives

In many places, people now cause more sloth deaths than predators do:

• Power lines. In Costa Rica, sloths often use power lines as bridges between trees and are electrocuted. Rescue centers treat many burned sloths each year, and some towns now insulate cables or build rope canopy bridges.
• Roads. Sloths crossing on the ground move very slowly and are easily hit.
• Dogs. Domestic dogs attack sloths on the ground near towns and farms.
• Forest loss. Clearing breaks up the canopy, forcing sloths to travel more on the ground.
• The pet and photo trade. Young sloths taken from the wild for pets or tourist photos often die quickly from stress and poor diet.

Myths and facts

• Myth: sloths die from moving too slowly. Fact: slowness is an energy-saving strategy and a form of camouflage, not a weakness that shortens their lives.
• Myth: sloths can live 50 years in the wild. Fact: there is no wild record anywhere near that. The longest documented lives come from zoos.
• Myth: all sloths do well in zoos. Fact: two-toed sloths do, but three-toed sloths are specialist leaf-eaters that are very hard to keep.

Both species studied here are classed as Least Concern by the IUCN. Protecting forest corridors and making power lines and roads safer are the best ways to help wild sloths reach old age.