What Do Sloths Eat? Sloth Diet, Food, and Digestion

What Do Sloths Eat? Sloth Diet, Food, and Digestion

  • Sloths are folivores
  • It takes up to 30 days to digest a leaf
  • Ambient temperature affects sloths’ digestion
  • Sloths eat small quantities of leaves per day
  • Sloths have unusual toilet habits

What is a folivore?

A folivore is an animal that specializes in eating leaves. From the Latin folium meaning “leaf” (same root word as foliage) and the suffix -vore, meaning “to eat” or “to devour”, it refers to any animal that exclusively or primarily eats leaves.

 

 

All species of sloths are folivores. The three-fingered sloth eats leaves and occasionally seed pods (like Cacao pods), while the two-fingered sloth has a more varied diet that sometimes includes both seed pods and fruit.

 

sloths chocolate
Three-fingered sloth (Bradypus variegatus) eating a cacao pod.

What kinds of trees do sloths eat?

Sloths as a species eat leaves from over 90 different kinds of trees, however, any given individual usually rotates between half a dozen to a dozen kinds of trees. They inherit these preferences from their mothers.

Sloths are iconically associated with the Cecropia, and indeed these trees are an important part of reforestation programs that help restore sloth habitat. However, sloths need much more diversity in their habitats and diet than this. Montgomery and Sunquist (1975) listed 28 tree species and three lianas used for food by nine Brown-throated sloths (B. variegatus) and Queiroz (1995) listed 16 plant species in a study also carried out with Brown-throated sloths in the Mamirauá Reserve, in the Amazon.

Three-fingered sloths:

  • Cacao pods and leaves (Theobroma cacao)
  • Sangrillo (Pterocarpus officinalis)
  • Cecropia spp.
  • Colorado (Luehea seemannii)
  • Chilamate (Ficus insipida)
  • Sapotaceans (Micropholis venulosa)
  • Fig trees (Ficus spp)
  • Apocynaceas (Mandevilla sp.)
  • Moraceae
  • Euphorbiaceae
  • Bombacaceae

Two-fingered sloths:

  • Bobacaceae flowers
  • Barrigon leaves and  flowers (Pseudobombax septenatum)
  • Liana
  • Espave (Anacardium excelsum)
  • Poró (Cochlospermum vitifolium).
  • Jobo (Spondias spp.)

 

How do folivores digest food?

Trees evolved leaves to collect and process sunlight, not to be eaten, and leaves have very tough cell walls containing large amounts of cellulose. Mature leaves may also contain chemicals that build up over time and make the leaves toxic if eaten in large quantities. Leaves also contain very few calories compared to other food sources, and in order to eat enough leaves to meet their energy requirements, folivores have some unique feeding habits and specialized digestion.

 

 

To avoid toxins and tough cellulose, sloths favor fresh new leaves that typically grow on the end of branches. They move from tree to tree, eating fresh leaves from a variety of sources. This means that any toxins present in one type of leaf are unlikely to build up over time in the sloths’ bodies.

 

Baby two-fingered sloth

 

Sloths do not digest the nutrients from leaves directly. Instead, they have a very complex digestive system that enables bacteria in the sloths’ gut to ferment and break down the leaves; the sloths derive their caloric and nutrient requirements from this gut bacteria.

How does ambient temperature affect sloths’ digestion?

As with most mammals, the gut bacteria of sloths are sensitive to temperature, however, sloths are poikilotherms, meaning that compared to most mammals sloths do not maintain a constant body temperature. Instead, the ambient temperature of the surrounding rainforest determines how warm or cold a sloth is. This is a very efficient evolutionary strategy to help sloths save energy and camouflage them from predators that detect infrared radiation (such as some snakes), but it makes sloths very vulnerable to extreme temperatures.

 

sloth basking
Sloths also bask under the sun / Photo by Cristhian Chentiko

 

If a sloth gets too cold, the bacteria in their gut can die and leave the sloth unable to digest any more food. Even if the sloth warms back up, the bacteria will have been killed off and the sloth could starve to death—even with a full stomach full of leaves. In rescue centers that specialize in rehabilitating wild sloths, emergency probiotics taken from healthy sloths can replenish this gut bacteria and save a cold sloth from starvation.

How much do sloths eat?

Sloths do not eat a large quantity of food on a daily basis. The average dry weight of leaves eaten by any given three-fingered sloth is approximately 73.5 grams (2.5 ounces) per day. This is only one-third of the amount eaten by howler monkeys, which eat many of the same leaves, live in the same habitat, and are about the same size as sloths. Sloths eat slightly more on warmer days, but there is little variation in food intake between individuals, suggesting that sloths’ feeding habits are very well optimized for their environmental conditions.

 

baby sloth eating fruit leaves

 

Sloths drink water

A long-held presumption in ecology is that sloths get all the water they need from the foliage they consume, and few documented observations exist of either of the two sloth genera  (Bradypus and Choloepus) drinking in the wild.

 

sloth drinking water
Male Three-fingered sloths drinking water / Photo: Suzi Eszterhas

Rainforests, in general, are becoming hotter and dryer with global warming. In addition, fragmented forests in urban areas tend to have hotter temperatures in the understory, because of more light penetrating the forest. Dr. Rebecca Cliffe believes that this is making urban sloths need to drink more and travel further to find water.

How do sloth moms feed their babies?

Sloths are mammals, which means that they nurse their young on milk. Baby sloths crawl onto their mother’s stomach immediately after birth and cling to her, suckling small amounts of milk throughout the day. Producing milk is energetically expensive, so sloth moms can’t store much milk–instead, they produce milk on-demand as the baby needs it.

 

sloth mother feeding her baby leaves
Baby sloths learn from their mother what leaves are good to eat / Photo: Suzi Eszterhas

What do baby sloths eat?

Young sloths begin supplementing their diet with leaves as young as one week old. Baby sloths are very curious about what their mother is eating, and they will sample leaves from her mouth as she eats.

 

 

As they do this, they learn which leaves are good to eat and which to avoid, and this early exposure will stay with them throughout their lives. Teaching baby sloths which leaves to eat is a major challenge for rescue centers that seek to raise orphan sloths to return to the wild.

What do captive sloths eat?

Many captive sloths live in zoos far from their native tropical rainforests. This can make getting fresh, natural foliage for sloths’ diets very difficult, and so many organizations will feed sloths whatever plants are available, such as vegetables, including root vegetables and plants from non-tropical climates, which they have not evolved to eat.

 

 

The typical food plate for a two-fingered sloth in captivity consists of boiled carrots, eggs, flowers, celery, green beans, and bananas. This diet has far too much glucose for sloths and can lead to health complications including diabetes and heart disease.

It is theorized that this has a negative impact on sloths’ health and lifespans, however, this will only be confirmed once scientists can better evaluate the lifespans of wild sloths and compare them to sloths living in captivity.

How long does it take sloths to digest leaves?

Sloths digest leaves like they do everything else: slowly. A single leaf can take up to 30 days to pass through the sloth’s digestive tract. Unsurprisingly, this is the slowest digestion rate of any mammal. Humans, for example, digest their food in 24 to 72 hours (1 to 3 days) depending on what kind of food it is, and hummingbirds can complete a digestive cycle in 10 minutes.

 

baby sloth eating leaves

 

Sloths’ digestive systems

Sloths have some very unusual anatomy, and their digestive system is no exception. Of particular note is the fact that a sloth’s esophagus has a loop in it; instead of connecting in a direct line from the mouth to the stomach (as in humans), it forms a loop like a roller coaster. This helps any swallowed food stay in the stomach while the sloth hangs upside down in the trees.

 

 

Their unusual esophagus keeps sloths’ food in their large, four-chambered stomachs no matter what. A sloth cannot vomit, belch or even fart, so it is very important that they do not eat anything bad for them or anything that produces excess gas.

 

Image from the paper: Sloths (Bradypus variegatus) as a polygastric mammal (Ellen Y. E. Mesquita,Paola C. Soares,Luise R. Mello,Elisa C. B. Freire,Ana R. Lima,Elane G. Giese,Érika Branco)

 

Some amount of gas is produced from the gut bacteria as part of the digestion process; this gas is diffused into their bloodstream and carried away to be slowly expelled through the lungs or skin. Sloths’ large stomachs also act as a floatation device when the sloths must swim across rivers to reach new territory.

 

Image: Catriona Gibb

 

Are sloths geophages?

Geophagy is when animals intentionally eat earth or soil, including clay, chalk, or termite mounds. Two-fingered sloths have sometimes been known to eat dirt from the ground, which is a far cry from their usual diet of leaves from the sky! Animals may do this to aid in digestion, absorb toxins, or access nutrients not found in their usual diet. It is thought that the sloths engage in geophagy to supplement nutrients and minerals that are sometimes not available in leaves. 

 

How are sloth toilet habits unusual?

Sloths are very particular about how and when they go to the bathroom. Although they live in the canopy, they travel all the way to the forest floor to poop. Wild sloths defecate approximately once per week, and they can poop out as much as 30% of their body weight when they do.

 

 

Sloths’ pooping ritual involves climbing down to the base of a tree, doing a special “poop dance” that includes wiggling their rear end back and forth, and in the case of three-fingered sloths, digging a small hole with their tail to poop in. Two-fingered sloths do not have tails and skip this step. When they are finished, the sloth climbs back up the tree and resumes hanging out in the canopy. Sloth feces is rich with nutrients and makes an excellent fertilizer for the trees they inhabit.

 

Do sloths eat the algae that grows on them?

Sloth fur is a miniature, mobile ecosystem that the sloths carry around with them. Fed by rainwater, algae grows on the hair, moths reproduce in sloth feces and then migrate back to a sloth to begin the life cycle over again. It was once speculated that these verdant green algae acted as a kind of garden, fertilized by moths, that the sloths would eat (from themselves and each other), supplementing their diet with nitrogen and phosphorous.

 

Photo: Suzi Eszterhas

While sloths groom their fur daily, they do not lick their fur like a cat would, and they are not social animals and do not engage in social grooming. The algae grow in specialized cracks in the sloths’ fur and are not found in sloths’ digestive systems, suggesting that they do not consume it. Additionally, there is no evidence suggesting that the algae feed off of moths or their byproducts.

The role of sloth moths and how they benefit the sloths is not well understood, and much more research is necessary to understand the details and unique nature of the sloth fur ecosystem.

-Rebecca Cliffe