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Sloth Facts & Worksheets

A sloth is an arboreal, solitary animal that lives in trees, feeds on leaves and moves very slowly.

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Sloths are tree-dwelling Neotropical xenarthran mammals that belong to the suborder Folivora. They are known for their lazy movement and spend most of their life hanging upside down on the trees of tropical rainforests in South and Central America. They belong to the xenarthran order Pilosa, which includes anteaters.

See the fact file below for more information about Sloth, or download the comprehensive worksheet pack, which contains over 11 worksheets and can be used in the classroom or homeschooling environment.

Key Facts & Information

Overview

  • There are six extant sloth species divided into two genera: Bradypus (three-toed sloths) and Choloepus (four-toed sloths) (two-toed sloths). Despite their common name, all sloths have three toes on each rear limb, but two-toed sloths only have two dights on each forelimb.
  • The two types of sloths are from distinct, distantly related families, and their morphology is assumed to have evolved through parallel development from terrestrial ancestors. Aside from the existing species, numerous species of ground sloths (including Megatherium) roamed both North and South America throughout the Pleistocene Epoch. 
  • However, during the Quaternary extinction event, they went extinct some 12,000 years ago, along with other large-bodied mammals in the New World. The extinction coincides with the emergence of humans, although climate change has also been cited as a factor.
  • Previously, the Greater Antilles were home to endemic radiation of Caribbean sloths. They featured terrestrial and arboreal varieties, which became extinct after humans colonized the archipelago 6,000 years ago.
  • Sloths are called by their sluggish metabolism and methodical motions. Sloth, which is connected to slow, literally means “laziness,” and their common names in various other languages (e.g., French paresseux) also indicate “lazy” or something similar.
  • Their slowness allows them to consume a low-energy diet of leaves while avoiding discovery by predatory hawks and cats that hunt by sight. Sloths are nearly powerless on land, yet they can float.
  • The woolly coat has grooved hair that is home to symbiotic green algae that hide and nourish the animal. The algae also feed sloth moths, some of which live entirely on sloths.

Morphology and Anatomy

  • Sloths may grow to be 60 to 80 cm (24 to 31 in) long and weigh between 3.6 and 7.7 kg depending on the species (7.9 to 17.0 lb). The two-toed Sloth is somewhat more significant than the three-toed Sloth. 
  • Sloths have lengthy limbs, rounded skulls, and small ears. Three-toed sloths have short tails measuring 5 to 6 cm (2.0 to 2.4 in).
  • Sloths are one of just a few creatures lacking seven cervical vertebrae. Two-toed sloths have five to seven toes, but three-toed sloths have eight or nine. Manatees, with six, are the only other mammals that do not have seven.

Physiology

  • Sloths have color vision but low visual acuity, and they also have impaired hearing. As a result, they rely on their senses of smell and touch to find food. 
  • Sloths have low body heat: 30 to 34 °C (86 to 93 °F) when active and much quieter when resting.
  • Sloths are heterothermic, which implies that their body temperature changes depending on the environment, often meandering from 25 to 35 °C but susceptible to decreasing as low as 20 °C (68 °F) during inactivity.
  • The outer hairs of sloths’ fur grow opposite that of other mammals. In most mammals, follicles develop toward the extremities. Still, because sloths spend so much time with their limbs above their bodies, their hairs grow away from the extremities to safeguard them from the elements while they hang upside down. 
  • In most cases, the fur contains symbiotic algae that camouflage against aggressive jaguars, ocelots, and harpy eagles. Because of the algae, sloth fur has an ecosystem with several species of symbiotic and parasitic arthropods—sloths abode on various arthropods, including biting and blood-sucking insects like mosquitoes and sand fleas.
  • Sloths have a unique ecosystem of communist beetles, mites, and moths. The pale-throated three-toed Sloth, brown-throated three-toed Sloth, and Linnaeus’ two-toed Sloth are among the sloth species known to host arthropods. Sloths benefit from their association with moths because the moths fertilize the algae on the Sloth, which gives them nutrients.

Activity

  • Their limbs are designed for hanging and gripping, not for weight bearing. Muscle mass accounts for only 25 to 30% of their body weight, and most other animals have the muscle mass that accounts for 40 to 50% of their body weight.
  • Because they can’t walk, their specialized hands and feet have long, curved claws that allow them to hang upside down from trees without effort, and they utilize them to pull themselves around the ground. The arms of three-toed sloths are half as long as the legs.
  • Sloths only move when required and then exceptionally slowly. They typically travel at a speed of 4 meters (13 feet) per minute but may accelerate to 4.5 meters (15 feet) per minute if they are in urgent danger from predators. 
  • While they occasionally sit on top of trees, they typically feed, sleep, and even give birth while hanging from them. Even after death, they sometimes dangle from branches.
  • Sloths may move at a maximum pace of 3 meters (9.8 ft) per minute on land. Two-toed sloths can spread between clusters of trees on the ground better than three-toed sloths. Sloths are speedy swimmers, reaching speeds of 13.5 meters (44 feet) per minute.
  • They can traverse rivers and swim across islands using their long arms to paddle through the water. Sloths may further decrease their already sluggish metabolism and heart rate to less than one-third of routine, allowing them to hold their breath underwater for up to 40 minutes.
  • Wild brown-throated three-toed sloths sleep 9.6 hours a day on average. The two-toed Sloth is nocturnal and is stationary 90% of the time.

Behavior

  • Female sloths cluster more than males and are reclusive animals who seldom come into contact with one another unless during mating season. Sloths come down every eight days to defecate on the ground. Scientists have long questioned the cause and mechanism of this phenomenon.
  • At least five hypotheses have been proposed:
  1. Fertilize trees when feces are placed at the tree’s base.
  2. Cover feces to avoid predation.
  3. Chemical interaction between individuals.
  4. Pick up trace nutrients in their claws, which are then ingested.
  5. Prefer a mutualistic relationship with populations of fur moths.
  • More recently, a new hypothesis has emerged that presents evidence against the previous ones and recommends that all current sloths descend from species that defecated on the ground and that there hasn’t been enough selective pressure to abandon this behavior because cases of predation during defecation are sporadic.

Diet

  • Baby sloths learn what to eat by tasting their mother’s lips. All sloths consume cecropia leaves. Two-toed sloths are omnivorous, with a varied diet of insects, carrion, fruits, leaves, and tiny lizards, and may live in habitats spanning up to 140 hectares (350 acres). 
  • On the other hand, three-toed sloths are nearly totally herbivorous (plant eaters), with a restricted diet of only a few trees’ leaves, and no other animal digests its food as slowly.
  • They have evolved to browse in the trees. Because leaves provide little energy or nutrients and are challenging to digest, sloths have massive, sluggish, multi-chambered stomachs filled with symbiotic bacteria that break down the thick leaves.
  • The contents of a sloth’s stomach can account for up to two-thirds of its total weight in a well-fed sloth, and the digestive process may require a month or more.
  • Three-toed sloths urinate and defecate on the ground roughly once a week, excavating a hole and covering it afterwards. They return to the exact location each time, making them vulnerable to predation. This behavior has been considered mysterious, given the high energy expenditure and hazards involved in the trek to the ground.
  • According to a recent study, moths in the Sloth’s fur lay eggs in the Sloth’s excrement. When the larvae hatch, they eat on the dung; when grown, they fly up onto the Sloth above. 
  • Because they dwell on sloth fur and support the formation of algae, these moths may have a symbiotic connection with sloths. Individual sloths spend most of their time grazing on a single “modal” tree; depositing their excreta near that tree’s trunk may also help nourish it.

Reproduction

  • Pale- and brown-throated three-toed sloths mate seasonally, whereas maned three-toed sloths procreate all year. It is still unknown how pygmy three-toed sloths reproduce. Litters consist of one baby after six months of gestation for three-toed and twelve months for two-toed.
  • Newborns spend roughly five months with their mothers. In rare situations, baby sloths perish from a fall because their mother is unwilling to leave the protection of the trees to collect them. Females typically have one kid each year, although sloths’ low amount of mobility can prevent females from locating males for longer than a year.
  • Sloths are not sexually dimorphic; some zoos have received sloths of the incorrect sex. Due to a lack of full-lifespan research in a natural context, the average lifespan of two-toed sloths in the wild is presently unknown. In human care, the median life expectancy is roughly 16 years, with one individual at the Smithsonian Institution’s National Zoo living to be 49 years old before dying.

Distribution

  • Although their habitat is restricted to Central and South American jungles, sloths thrive there. Sloths are estimated to account for 70% of the biomass of tree-dwelling animals on Panama‘s Barro Colorado Island.
  • Four living species are listed as “least concern.” In contrast, the maned three-toed Sloth (Bradypus torquatus), which lives in Brazil‘s dwindling Atlantic forests, is listed as “vulnerable,” and the island-dwelling pygmy three-toed Sloth (B. pygmaeus) is listed as critically endangered. Due to their reduced metabolism, sloths are restricted to the tropics and employ cold-blooded animal thermoregulation habits such as sunbathing.

Human Relations

  • Most sloth deaths in Costa Rica have been attributed to contact with electricity cables and poachers. Their claws also serve as an unexpected barrier to human hunters; while hanging upside-down in a tree, they are kept in place by the nails and rarely tumble down, even when shot from below.
  • Sloths are marketed as pets due to animal trafficking; however, their specific ecosystem makes horrible pets. The Sloth Institute Costa Rica is well-known for caring for, rehabilitating, and reintroducing sloths into the wild.
  • The Aviarios Sloth Sanctuary also cares for sloths in Costa Rica. It has recovered and released around 130 animals back into the wild. However, a May 2016 story included two former facility physicians harshly critical of the sanctuary’s efforts, accusing it of mistreating the animals.

Taxonomy and Evolution

  • Sloths are part of the superorder Xenarthra, a class of placental mammals thought to have emerged on the South American continent some 60 million years ago. 
  • According to one research, xenarthrans diverged from other placental mammals roughly 100 million years ago. Anteaters and armadillos are also classified as Xenarthra. 
  • The first xenarthrans were forest-dwelling herbivores with strong vertebral columns, fused pelvises, short teeth, and tiny brains.
  • Sloths belong to the order Pilosa’s taxonomic suborder Foivora. These terms derive from the Latin words for “leaf eater” and “hairy,” respectively. 
  • Pilosa is one of the minor orders in the mammals class, with anteaters as its only suborder.
  • Bradypodidae, or three-toed Sloth, has four living species:
  • The brown-throated three-toed Sloth is the most abundant of the living sloth species, found in the Neotropical woods of South and Central America.
  • The pale-throated three-toed Sloth lives in northern South American tropical rainforests. It resembles and is sometimes mistaken for the brown-throated three-toed Sloth, which has a considerably more extensive range. According to genetic data, the two species separated roughly 6 million years ago.
  • The snouted three-toed Sloth is currently exclusively found in southern Brazil’s Atlantic Forest.
  • The highly endangered pygmy three-toed Sloth is only found on the Panamanian island of Isla Escudo de Veraguas.

Evolution

  • The lineage of the two existing sloth genera dates back about 28 million years, with similarities between the two- and three-toed sloths. An example of evolutionary processes in an arboreal lifestyle is “one of the most prominent features of convergent evolution known among mammals,” according to the researchers.
  • The ancient Xenarthra had a substantially more enormous diversity of species with a broader spread than those seen now. Ancient sloths were primarily terrestrial, and some reached elephant-like proportions, as Megatherium did.
  • Sloths evolved in South America after a lengthy period of isolation and spread to several Caribbean islands and North America. Swimming is considered to have led to the maritime distribution of pilosans to the Greater Antilles during the Oligocene, and the megalonychid Pliometanastes and mylodontid Thinobadistes were able to colonize North America around 9 million years ago, long before the construction of the Isthmus of Panama.
  • The latest evolution, which occurred approximately 3 million years ago, enabled megatheriids and nothrotheriids to reach North America as the portion of the Great American Interchange. Furthermore, the nothrotheriid Thalassocnus of South America’s west coast converted to a semiaquatic and, possibly, entirely aquatic marine existence.
  • Thelassocnus first appeared in coastal habitats in Peru and Chile during the Miocene. Initially standing in the water, they developed into swimming animals over 4 million years, becoming expert bottom feeders on seagrasses, comparable to present marine sirenians.

Extinctions

  • Due to the closing of the Central American Seaway, which resulted in a cooling trend in the coastal areas, killing off much of the area’s seagrass and making temperature regulation difficult for the sloths due to their slow metabolism, the marine sloths of South America’s Pacific coast became extinct at the end of the Pliocene.
  • Ground sloths went extinct in North and South America approximately 11,000 years ago, shortly after humans emerged. According to evidence, human hunting may have contributed to the loss of the American megafauna. Ground sloth bones discovered in North and South America suggest that people killed, cooked, and ate them.
  • Climate change caused by the end of the last ice age might have had a role but did not connect, albeit earlier comparable glacial retreats with similar extinction rates. 
  • Meglocnus and other Caribbean sloths persisted until around 5,000 years ago, long after the mainland sloths had gone out, but eventually became extinct when humans conquered the Greater Antilles.

Sloth Worksheets

This is a fantastic bundle which includes everything you need to know about the Sloth across 22 in-depth pages. These are ready-to-use Sloth worksheets that are perfect for teaching students about the sloth, which is an arboreal, solitary animal that lives in trees, feeds on leaves and moves very slowly. They are commonly found in the tropics, mainly in Central and South America. It is known to spend most of its lifetime in trees.

Complete List Of Included Worksheets

  • Sloth Facts
  • Slow, Sleepy and Solitary
  • Trees of Truth
  • Jumbled Vocabulary
  • Three, Two, One
  • Six Sloth Species
  • Sloth Sketch
  • Just Like the Sloth
  • Trivia Talk
  • Save the Sloth!
  • Sloth Appreciation

Frequently Asked Questions

What is a sloth?

Sloths are tree-dwelling Neotropical xenarthran mammals that belong to the suborder Folivora. They are known for their lazy movement and spend most of their life hanging upside down on the trees of tropical rainforests in South and Central America. They belong to the xenarthran order Pilosa, which includes anteaters.

Why is a sloth deemed to be slow?

Sloths are called by their sluggish metabolism and methodical motions. Sloth, which is connected to slow, literally means “laziness,” and their common names in various other languages (e.g., French paresseux) also indicate “lazy” or something similar.

Why are sloths hanging upside-down in trees?

Their limbs are designed for hanging and gripping, not for weight bearing. Muscle mass accounts for only 25% to 30% of their body weight, and most other animals have a muscle mass that accounts for 40 to 50% of their body weight. Because they can’t walk, their specialized hands and feet have long, curved claws that allow them to hang upside down from trees without effort, and they utilize them to pull themselves around the ground.

Where are sloths distributed?

Although their habitat is restricted to Central and South American jungles, sloths thrive there. Sloths are estimated to account for 70% of the biomass of tree-dwelling animals on Panama’s Barro Colorado Island.

What are the four living species of Bradypodidae or three-toed Sloth?

The brown-throated three-toed Sloth is the most abundant of the living sloth species, found in the Neotropical woods of South and Central America. The pale-throated three-toed Sloth lives in northern South American tropical rainforests. The snouted three-toed Sloth is currently exclusively found in southern Brazil’s Atlantic Forest. The highly endangered pygmy three-toed Sloth is only found on the Panamanian island of Isla Escudo de Veraguas.

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