R Sloths Endangered

Written by and illustrations created by Lilia Robinowitz, TREE Foundation Summer 2020 Intern, Williams College Class of 2022

1. How many species of sloths are there?
   Six: Pygmy three-toed sloth (Bradypus pygmaeus), Maned sloth (Bradypus -*torquatus), Pale-throated sloth (Bradypus tridactylus), Brown-throated sloth (Bradypus variegatus), Linnaeus’s two-toed sloth (Choloepus didactylus), Hoffman’s two-toed sloth (Choloepus hoffmanni)! There are two-toed sloths (Bradypodidae family) and three-toed sloths (Ai family). Both types of sloths have three toes on their hind limbs, but two-toed sloths have two toes on their front limbs, and three-toed sloths have three. One noticeable difference is that three-toed sloths are slightly smaller than two-toed sloths.
2. Why are sloths so slow?
   Sloths have a very low metabolism, meaning that they convert food to energy very slowly and thus move slowly to expend less energy.
3. How far can they travel in a day?
   On average travel 41 yards/day, which is about half of a football field! Their maximum speed is two meters per day.
   
4. Why do sloths leave the sheltered canopy and go to the ground?
   Every 4-8 days, both two-toed and three-toed sloths come to the ground to urinate and defecate! Sloths leave the comfort of the canopy and expose themselves to the dangers of the ground to go to the bathroom. On the ground, there is a much greater risk of predators, so there is assumed to be some evolutionary benefit to coming to the ground to defecate, but it remains unknown.
5. What do sloths eat?
   Primarily, sloths eat leaves, twigs, buds. Because sloths don’t have incisors, they smack their firm lips to trim leaves. Throughout sloths’ entire lives, their teeth grow continuously, but they never get too long because they get worn down by chewing on leaves. While sloths are mainly herbivores, some sloths supplement their diets with insects and birds occasionally.
6. How much food do they consume?
   Compared to other similarly sized mammals, sloths eat relatively little food because of their low metabolic rate. It can take up to 30 days to digest just one leaf!
7. For how long do sloths sleep?
   Sloths in captivity sleep 15-18 hours a day, and sloths in the wild sleep 10 hours a day — comparable to humans! However, unlike humans, sloths sleep in periods of less than one hour throughout the day and night, disrupted by feeding, scratching, and crawling.
8. Can sloths swim?
   Sloths are great swimmers! While their long limbs function clumsily on the ground, they glide through the water and propel the sloth forward, moving three times faster than on land.
   
9. Why are sloths so difficult to spot in the canopy?
   Sloths are camouflaged by the blue-green algae that grows on the grooves between their coarse hair. The algae helps disguise the sloth among the trees, and the sloth provides the algae shelter and water — a symbiotic relationship. The algae creates a unique ecosystem where other organisms live, too.

   Sloth Illustration by Lilia Robinowitz

10. What’s special about sloths’ body design?
    • Organs are attached to their rib cages — Sloths spend 90% of their lives hanging upside down, so this structural adaptation enables them to breathe normally when hanging upside down and is essential to their survival. Their fur parts on their bellies rather than their backs because they spend so much time upside down.
    • Multi-compartment stomach — This allows them to digest the tough cellulose they consume, although this is a slow process.
    • Extra vertebrae in their neck — They can turn their heads on a 270 degree axis, allowing for a viewing range that is nearly 360 degrees. This acts as an effective defensive mechanism.
    • Can hold breath for 40 minutes — They can suppress their metabolism to decrease their heart rate 1/3 of its normal rate, allowing them to hold their breath longer.
    • 25–30% muscle mass — Other mammal species are 40–45 % muscle, but sloths’ body mass makeup allows for up to 30% of a sloth’s body weight to consist of food in the stomach and urine because they have a lower percentage of muscle mass.
    • Low and variable body temperature — Unlike other homeothermic mammals, sloths do not rely on their metabolism to keep them warm. They spend less energy on thermoregulatory processes that require a lot of energy to be spent. Their low body temperature varies over 10 °C in accordance with the ambient temperature and sunlight exposure.
11. What threats do sloths face?
    Sloths are threatened by habitat loss. Sloths live in and rely on the rainforests but deforestation in Central and South America has destroyed their habitats. Sloths are also hunted for food and traditional medicinal functions. The predators of sloths are large felids, eagles, and, for the three-toed sloth (Bradypus variegatus), the spectacled owl (Pulsatrix perspicillata) is suspected to be a predator as well.
12. Are sloths endangered?
    Yes, the maned sloth (Bradypus torquatus) of Brazil is listed as vulnerable by the IUCN Red List, and the pygmy three-toed sloth (Bradypus pygmaeus) of Panama is critically endangered. The maned sloth is challenged by habitat loss because of resort building and urban development. The pygmy three-toed sloth faces hunting pressures and its range is restricted to one small island which both threaten its existence.
13. How do sloths mate?
    Like most aspects of the sloth’s life, mating and giving birth occur in the trees. When ready to mate, the female sloth yells a shrill monoton scream, and the males in the area answer. If there are multiple male sloths in the area ready to mate, the suitors fight against one another for the female (sometimes violently) while hanging from the trees.

A question I get asked often is “Are sloths endangered?”. While the sloths of Costa Rica may not be categorized as ENdangered, they are still very much IN danger. Every day critical habitat is destroyed and sloths are injured by human encroachment. They can’t run across roads, jump through gaps in the forest or fend off dogs. FWS's Threatened & Endangered Species System track information about listed species in the United States.

Where Sloths Live:

• Pygmy three-toed sloth (Bradypus pygmaeus) – off the coast of Panama island of Escudo de Veragua
• Maned sloth (Bradypus torquatus) – Eastern Brazil
• Pale-throated sloth (Bradypus tridactylus) – Guyana, Suriname, French Guiana, eastern Venezuela and Brazil north of the Amazon River.
• Brown-throated sloth (Bradypus variegatus) – neotropical ecozone of Central and South America
• Linnaeus’s two-toed sloth (Choloepus didactylus) – Venezuela, the Guyanas, Colombia, Ecuador, Peru, and Brazil north of the Amazon River.
• Hoffman’s two-toed sloth (Choloepus hoffmanni) – Central America and northern South America, including portions of Peru and Central Brazil

References

Are Sloths Endangered Species

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