Sloths: A Unique Mammal of the Neotropics

This topic submitted by Laura Wigren ( wigrenln@yahoo.com) at 2:35 AM on 5/19/06.

A swim in a tropical stream, Corcovado Natl Park.

Tropical Field Courses -Western Program-Miami University



Laura Wigren
5/10/06
Costa Rica Paper

Sloths: A Unique Mammal of the Neotropics

There are two different genera of sloths, the three-toed sloths (Bradypus) and the two-toed sloths (Choloepus), with a total of five different species that are all geographically restricted to the New World tropical rainforests (Goffart, xv). The differences between the two genuses of sloths extend beyond having two or three claws on their forelimbs. One of the major differences is that three-toed sloths have nine vertebrates, while two-toed sloths have only six or seven vertebrates (Goffart, xv). In addition, the three-toed sloth has a small tail and is more active during the day. The two-toed sloth does have larger eyes, a shorter neck, and moves more frequently between trees. However, the two-toed sloths are seen less frequently because they are typically active at night (Montgomery, 151). Costa Rica, has examples of both genera residing in its rainforests, the Brown Throated three-toed sloth (Bradypus variegetus) and Hoffman’s two-toed sloth (Choloepus hoffman), (Baker).
Sloths are named after their slow movement ability and in almost every language these animals have deemed lazy. The French word for sloth is paresseux and the Spanish word is Perezeso, both of these words translated to English mean “laziness” or “indolence” (Gould, 19). These unique mammals live in the middle and top layers of tropical rainforests and are almost completely arboreal. They have short bodies with long limbs and their heads are capable of rotating over ninety degrees. Their bodies are covered with thick fur that helps to insulate the sloth’s body temperature. Unlike most mammals, sloths have a difficult time regulating their body temperatures. At night their body temperature can drop almost to the surrounding temperature of their environment (infocostarica). The sloths body temperature may be one explanation for why sloths move at such a slow rate. Their slow movement might be a mechanism to help them maintain a higher body temperature (Gould, 20). The sloths fur is also covered in green algae, which helps the mammals to camouflage into the tree top environment. These mammals are herbivores that feed on the leaves of the forest canopy and lack any true canines or incisors. It is a myth that they only feed on cecropia trees, but they do feed almost entirely on leaves (infocostarica). Their unique large stomachs are ruminant like with multiple chambers that are capable of digesting the fibrous leaves (Baker). However, their digestion system is extremely slow and the food can remain in their stomachs for up to a week.
As previously mentioned sloths are almost completely arboreal creatures and can actually sleep up to eighteen hours a day up in the trees (Reebs, 18). They are able to hold onto the trees by hooking their large curved claws on their feet to the branches. While sloths do hang upside down from the tree branches, they sit up while they are sleeping. It is suggested that they sleep upright to help with the digestion process. This is because gravity helps to allow the smaller denser pieces of material sink to the bottom of the stomach and become properly digested (Reebs, 18). The only time sloths descend from the trees is to go to the bathroom. Typically once a week a sloth will climb down from a tree, dig a hole in the ground with their hind limbs and relive themselves, then cover up the hole with leaves. The tiny moths that live in the fur of the sloths also capitalize on the sloths fecal matter by laying eggs in it (Kricher, 126-127). When the larvae hatch they feed on the feces and then the adults go to find a sloth of their own. The moths benefit from this relationship, but for the sloths there is neither a positive or negative impact on their body or health (Kricher, 127).
Male and female sloths generally reach sexual maturity at three years of age (infocostarica). The female will give birth about once a year and has a gestation period of six months (Baker). For the first six to nine months the baby clings onto the mother, typically on her chest. After this period the mother leaves her baby sloth and moves to another tree region. This allows for less competition between the mother and the child.
While sloths are extensively hunted by humans for their meat, humans are not the sloths biggest predator. It is very difficult for humans catch sloths because they make very few sounds and live high up in the forest canopy. However, large eagles, like Harpy Eagle have a great view of the sloths from the air, especially when the sloths venture to the top of the canopy to soak up the sunrays (infocostarica). Another main predator to sloths is the jaguar. The sloths only defense against eagles and jaguars is to slash at them with their sharp claws, because they are not capable of moving away from their predators (Gould, 20).
The biggest threat to sloths is not eagles, jaguars, or being hunted by humans, but habitat fragmentation and destruction of the tropical rainforests. While the species levels for the various types of sloths vary between the five different species, they are all in future danger of becoming extinct due to logging, ranching, and other destructive human activities. The Brown throated three-toed sloth and the Pale Throated three-toed sloth are believed to be relatively common and live in variety of Neotropical countries. However, the Maned three-toed sloth is currently on the United States Endangered Species Act and most of its previous habitat, the Atlantic Rainforest, has been destroyed (Emmons, 36-37). Today it is estimated that only five percent of the Atlantic Rainforest remains intact, making it extremely difficult to increase the number of Maned three-toed sloths. Other sloth species are protected under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), including the Brown Throated three-toed sloth and Hoffman’ s two-toed sloth (Emmons, 36-38). CITES will help to protect these species from being traded on the illegal wild animal market, but will not help to keep their habitats intact.
There are a variety of organizations dedicated to protecting the rainforests of Central and South America, which will help to protect habitats where sloths reside. There is one refuge that is dedicated solely to protecting sloths, the Aviarios del Caribe Sloth Refuge in Costa Rica (Baker). This 75 hectare refuge and rehabilitation center is committed to helping sloths and learning more about this creature that was named after one of the seven deadly sins. Babies are raised at the refuge and then are released back into the wild (Baker). This sloth sanctuary also provides educational programs for local schools and has an “adopt a sloth” program.

Works Cited

Baker, Christopher. Mammals. Online at http://photo.net/cr/moon/mammals.html. Viewed on 5/11/06.

Baker, Christopher. Moon Travel Planner. Avarios del Caribe Sloth Refuge. Online at http://www.moon.com/planner/costa_rica/mustsee/aviaros_caribe.html. Viewed on 5/12/06.

Emmons, Louise H. Neotropical Rainforest Mammals: A Field Guide. Chicago: The University of Chicago Press, 1990.

Goffart, M. Function and Form in the Sloth. Elkins Park: Franklin Book Company, INC., 1995.

Gould, Stephen Jay. “Can we truly know sloth and rapacity?” Natural History, April 2006, Vol. 105 Issue 4, p18-27.

Kricher, John. A Neotropical Companion. Princeton: Princeton University Press, 1997.

E.D. Montgomery, Gene. The Evolution and Ecology of Armadillos, Sloths, and Vermilinguas. Washington, D.C.: Smithsonian Institution, 1985.

Reebs, Stéphan. “Sit up when you Snooze”. Natural History, Oct2004, Vol. 113 Issue 8, p18-18

Species Profile. Online at http://www.rainforest-alliance.org. Viewed on 5/10/06.

The Three-toed sloth. Online at http://www.infocostarica.com/fauna/3sloth.html. Viewed on 5/10/06.



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