Maned three-toed sloth (Bradypus torquatus)
|Size||Tail length: 4.8 - 5 cm (2)|
Head/body length: 45 - 50 cm (2)
|Weight||3.6 - 4.2 kg (2)|
The maned three-toed sloth is classified as Vulnerable (VU) on the IUCN Red List (1).
The maned three-toed sloth is the rarest of the five sloth species and is only found in Brazil (3). The name refers to its black mane of hairs, each up to 15 centimeters long, running down the back of its neck and over the shoulders (2). Like other sloths it has long limbs, a short body and a stumpy tail (2). The head is round, with a flat face and small ears hidden in the fur. Its fur is coarse, long and shaggy, and grows in the opposite direction to most mammals; from the stomach to the back. The cream and tan coloured coat is usually tinged green from the blue-green algae that live in grooves in the hair, providing great camouflage for the sloth in the trees (3).
The reference in the name to three-toes is misleading; all species of sloth actually have three toes on the hind limbs, but they are grouped into two genera which can be distinguished by the number of fingers on the forearm. The two-fingered forms are known as two-toed sloths, and the three-fingered forms are called the three-toed sloths (3). These digits end in curved claws, measuring up to 4 inches long and are ideally shaped to hook around tree branches. Three-toed sloths also have an elongated neck due to an additional vertebra. This allows more flexible movement of the head and enables them to gaze at their surroundings in a 270 degree arc (3).
This species is restricted to the remaining fragments of coastal rainforest in Brazil, in the states of Bahia, Espirito Santo, Rio de Janeiro and Sergipe (1).
Inhabits tropical evergreen forests at low elevations, especially those with a continuous canopy (4).
The maned three-toed sloth spends practically its entire life in trees. It feeds strictly on leaves, twigs and buds and is well adapted to this way of life (5). It does not have incisors and crops leaves with its hard lips instead. The side teeth grow continuously as they are worn down by the grinding of food. Common to all sloths, the stomach is long and multi-chambered, and is filled with cellulose-digesting bacteria, which enables the extraction of energy from nutrition-poor leaves (6). It also has a low metabolic rate at 40-45% that of a typical animal their size, and it takes days to process food that other ruminants could process in hours. This benefits the sloth though, by enabling it to survive on relatively little food (3) (6).
As the sloth has such a low metabolic rate, it is an extremely slow and sluggish mover in the trees, travelling an average of 38 meters a day, and sleeping for around 15 hours of the day. It also maintains a low body temperature, from 30-34ºC, which helps conserve energy (3). This unusual animal has around half the body muscle of most other mammals, presumably to make more space for the digestive chamber, and so it cannot keep warm by shivering (3). Instead they select trees with exposed crowns and regulate their body temperature by moving in and out of the shade (4). Another unusual feature of this mammal is that it spends most of its time hanging upside down from branches and as a result, many of its internal organs are in different positions from other mammals (5). Sloths are also surprisingly good swimmers (4).
The maned three-toed sloth leads a solitary life and has a home range as large as 16 acres which can overlap with those of other individuals (3). It travels from tree to tree using canopy creepers, or more rarely by descending to the forest floor and crawling to the next tree (2). In the trees its motionless state and camouflage makes it difficult to see, but descending to the exposed forest floor renders the sloth vulnerable to predators such as jaguars and eagles, especially as it cannot escape by moving quickly and can only use its claws in defence (5). Due to these threats it only leaves its tree to find more food, to defecate around once a week and to find a mate (6).
Females give birth once a year to a single offspring after a gestation period of about six months. The young clings to the mother’s belly and is carried for up to six months, until it is strong enough to hang from branches unaided (4). There is a strong bond between the female and her young which is important for learning and development and the young inherit a portion of the mother’s home range. Even when the young leaves the mother’s home range, it maintains contact through calls (7).
The habitat of the maned three-toed sloth in the tropical coastal forests of Brazil is threatened by logging, charcoal production, urbanisation, industrialisation and clearance for plantations and cattle pasture (1). Today, the Atlantic Forest is reduced to less than 5% of its original extent and the area of the Mata Atlantica, where the maned three-toed sloth lives, has the highest human population in Brazil (8) (9). This sloth was previously hunted for its meat, and even though it is now protected by law, its numbers have been dramatically reduced and have not recovered (9). There have also been reports of this species being found in tourist areas where people pay to have their photograph taken with it, indicating that hunting is not totally under control (6).
Like so many species, the survival of the maned three-toed sloth is inextricably bound to the future of tropical rainforests. The Atlantic Forest, where this sloth is found, ranks among the top five global biodiversity hotspots, partly due to its high number of endemic species (10). There are several conservation measures being taken, which are hoped to protect the maned three-toed sloth. Currently the WWF is working with the local communities of the Atlantic Forest through environmental education programs to protect the habitat of this sloth and many other endangered species in the area (10). The US Agency for International Development (USAID) is working on reduced-impact forest management and on providing alternatives to slash and burn agroforestry (11).
Conservation International (CI) has plans to stimulate income through tourism, where agriculture might otherwise have been introduced; in 1998 a canopy walkway was built near the Una Reserve saving 320 acres of valuable rain forest habitat from logging, which is a hopeful message to other conservation projects (8). The maned three-toed sloth has a unique healing ability and is able to survive severe injuries (5). Scientists are also therefore keen to protect and breed this species so they can study the sloth's quick healing abilities and determine whether there could be benefits for human medicinal purposes (11). Efforts to relocate maned sloths in more secure areas of the rainforest have been successful so far, though breeding in captivity has been poor as sloths do not survive for long outside of their natural environment (11). Research projects are focusing on the close relationship between females and offspring so that breeding and re-introduction programs in the future are better informed and more successful (7) (12). These projects are hoped to allow the unique maned three-toed sloth to recover (8).
For more information on this species and other mammals of the neotropics see:
EDGE of Existence:
- Emmons, L. (1990) Neotropical Rainforest Mammals. University of Chicago, Chicago.
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- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Genera: a genus is a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
- Gestation: the state of being pregnant; the period from conception to birth.
- Ruminants: Animals that have a digestive process typified by the chewing of cud, which enables plant cellulose walls to be broken down in the stomach for energy. The vegetation is stored, regurgitated for more chewing, then broken down by specialised bacteria.
IUCN Red List (June, 2011)
- Emmons, L. (1990) Neotropical Rainforest Mammals. University of Chicago Press, Chicago.
- Macdonald, D. (2001) The New Encyclopedia of Mammals. Oxford University Press, Oxford.
- Eisenberg, J.F. (1989) Mammals of the Neotropics. University of Chicago Press, Chicago.
Animal Information (November, 2003)
Animal diversity (February, 2008)
- Soares, C.A. and Carneiro, R.S. (2001) Social behavior between mothers and young of Sloths. Brazilian Journal of Biology, 62(2): 249 - 252.
- Villa-Lobos, J. (1998) Tree Top Walkway in Brazil. Biological Conservation Newsletter, 176.
United Nations Environmental Programme: World Conservation Monitoring Centre (November, 2003)
World Wildlife Foundation (November, 2003)
US Agency for International Development (USAID) (November, 2003)
- Taude, E. (2001) Reproductive Biology and postnatal development in sloths. Mammal Review, 31: 173 - .