Bradypus variegatus
brown-throated three-toed sloth

Brown-throated three-toed sloths are native to South America and southern Central America. Their geographic range includes Bolivia, Brazil, Columbia, Ecuador, Honduras, Nicaragua, Panama, Paraguay, Peru, and Venezuela. Although once present in Argentina, it is now thought to be extinct. (Chiarello, 2008)

Brown-throated three-toed sloths can be found in many new-world tropical forests, though some have also been discovered in semi-deciduous forests and subtropical lowlands and swamps. They live in the canopy for the majority of their lives and are capable swimmers. They seldom travel on the ground. They can be found at elevations ranging from sea level to 2400 m. Although not selective about the species of tree they choose to inhabit, they tend to seek out trees with crowns that are highly exposed to sunlight. This preference has been attributed to the sloths using sunlight to fulfill their thermoregulatory needs. ("Brown-throated three-toed sloth (Bradypus variegatus)", 2008; Chiarello, 2008)

As indicated by their common, brown-throated three-toed sloths have brown coloration on their throat and head. Their coat consists of a layer of short, soft, and fine fur and a layer of thick, woolly fur. Algae often resides on outer layer, giving some individuals a greenish appearance. They have long forelimbs with three clawed-toes on each limb. They also have approximately 10 cervical vertebrate that enable them to rotate their necks up to 270 degrees. Their teeth are cylindrical and lack enamel. Similar to many ungulates, their stomachs are multi-compartmentalized, with intestinal microfauna that help digest cellulose from their exclusively vegetarian diets. Even as endotherms, brown-throated three-toed sloths have difficulty regulating their body temperature in cold environments and in cooler ambient temperatures. This is likely due to sparse muscle mass, their relatively small heart, and low-ranging heart rate. Adults range in mass from 3.49 to 5.19 kg, with an average of 4.34 kg. Average length is 60 cm, and they have a basal metabolic rate of 147 cm^3 oxygen/hour. Although size-dimorphism is not present in this species, males have a mid-dorsal speculum that is not present in females. (Feldhamer, et al., 2007; Gilmore, et al., 2001; Gilmore, et al., 2000)

Brown-throated three-toed sloths are thought to be monogamous. Females vocalize to attract males when they are ready to mate. Females typically mate with the first male they encounter. Although it is unclear if they have a defined breeding season, evidence suggests mating occurs just prior to the rainy season. Copulation lasts 10 to 15 minutes and takes place in the female's tree, approximately 15 m above the ground. During copulation, the male positions himself behind the female. Once mating is complete, the male leaves shortly there after. (Bezerra, et al., 2007)

Once copulation is finished, males immediately leave and do not provide any parental care to young. Bradypus variegatus gives birth to a single offspring once a year. During gestation, which lasts for 5 to 8 months, the mother does not make any preparations, such as nest-building. After birth, neonates are held ventrally, which is thought to help provide protection for young, including attack from predators. Neonates weigh less than 1 kg at birth. Most individuals become independent once weaning is complete, which takes approximately 4 months. Females become reproductively mature by 3 years of age, and males become reproductively mature between 3 and 5 years of age, with an average of 4 years of age. (Bezerra, et al., 2007; SOARES and CARNEIRO, 2002)

Brown-throated three-toed sloths give birth on the ground or in trees. During birth, the mother pulls the infant between her hindlegs, and other sloths aid in the birthing process by cleaning the mother and infant and by ensuring that the infant doesn't fall. Mothers help young establish motor behavior, posture, learning development, and independent exploration in young. Paternal care is thought to be non-existent in this species. (Gilmore, et al., 2000)

In the wild, the lifespan of adult brown-throated three-toed sloths is typically between 30 and 40 years. There is no other information available regarding the lifespan of this species. (MORAES-BARROS, et al., 2011; MORAES-BARROS, et al., 2011; MORAES-BARROS, et al., 2011)

Brown-throated three-toed sloths sleep approximately 14 to 16 hours a day and are both diurnal and nocturnal. They are active for approximately 8 to 10 hours a day, which is typically partitioned into discrete 2 to 3 hour periods. They are most active between 1200 and 1800 hours, and most individuals sleep between 0600 and 1200. Brown-throated three-toed sloths exhibit two different resting modes. The first is that of an "awake-alert" state during which the animal's eyes are actively open and blinking; the second is that of a "behavioral sleep", during which the animal's eyes are closed but still remains suspended from a tree. Adults have never been observed in the same tree with another adult. Agnostic behavior is relatively rare between conspecifics; however, they readily protect territory, food, or other resources. (Duarte, et al., 2003; Gilmore, et al., 2001; Greene, 1989)

The average home ranges of brown-throated three-toed sloths is less than 2 hectares. There is no further information on the home range of this species. (Gilmore, et al., 2001)

Social interactions between Bradypus variegatus adults are relatively rare. However, communication between mothers and their young is significant, particularly in the form of vocalization. Vocalizations are also used to communicate with other conspecifics during breeding season, as females call out to attract a potential mate. Bradypus variegatus lack a ciliary muscle in their eyes and have very few ganglion cells and nerve fibers, which result in poor eyesight and visual acuity. Evidence suggests that vision functions optimally at low light intensities. Defecation and urination occur on the ground, and both have been suggested to function as a means of communicating with other conspecifics. (Bezerra, et al., 2007; Gilmore, et al., 2000; SOARES and CARNEIRO, 2002)

Bradypus variegatus is a strict herbivore that feeds primarily on trees in the genus Cercropia (e.g., embauba). They consume various parts of the tree, including leaves, flowers, and fruits. Bradypus variegatus is a facultative drinker and receives most of its water from ingested plant materials. (Bezerra, et al., 2007; Duarte, et al., 2003; Gilmore, et al., 2000)

Brown-throated three-toed sloths are highly camouflaged and slow-moving, both of which help decrease risk of predation via decreased visibility. Major predators of this species include spectacled owls, harpy eagles and a variety of felid species. Brown-throated three-toed sloths descend from the canopy to defecate and urinate on the ground. Although they only descend from teh canopy once every 3 to 8 days, this behavior greatly increases vulnerability to predation. (Gilmore, et al., 2001; Touchton, et al., 2002; Voirin, et al., 2009)

Brown-throated three-toed sloths have are mutualists with algae, which reside in the coats of sloths. The presence of algae confers a greenish tint to the outermost fur coat, which is hypothesized to function as camouflage. It has also been suggested that algae provides essential trace elements and nutrients. In exchange, algae receives shelter in the coats of their host and sunlight, as sloths prefer sections of sun-exposed canopy. Brown-throated three-toed sloths are primary prey for a number of vertebrate predators including harpy eagles and many species of felid; however, they do not make up a large portion of any one species' diet. Known parasites of this species include Leishmania and Pneumocystis carinii. (Gilmore, et al., 2001)

There are no known positive effects of Bradypus variegatus on humans.

There are no known adverse effects of Bradypus variegatus on humans.

Bradypus variegatus is classified as a species of least concern on the IUCN's Red List of Threatened Species. Although precise population trends are unknown, is has been estimated that densities ranging from 2.2 to 8.5 animals per hectare occur throughout their geographic range. Although some populations in the Brazilian Amazon are thought to be declining due to deforestation, there are no major threats to the long-term persistence of this species. (Chiarello, 2008)