Animal Diversity Web

Diversity

Bradypus (three-toed sloth) has four different remarkable species, B. tridactylus, B. torquatus, B. variegatus, and B. pygmaeus all belong to this genus. Each species has its own variation or color and patterns that help distinguish them from one another as well as other morphological differences that will be discussed. Populations of these species are dispersed across parts of Central and South America. They can be found at different altitudes which demonstrates the evolution of characteristics that are suitable for their environments. Their polygynandrous mating system displays how these sloths attract a mate in strategic ways and how a mother contributes to the growth and development of her young. They are primarily Folivores and are prey for a variety of other animals among the rainforest. The three-toed sloth is a fascinating animal that plays a large role in their ecosystems and has economic contributions to the human world as well. They are at risk for habitat loss and are victims of human interaction. Conservation efforts are in place to try to preserve these amazing creatures. (Bezerra, et al., 2008; Bosque, 2007; Gardner, 2022; Hayssen, 2005; Nereyda, et al., 2015; "Three-Toed Sloth", 2022; Voirin, 2015)

Geographic Range

Bradypus is natively distributed amongst the tropical rainforests in South and Central America. The three toed sloths commonly reside in the dense Amazon rainforest where their ideal habitat lies in the tree canopies. The different species within Bradypus vary in distribution in these regions. B. variegatus (brown throated three-toed sloth) can be found from Honduras to northern Argentina and B.torquatus (the maned sloth) inhabits the small Atlantic forest of southeastern Brazil. Other species are restricted to more specific regions, like the Bradypus pygmaeus which is home to the Isla Escudo de Veraguas, a small Caribbean island off the northwestern coast of Panamaspecies. Since Bradypus are canopy mammals, they have remained within their range of the tropical forests and have not been introduced elsewhere. (Gardner, 2022; "Sloth Species", 2022; "Three-Toed Sloth", 2022)

• Biogeographic Regions
• neotropical
  • native

Habitat

As stated before, three-toed sloths are canopy mammals. The species within Bradypus favor complex vegetation structures. These animals thrive in high trees that are closed and have dense canopies. It will later be discussed how Bradypus's anatomy is designed to their benefit amongst the trees since their primary source of food is foliage. However, they do travel to the ground about once every six days to urinate and defecate. Being on the ground leaves them vulnerable to susceptible to predation. Therefore, their primary habitat is high up in the trees of the dense rainforests. Through studies, it has been shown that some species may reside closer to cocoa plantations due to increased opportunities for food. (Gardner, 2022; Nereyda, et al., 2015)

• Habitat Regions
• tropical
• terrestrial

• Terrestrial Biomes
• rainforest

• Other Habitat Features
• agricultural

Systematic and Taxonomic History

The order Pilosa consists of two suborders, Folivora (sloths) and Vermilingua (anteaters). The families Megalonychidae and Bradypodidae are classified under the Folivora order. The Bradypodidae family which consists of the Genus Bradypus.The taxonomic studies of three toed sloths and their relation to anteaters indicates that Bradypodidae split from Myrmecophagidae roughly 37 million years ago (MYA). The extinct Mylodontidae (giant ground sloth) did not genetically group significantly enough with Bradypodidae or Megalonychidae, which indicates trichotomy best describes their relationships. Genus Bradypus consists of four species; B. pygmaeus, B. torquatus, B. tridactylus, and B. variegatus. Divergence times have been discovered for species B. tridactylus, B. variegatus, and B. torquatus. B. torquatus appeared to have branched off from B. tridactylus and B. variegatus around 7.7 MYA. (Barros, et al., 2003; Hayssen, 2005)

There has been a variety of misidentifications and phylogenetic inconsistencies in regard to these species. Throughout time, there had always seemed to be a struggle with the nomenclature of the three-toed sloths. Interestingly, these misidentifications are attributable to their similar morphological features, like the face and throat colors. Molecular phylogenetics had been used to help distinguish them apart. By using segments of mitochondrial cytochrome-b and 16S rRNA, phylogenetic trees constructed and used to correct these misidentifications and inconsistencies in Bradypus taxonomy. (de Moraes-Barros, et al., 2011)

• Synonyms

  • Three-toed sloth
  • Folivora
  • Maned Sloth
  • Pale-throated sloth
  • Brown-throated sloth
  • Bolivian three-toed sloth
  • paresseux tridactyla
  • preguica
  • ai-ai
  • ai de Bolivie
  • preguica marmota

• Synapomorphies

  • long forearms
  • long, sharp claws
  • shorter hind limbs
  • coloration on face and throat
  • dense, course fur

Physical Description

Three-toed sloths have a combination of brown, dark brown, grey and white on the throat, face, chest, and shoulders. B. variegatus have a lighter brown color all over the body with dark brown on the throat and on the sides of the face and forehead. They appear to have a white colored 'mask' above their eyes and nose. This species has neither a medulla nor pigment granules. B. torquatus has brown pigment on the body and head with no appearance of a distinguishable white mark on the face. They do have a few lighter pigments around the eyes and nose but it is minimal. On the back of the head and shoulders they have deep brown, almost black fur that appears longer than the rest of the hair on the body. B. tridactylus is the most recognizable of the four species due to its unique presence of spotting and pale colored face. The body is a deep brown with appearances of beige spotting. The face and throat are pale colored with darker pigment around the mouth. B. pygmaeus has more grey, white, and soft brown fur. Their ashy colored appearance includes lighter fur above the eyes that are similar to the appearance of eyebrows. The bridge of the nose and bottom of the face also has lighter colored fur. The three-toed sloths have a silky underfur that is protected by long, coarse guard hairs. They can be seen with Algae on their overhair to function as camouflage. The direction of the hair lies downwards on the body in order to shed rain. Hair of three-toed sloths part ventrally and meets dorsally. (Hayssen, 2005; Mendel, 1985; Wujek and Cocuzza, 1986)

Individuals that inhabit areas of high altitude forests are significantly larger than individuals from the lower altitudes. This implies altitudinal differentiation populations and species. Portions of the limbs are primarily muscular while the extremities are primarily bone. Sexual dimorphism is found in body length, mane size, mane form, and size and shape of external genitalia. Females are significantly larger than males and mane size is darker and larger in males. They have three toes with large claws on each foot. Fore claws are measured at 70-80 millimeters in length while hind claws are generally 50-55 millimeters. (Hayssen, 2005; Lara-Ruiz and Garcia Chiarello, 2005)

Teeth of Bradypus species are not pointed. They almost flat on the occlusal surface. These characteristics are not suitable to have piercing bites or defense against predators. (Hayssen, 2005)

• Other Physical Features
• endothermic
• bilateral symmetry
• polymorphic

• Sexual Dimorphism
• female larger
• sexes colored or patterned differently

Reproduction

The three-toed sloth exhibits a polygynandrous mating system. Female sloths mate with different males during different breeding seasons, which occurs at the beginning of the year. Roughly around January through March. Studies have shown that 70% of female three-toed sloths a switched mates across time. Females use two strategies that seem influence mate switching across breeding seasons. They have been studied selecting a male from a pool of males in their activity center and mating with different males by shifting their home ranges during estrus. These two methods support the polygynandrous mating system among Bradypus species. (Brattstrom, 1996; Hayssen, 2005)

• Mating System
• polygynandrous (promiscuous)

As previously stated, the breeding season for the genus Bradypus is around the beginning of the year, anywhere between January and March. The gestation period is typically four to six months. Neonate sloths are generally born around August or September. Females have an interbirth of about ten to twelve months. Interestingly, it was recorded that copulation was observed in Pernambuco, Brazil in the months July and November. A juvenile remained on its mother's abdomen during the November copulation. Male three-toed sloths seem to mostly initiate copulation. However, it is speculated that a female in oestrus can actively initiate mating as well. Copulation instances have been observed where the both and female raise their tails which may also be a mating signal. (Hayssen, 2005; Taure and Richard-Hansen, 1997)

• Key Reproductive Features
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
• viviparous

The female three-toed sloth, like most mammals, raise their young on their own. Males do not contribute at all to caring for neonate sloths. Juvenile sloths learn food preferences i by licking leaf fragments from their mother's lips and by eating what the mother eats. Social weaning occurs six months after birth. Females leave the their home range in where they had raised their young. The females eventually return to that area to give birth again. Consequently, young sloths partially inherit their home range from their mothers. (Hayssen, 2005)

• Parental Investment
• precocial
• female parental care
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• inherits maternal/paternal territory

Lifespan/Longevity

The lifespan of Bradypus varies when in captivity and when in nature. Historically, sloths in captivity were not exposed to quality maintenance and techniques necessary to keep them alive. They could kept alive in captivity for typically no longer than a month. However, throughout time accommodations have been made to meet their unique needs and they now can live from anywhere between twenty and thirty years in captivity. The Bradypus lifespan is relatively different in nature than those in captivity. The B.variegatus species begin to mature around three to five years of life and can live to be twelve to twenty years. Predation and disease can limit the lifespan in nature, where these factors are combatted in captivity where sloths are protected and can be medicated. (Brown, 2022)

Behavior

The species within Bradypus are both a solitary and social species. For most of their life, they are typically alone and don't encounter social interaction unless it's their offspring or when mating. It is common to associate slow movement with this genus, but they have been seen to move quickly. When being chased by a predator or trying to escape weather, the Bradypus sloths can move swiftly. They also are active during a various times in a 24 hour day. Bradypus sloths do not follow a circadian rhythm and have been seen to be active at night. Their geographical distribution can be explained for this. Elevation and temperature also factor into the Bradypus sloths' activity. They have been reported to concentrate their activity towards the warm daylight hours in low mean temperature forests where the elevation is between one 1,000 and 1,500 meters above sea level. However, in the Amazon at 35 meters above sea level, it was recorded that Bradypus sloths were feeding and locomoting at night because the forest canopy during the day is much warmer than highland forests and Atlantic coastal mountains. (Brattstrom, 1996; Castro-Sa, et al., 2021)

• Key Behaviors
• arboreal
• scansorial
• diurnal
• nocturnal
• motile
• sedentary
• solitary

Communication and Perception

Social interactions amongst Bradypus sloths are typically rare because of their solitary habits. However, sloths do use vocalization to communicate with offspring which is vital during infant dependance. When the offspring reaches independence and detaches from the mother's abdomen, they use contact calls to communicate. A mother's interaction with her offspring is vital for their development in feeding, self dense, and gaining confidence to move among the treetops. Stress calls of offspring can be differentiated by mothers based on the pitch, tonal qualities, and duration. The calls function over relatively long distances and can differ depending on how rich that part of the forest is with birds and bugs. Stress calls may form from different heights in the trees in order to combat the "background noise" that may mask the contact call. (Montgomery and Sunquist, 1974; Soares and Carneiro, 2002)

• Communication Channels
• acoustic
• chemical

• Perception Channels
• tactile
• acoustic
• ultrasound
• chemical

Food Habits

The Bradypus are tree-dwelling omnivores that rely on the thick tree canopies for their food. Three-toed sloth's diets consist of 99.4& leaves with 67.2% being young leaves. Studies of stomach contents and direct feeding observations display at least 51 different plant species that they consume. These animals tend to feed during the mid-day hours and rest at dusk and dawn. In Northern Venezuela, three-toed sloths use more of the upper strata of the canopy, while in warmer lowland sites they tend to use intermediate levels. They have evolved postures that maximize their surface area and allow more exposure of their body when it's sunny. When cloudy, foggy or rainy they minimize their surface area by huddling. They have very long forearms (made primarily of bone) and claws that extend to reach leaves, twigs, and buds. They have small yet sharp teeth that they use to bite buds off branches and twigs. The Bradypus have modifications of the hyoid region and palate that allow for feeding upside down. The animals use the muscle to bite points at the distal, middle, and mesial tooth in order to break up leaves and sticks. (Bosque, 2007; Hayssen, 2005)

• Primary Diet
• herbivore
  • folivore
  • lignivore
• omnivore

Predation

The three-toed sloth is apart of the diet of the Harpia harpyja (harpy eagle) and the Panthera onca (jaguars). Humans, domestic dogs, and feral dogs could also prey on them in their attempts to disperse. The Eira barbara (the Tayra), a large, muscular mustelid carnivore, has been reported to prey on three-toed sloths. These animals can attack in the trees and when the sloths travel to the forest floor to defecate in which they are more vulnerable. (Bezerra, et al., 2008; Hayssen, 2005)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • Harpy Eagle
  • Tayra
  • Jaguars

Ecosystem Roles

Three-toed sloths have an entire ecosystem of microorganisms that live among their fur. Although some are harmful parasites that used the sloths as hosts, there are some that are beneficial to them. Three-toed sloths have three known algae that reside on the surface of the fur. This provides them with camouflage that allows them to blend in with the trees and avoid predation. The algae also serves a nutritional supplement when a sloth has a poor diet. Coprophagous pyralid moths also live among the sloth's fur, providing nitrogen as a decomposing agent for dying algae on the sloth. There is evidence that states that the coevolution between Bradypus and algae may have played a role in algae diversification. When they travel along the ground to defecate, this fertilizes the forest floor which helps nourish the ecosystem. Since their primary diet is leaves, twigs, and buds, this helps the environment by reducing any plants that may be dead, diseased, or invasive. If any seeds are ingested during the consumption of plants, they will later be passed through their digestive system and spread to other areas of the rainforest which increases the vegetation in their habitats. They are prey to other species, providing food to predators in the same ecosystem. (Fountain, et al., 2017; Hayssen, 2005)

• Ecosystem Impact
• disperses seeds
• biodegradation

Economic Importance for Humans: Positive

Due to their popularity and lack of knowledge on them, the three-toed sloth attracts tourism and scientists. Rainforests require a dense variety of life in order to remain sustainable. These canopy-dwelling animals keep the forest healthy which also results in fewer zoonotic disease that may effect humans, environmental stability, increased infrastructure, and less traffic accidents. Bradypus contribute to the health of these rainforests by foraging among the trees and providing a habitat to vital microorganisms. Research has been done on the ecosystem that inhabits the three-toed sloths fur. Three-toed sloths are also used for meat and medicine. More specifically, B. variegatus is used by indigenous Bolivians for their cultural crafts. The substances produced by algae in their fur have many disease fighting agents that are being studied in order to work against a number of disease. Indigenous groups in these areas have customs and beliefs that heavily intertwine with the nature. Three-toed sloths contributing to the healthy rainforests also contributes to the enrichment of these cultures. (Hayssen, 2005; Reeder, 2016)

• Positive Impacts
• pet trade
• ecotourism
• source of medicine or drug
• research and education

Economic Importance for Humans: Negative

The three-toed sloth is typically not an aggressive animal. Their herbivore dietary behavior keeps them mostly away from humans in the high tree canopies. However, when human and sloth interaction does occur, they can attack. They have very long, sharp claws and can cause large lacerations. These animals will bite if they have the chance. If a human is bitten or scratched, the injury itself probably wouldn't be lethal. However, sloths carry a wide variety of microorganisms on the surface of their skin and fur that can cause disease and infection in humans. Mosquitos and other disease causing organisms can be transferred from sloth to human when there is interaction. These sloths also Phleboviruses (major arthropod-borne viruses) which can cause disease in humans and other animals. ("Are Sloths Dangerous to Humans?", 2022; Oliveira Filho, et al., 2019)

• Negative Impacts
• injures humans
  • bites or stings
  • causes disease in humans

Conservation Status

The biggest threat towards Bradypus is human interference. the Three-toed sloths are critically endangered due to habitat degradation and all of the factors that are associated with it. Timber harvesting, increased development and building, and collecting are all forms of human interference that are seriously threatening the livelihood of these animals. Not only is the loss of their habitat effecting them, but also their increased popularity. Because of their scarcity and rareness, zoos, exotic pet collectors, and the pet trade all have a high demand for having three-toed sloths in their possession. It has been studied that nearly all attempts to own a three-toed sloth in captivity results in death. The International Union for Conservation of Nature (IUCN) has listed the species among Bradypus as critically endangered. Its high-risk status is inferred, due to its extremely limited range and threat of habitat loss. The United States Fish and Wildlife Service (USFWS), did not recognize the IUCN’s species threat classifications. Although B. variegatus has been listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna, B. pygmaeus was not automatically listed when it was declared an individual species from B. variegatus. The USFWS was reviewing an emergency petition to add the pygmy sloth to the United States Endangered Species List. There is currently movement towards making Escudo de Veraguas a wildlife refuge or national park to prevent future development and progression in habitat loss. (Voirin, 2015)

• IUCN Red List [Link]

  Not Evaluated

Contributors

Gabrielle Wiseman (author), Colorado State University, Audrey Bowman (editor), Colorado State University.

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