Choloepus hoffmanni

Geographic Range

Choloepus hoffmanni (Hoffman’s two-toed sloth) is a native South American mammal whose distribution also reaches Central America. The distribution extends from southern Nicaragua to Brazil and Bolivia and is composed of two disjunct populations. The northern population extends from Central America to northern and western Colombia, western Ecuador, and westernmost Venezuela. The southern population spans the area east of the Andes in Ecuador, Peru, Bolivia, and western Brazil. The two species of Choloepus ( Choloepus hoffmanni and Choloepus didactylus ) overlap partially in the Andean regions and western Amazonia.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

Hoffman’s two-toed sloths inhabit lowland forests as well as higher altitude rain forests. Habitat is limited primarily to areas of continuous canopy. Habitat selection is correlated with social inheritance of the mother’s home range and tree preference. Plant composition and availability change seasonally and also play a role in habitat selection. In areas where Hoffman’s two-toed sloths coexist with three-toed sloths ( Bradypus species), it is less abundant. Southern two-toed sloths inhabit similar habitats to those of C. hoffmanni , but they seldom coexist and thus mostly occupy exclusive geographical ranges.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• rainforest rainforest

Physical Description

Hoffman’s two-toed sloths are one of two species in the genus Choloepus . Species in this genus are easily identified by the presence of two claws on the forelimb. The other extant genus of sloths, three-toed sloths Bradypus , have three claws on the forelimb. Hoffman’s two-toed sloths have head and body lengths ranging from 58 to 70 cm, mass varies from 4 to 8 kg.

Males and females are monomorphic. Hoffman’s two-toed sloths have rounded heads and flattened faces. The small snout is naked and protrudes from the flattened face. Ears are round and thickened, almost always covered with hair. The coloration of body hair in adults is a mosaic of tan, blonde, and light brown. Shading of the hair over the head and back is often darker than the rest of the body. A good way to distinguish C. hoffmanni from C. didactylus is that the former lacks dark shoulder and forearm markings. The hair of C. hoffmanni can grow up to 15 cm. Hair covering the abdominal region grows from the midline laterally so that the hair is parted. This serves as an efficient means to expel run-off water since sloths spend the majority of their time hanging upside down. Sloths have two coats, a softer inner coat and an outer coat that is longer and coarser in texture. During dry seasons the coat appears brown. In times of abundant rainfall, the outermost coat takes up a green hue due to the growth of algae. The fur coat also assists in insulating the sloth.

The forelimbs are slightly longer than the hind limbs. The manus and pes are highly modified in C. hoffmanni . Functional digits are reduced to numbers II and III in the manus and II, III, and IV in the pes. Digits of the manus are syndactylous. The distalmost phalanges are curved and possess claws that extend 8 to 10 cm. Soles of the manus and pes are bare and equipped with thick-skinned glabrous pads. The tail is absent or vestigial.

One of the most constant mammalian morphological characteristics is the presence of seven cervical vertebrae. Only three genera are known to be an exception to this constant, Choloepus , Bradypus , and Trichechus . The number can differ from individual to individual but it varies in Choloepus hoffmanni from 5 to 8 cervical vertebrae. Shortening of the neck (fewer than 7 cervical vertebrae) in conjunction with thick musculature around the neck region and a robust clavicle provide the rigidity that is needed to support the head while inverted.

There are five upper and four lower teeth in each quadrant for a total of 18 teeth. Choloepus hoffmanni lacks deciduous teeth and, instead, has ever-growing or hypseledont teeth. The teeth lack enamel, instead they possess a harder layer of dentin which surrounds an inner softer layer of dentin. Teeth erupt as simple conical structures and over time wear into caniniform and molariform teeth. This process is termed thegosis. The softer dentin center is worn away more quickly than the harder outer dentin layer during occlusion. This in turn forms a basin in the center of molariform teeth with a sharper outer layer. In adults, the anterior teeth are caniniform and are separated from the homodont, molariform cheek teeth by a diastema. These anterior maxillary caniniform teeth occlude with the posterior surfaces of the mandibular caniniforms. This occlusion forms unique triangular beveled caniniforms, characteristic of Choloepus hoffmanni . In the cheek teeth, each mandibular tooth occludes anterior to the corresponding maxillary tooth by an interval of half a tooth length. Other cranial osteological landmarks include an incomplete zygomatic arch, of which the jugal has two processes (lower and upper); inflated pterygoid region forming sinuses; open tympanic ring supporting the tympanic membrane; and a crescent-shaped glenoid fossa.

• Other Physical Features
• endothermic endothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

Males advertise their presence by distributing pungent smelling anal secretions onto branches. This is thought to serve as a way to designate a meeting place between females and males. The female may also advertise that she is ready to mate by exerting a high-pitched scream. In response, interested males will move towards the female. If two males arrive at the same time, confrontation can occur. Confrontation between males is an upside down event. They grasp a branch with their hind limbs and swing with one or both forelimbs at each other until one of them gives up. The male that remains will mate with the female numerous times and then leave her on her own. Reproduction in C. hoffmanni also occurs in a hanging position.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Breeding in Hoffman's two-toed sloths is seasonal. Pregnancy occurs during the rainy season and births at the beginning of the dry season. The gestation period is about 11.5 months and usually yields a single offspring. Newborns are about 25.4 cm long and weigh approximately 12 ounces. Offspring are born with claws, which are used to cling onto the mother soon after birth. The mother carries her young for 6 to 9 months, thereafter the offspring is independent. It has been reported that young are able to consume solid food as soon as 2 to 5 weeks. Nursing may stop as soon as the end of the first month. Sexual maturity in Choloepus hoffmanni is reached at about the age of 3 in females and 4 to 5 years in males. The inter-birth interval lasts at a minimum 15 months.

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

Males typically lack interest following birth of offspring and are not involved in their upbringing. Females are the sole source of parental care following birth until independence. Newborns are partially precocial, although do depend on the mother for a short time. The mother carries her young wherever she goes, providing milk in the first month and solid food thereafter. While young are carried around by their mothers, they learn where and what types of leaves are best to eat. As a result of this, familial selectivity of tree types has been reported. Independence is usually acheived by 6 to 9 months.

• Parental Investment
• precocial precocial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female
• inherits maternal/paternal territory

Lifespan/Longevity

Longevity in the wild is 12 years and in captivity 31 years. Mortality in the wild can be due to age, death by natural predation, hunting by humans for bushmeat, and loss of habitat due to deforestation.

Behavior

As arboreal mammals, Hoffman’s two-toed sloths eat, sleep, mate, and give birth suspended from tree limbs. Individuals of Choloepus hoffmanni are primarily solitary. The only instances when interactions between members have been observed are during mating or in typical mother-infant interaction. Groups inhabit a single tree at any one time. It is rare that C. hoffmanni individuals leave the general area of their birth during their lifetime.

Hoffman’s two-toed sloths are nocturnal herbivores. Activity usually begins about an hour after sunset and ceases by sunrise. During the day their location is mostly at mid-canopy and evening hours are marked by movement towards the upper canopy. They traverse tree tops in a hand-over-hand motion, traveling no more than 36.58 m in any one day. Length traveled by each step averages 30 cm. Locomotion characteristics of C. hoffmanni includes climbing, crawling, and hanging.

Body temperature fluctuates with the temperature of the environment. Hoffman’s two-toed sloths maintain a low body temperature of 24 to 33˚ C. They are unable to shiver to keep warm due to their low metabolic rate and decreased muscle mass. Although their fur offers some means of insulation, they further regulate their body temperature by moving in and out of the sun.

Although strictly arboreal, Hoffman’s two-toed sloths make their way to the base of trees once a week in order to defecate. This is usually done at habitual defecation sites. Other instances in which they travel to the ground are to change tree location and, on rare occasions, to give birth and mate. In order to make it to the ground, they descend head first. Once on the ground they use crawling locomotion. If forced to defend themselves, they use their sharp claws or sharp caniniform teeth. In periods of stress or to demonstrate aggressive behavior, Hoffman’s two-toed sloths may take on a pop-eyed appearance. They are capable of partially retracting the eyes when the eyelids are closed tightly, manifesting the pop-eyed appearance.

• Key Behaviors
• arboreal arboreal
• nocturnal nocturnal
• crepuscular crepuscular
• motile motile
• sedentary sedentary
• solitary solitary

Home Range

Home range sizes of Hoffman’s two-toed sloths range from 2 to 3 ha.

Communication and Perception

There is a limited information on communication and behavior. This lack of knowledge is largely due to their nocturnal, arboreal, and solitary lifestyle. Their sense of olfaction is well developed, evident by the use of scent marking by males. Males scent mark on tree branches via glands surrounding the anus. The purpose of scent marking is to establish a meeting place with the females so that mating can occur. The female may also vocalize via a high-pitched scream to advertise to males she is ready to mate. These sloths are generally silent but have been known to hiss in times of high stress or when agitated. Separation of an infant from its mother will elicit a loud low-pitched distress call ranging from 30 to 90 seconds. Tactile communication has been observed in the form of grooming between infant and mother. This is a mutual behavior and involves licking the head, face, and anogenital region.

• Communication Channels
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• scent marks scent marks

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Hoffman’s two-toed sloths are primarily folivores. Their diet consists of leaves, buds, tender twigs, young plant shoots, fruits, and flowers. They use their anterior caniform teeth to pierce, crop, and slice food and process it with the posterior molariform teeth. Daily food consumption in adults averages 0.35 kg. Digestion rate of leaves is the slowest of all herbivorous mammals, with a passing rate of about two and a half days. They have four-chambered stomachs, much like ruminants, which house bacteria capable of digesting the rich amount of cellulose present in their diets. Their slow metabolic rate allows them to survive on a small amount of nourishment as well as to neutralize plant toxins due to long gut passage times. Basal metabolic rate is about 45 kJ.

• Primary Diet
• herbivore herbivore
  • folivore folivore

• Plant Foods
• leaves
• wood, bark, or stems
• fruit
• flowers
• algae

Predation

As strictly arboreal mammals that move little and are cryptically colored, Hoffman’s two-toed sloths are relatively protected from predation. Their predators are are large, arboreal or avian predators, especially harpy eagles ( Harpia harpyja ). Other predators include jaguars, ocelots, other arboreal cats, and large snakes, such as anacondas.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Hoffman’s two-toed sloths host a variety of organisms, including gastrointestinal parasites, ectoparasites, and commensal arthropods (mosquitoes, sand flies, triatomine bugs, lice, ticks, and mites). Algae grows on the fur of C. hoffmanni , a mutual commensalism. The algae obtain a protected habitat growing inside the hair and the sloth becomes camouflaged alongside the foliage. The algae take up residence in the longitudinal grooves of the pelage. The algae, in addition to providing camouflage, may also contribute nutritional or trace element value to the sloths. Hoffman’s two-toed sloths also provide trees with fertilizer by defecating (accounting for 30% of their body weight) at the base of trees.

• Ecosystem Impact
• creates habitat
• keystone species keystone species

Economic Importance for Humans: Positive

Choloepus hoffmanni is considered a flagship species and plays a role in ecotourism.

• Positive Impacts
• ecotourism ecotourism

Economic Importance for Humans: Negative

There are no negative effects of Choloepus hoffmani on humans.

Conservation Status

According to the IUCN Red List, the status of Choloepus hoffmanni is of least concern due to their large distribution, large population sizes, and ability to inhabit somewhat disturbed areas.

Several factors that serve as potential population limiting factors of Choloepus hoffmanni include deforestation, agricultural activity, illegal trafficking, and an increase in human settlements. In addition, local communities bordering the habitats of Choloepus hoffmanni have been known to take these sloths up as pets. In efforts to combat the negative consequences due to human impingement several rescue and rehabilitation centers have been built to assist those animals that are injured. Although there are obvious negative consequences of habitat removal for animals as a whole, it has been hypothesized that C. hoffmanni might benefit from forest fragmentation which create edge habitats.

Other Comments

Choloepus is the only living genus of the family Megalonychidae. Fossil evidence shows that this family was once a much more diverse group and included many species of ground sloths. A Pleistocene megalonychid genus, Megalonyx , was widely distributed in North America and was notable for its very large size.

Unlike Bradypus species, Choloepus species easily adapt and breed in captivity.

Choloepus hoffmanni exhibits karyotypic variation, 2n = 49 to 54.

Additional Links

Encyclopedia of Life

Contributors

Vicky Apostolopoulos (author), Case Western Reserve University, Darin Croft (editor, instructor), Case Western Reserve University, Tanya Dewey (editor), Animal Diversity Web.

References

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