Play media Hoffmann's two-toed sloth climbing in a cage at Ueno Zoo (video)
Play media Hoffmann's two-toed sloth climbing in a cage at Ueno Zoo (video)
Hoffmann's two-toed sloth is a heavily built animal with shaggy fur and slow, deliberate movements. The fore feet have only two toes, each ending with long, curved claws, although three clawed toes are on each of the hind feet. Other features that distinguish it from three-toed sloths, which may be found in the same geographic areas, include the longer snout, separate rather than partially fused toes of the forefeet, the absence of hair on the soles of the feet, and larger overall size. The wrist of the sloth has developed some specific traits due to their slow, yet acrobatic motions. These evolved traits include diminution and distal migration of the pisiform bone, with a loss of contact with the ulna; reduction of the distal end of the ulna to a styloid process; and extremely reduced contact between the ulna and triquetral bone.
Hoffmann's two-toed sloth is, however, much easier to confuse with the related Linnaeus's two-toed sloth, which it closely resembles. The primary physical differences between the two species relate to subtle skeletal features; for example, Hoffmann's two-toed sloth has three foramina in the upper forward part of the interpterygoid space, rather than just two, and often – but not always – has fewer cervical vertebrae.
Adults range from 54 to 72 cm (21 to 28 in) in head-body length, and weigh from 2.1 to 9 kg (4.6 to 19.8 lb). Although they do have stubby tails, just 1.5 to 3 cm (0.59 to 1.18 in) long, this is too short to be visible through the long fur. The claws are 5 to 6.5 cm (2.0 to 2.6 in) long. Females are larger on average than males, although with considerable overlap in size. Their fur is tan to light brown in colour, being lighter on the face, but usually has a greenish tinge because of the presence of algae living in the hairs.
Hoffmann's two-toed sloth inhabits tropical forests from sea level to 3,300 m (10,800 ft) above sea level. It is found in the rainforest canopy in two separate regions of Central and South America, separated by the Andes. One population is found from eastern Honduras in the north to western Ecuador in the south, and the other in eastern Peru, western Brazil, and northern Bolivia. Based on cytochrome c oxidase subunit I sequences, a divergence date of about 7 million years between these populations has been suggested.
The five recognised subspecies of C. hoffmanni are:
Two-toed sloths spend most of their time in trees, though they may travel on the ground to move to a new tree. A study of sloths on Barro Colorado Island indicated that the Hoffmann's two-toed sloths there were almost exclusively nocturnal, even though in other locations they are known to be active during day. The authors attributed this in part to competition with the brown-throated sloth. They often move slowly through the canopy for about eight hours each night, and spend much of the day sleeping in tangles of lianas. They move only very slowly, typically at around 0.14 m/s (0.46 ft/s), although they can move up to 50% faster when excited. They are solitary in the wild, and, aside from mothers with young, it is unusual for two to be found in a tree at the same time.
The name "sloth" means "lazy", but the slow movements of this animal are actually an adaptation for surviving on a low-energy diet of leaves. These sloths have half the metabolic rate of a typical mammal of the same size. Sloths have very poor eyesight and hearing, and rely almost entirely on their senses of touch and smell to find food.
This species often exhibits exaggerated wobbling of the head. Another trait of this sloth is it often spits when the mouth opens. The saliva often accumulates on the lower lip, giving the creature a comical appearance.
Two-toed sloths hang from tree branches, suspended by their huge, hook-like claws. The clinging behaviour is a reflex action, and sloths are found still hanging from trees after they die. The sloth spends almost its entire life, including eating, sleeping, mating, and giving birth, hanging upside down from tree branches. Usually, sloths are found right side up when they descend to the ground to defecate, which they usually do about once every three to eight days. They will also ground themselves to urinate, change trees if they wish, or mate, as well as give birth. While terrestrial locomotion is usually thought to involve the sloth lying on the ground and pulling themselves forward, they have actually been seen walking on their palms and soles.
Sloths have many predators, including the jaguars, ocelots, harpy eagles, margays, and anacondas. If threatened, sloths can defend themselves by slashing out at a predator with their huge claws or biting with their sharp cheek teeth. However, a sloth's main defense is to avoid being attacked in the first place. The two-toed sloth can survive wounds that would be fatal to another mammal its size. The sloth's slow, deliberate movements and algae-covered fur make them difficult for predators to spot from a distance. Their treetop homes are also out of reach for many larger predators.
Their long, coarse fur also protects them from sun and rain. Their fur, unlike other mammals, flows from belly to top, not top to belly, allowing rainwater to slide off the fur while the animal is hanging upside down.
Hoffmann's two-toed sloth inhabits a range of different trees within its habitat, although it seems to prefer those with plentiful lianas and direct sunlight. They have a typical home range of about 2 to 4 ha (4.9 to 9.9 acres), and may spend most of their lives travelling between just 25 or so trees.
Courtship consists of the female licking the male's face and rubbing her genitals against the male's body. Gestation lasts between 355 and 377 days, and results in the birth of a single young. The birth takes place on either the ground or in the hanging position. Newborn sloths weigh 340 to 454 g (12.0 to 16.0 oz), and are precocial, already possessing long claws and able to cling to their mothers' undersides. They begin to take solid food at 15 to 27 days, and are fully weaned by 9 weeks. Although relatively quiet as adults, young sloths make loud bleating alarm calls if separated from their mothers.
In captivity, the two-toed sloth was seen giving birth by hanging upside down and attempting to pull the infant between her hind limbs and onto her abdomen. Other sloths were seen hanging under the mother and infant to protect the infant from falling.
Though two-toed sloths also eat fruits and flowers, most of their diets consist of tree leaves. They use their lips to tear off their food and chew with their peg-like teeth which have no enamel and are always growing. Although they are not true ruminants, sloths have three-chambered stomachs. The first two chambers hold symbiotic bacteria to help them digest the cellulose in their fibre-rich diets, while only the third chamber contains digestive glands typical of the stomachs of most other mammals. A sloth may take up to a month to completely digest a meal, and up to two-thirds of a sloth's weight may be the leaves in its digestive system.
Habitat destruction is probably causing a decrease in the wild Hoffmann's two-toed sloth population, but little reliable data is available on the number of wild individuals. Sloths and people have little contact with one another in the wild.
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 (Native )
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.
Range mass: 4 to 8 kg.
Range length: 58 to 70 cm.
Average basal metabolic rate: 45 cm3.O2/g/hr.
Other Physical Features: endothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes alike
Average basal metabolic rate: 3.891 W.
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.
Range elevation: 26 to 171 m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: rainforest
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.
Plant Foods: leaves; wood, bark, or stems; fruit; flowers; algae
Primary Diet: herbivore (Folivore )
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 ; parasite
Species Used as Host:
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
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 ; acoustic ; chemical
Other Communication Modes: scent marks
Perception Channels: visual ; tactile ; acoustic ; chemical
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.
Status: wild: 12 hours.
Status: captivity: 31 hours.
Status: captivity: 32.1 years.
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)
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.
Breeding interval: Interbirth
Breeding season: During the rainy season
Average number of offspring: 1.
Average gestation period: 11.5 months.
Average weaning age: 1 months.
Range time to independence: 6 to 9 months.
Average age at sexual or reproductive maturity (female): 3 years.
Range age at sexual or reproductive maturity (male): 4 to 5 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Average birth mass: 402 g.
Average gestation period: 350 days.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (female)
Sex: female: 730 days.
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 ; 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
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.
US Federal List: no special status
CITES: appendix iii
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
There are no negative effects of Choloepus hoffmani on humans.
Choloepus hoffmanni is considered a flagship species and plays a role in ecotourism.
Positive Impacts: ecotourism
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.