Sloth, Hoffman's Two-toed


Choloepus hoffmanni


The pelage has two types of hairs, long guard hairs and short underfur. The hair is structurally unique among mammals. The hair varies in color from dark brown to pale yellow, though the algal symbionts can tinge the hair green. The limbs are relatively long and the forelimbs are slightly longer than the hind legs. The forefeet have two digits which are tightly bound with skin. The hind feet have three digits. All digits have long, hook like claws used for suspension from branches. Each has five teeth in the upper jaw quadrant and four in each lower jaw quadrant; the exact homologies of the teeth remain unclear. Two-toed sloths have six to eight cervical (neck) vertebrae. The stomach is complex in order to increase the efficiency of digesting vegetation. Average weight is 12.5 lbs. (5.7 kg). Head and body length ranges from 21” – 27.5” (540 to 700 mm).

Family

Megalonychidae

Order

Pilosa

Class

Mammalia

Range

Central and South America from Nicaragua south to Bolivia, and from Peru east to Brazil

Habitat

Mature and secondary rainforests and deciduous forests

Life Expectancy

Up to 37 years in captivity

Sexual Maturity

4 to 5 years

Diet

In the wild, they eat primarily leaves and occasionally fruits and flowers; in the Zoo they are fed a scientifically developed, commercially available leaf-eater diet and assorted fruits and vegetables.

Status

IUCN – Least Concern, CITES - Appendix III (Costa Rica)

Behaviors

Two-toed sloths spend most of their time in trees, though they may travel on the ground to move to a new tree, and are excellent swimmers. They are strictly nocturnal, moving slowly through the canopy after dark, munching on leaves. It had been thought that sloths were among the most somnolent animals, sleeping from 15 to 18 hours each day. Recently, however, Dr. Neil Rattenborg and his colleagues from the Max Planck Institute for Ornithology in Starnberg, Germany, published a study testing sloth sleep-patterns in the wild; this is the first study of its kind. The study indicated that sloths sleep just under 10 hours a day. Two-toed sloths hang from tree branches, suspended by their huge, hook-like claws, which are two to three inches long. Sloths sometimes are found hanging off trees after they die. Nearly everything a sloth does, including eating, sleeping, mating, and giving birth, is done while hanging from the branches in the trees. The only time that sloths are normally found right side up is when they go down to the ground to defecate, which they only do about once every 5 days. Sloths have many predators - jaguar, eagles, and large snakes. 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 home is also out of reach for many larger predators. Their long, coarse fur also protects them from sun and rain. Though two-toed sloths may occasionally eat fruits and flowers, nearly all of their diet is composed 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. Like the unrelated artiodactyls, sloths have a multi-chambered stomach filled with symbiotic bacteria to help them digest the cellulose in their fiber-rich diet. It may take a sloth up to a month to completely digest a meal, and up to two thirds of a sloth’s weight may be due to the leaves in its digestive system. Female sloths may live in groups, while male sloths are usually solitary. In the wild, there are about 11 times more female two-toed sloths than male two-toed sloths. Female two-toed sloths give birth to a single offspring after an 11.5 month gestation period. Neonates cling to the hair on the mother’s ventral surface. Young first hang upside down at 20 to 25 days after birth and begin to feed away from the mother 5 months after birth. The pup will nurse for at least 9 months, and may remain near its mother for more than 2 years. Two-toed sloths reach maturity at 4 to 5 years old. Over parts of its range, Hoffmann’s two-toed sloth overlaps the range of the brown-throated three-toed sloth. Where this overlap occurs, the two-toed sloth tends to be larger and less numerous than its relative, showing less activity and being more nocturnal than the three-toed sloth.

Adaptions

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 mammal of the same size. Another energy saving strategy is maintaining a lower body temperature. When active, their body temperatures range between 86°F to 93°F (30 to 34 °C), and this temperature is still lower when resting. Sloths have very poor eyesight and hearing, and rely almost entirely on their senses of touch and smell to find food. Their fur, unlike other mammals, flows from belly to top, not top to belly. This is so that when it rains, and they are hanging upside down, the rain slides off the fur easily. In moist conditions, the fur hosts two species of symbiotic cyanobacteria, which provide camouflage. Because of this algae, sloth fur is a small ecosystem of its own, hosting many species of non-parasitic insects.

Special Interests

Sloths are members of the order Xenarthra, a group of mammals that appeared approximately 60 million years ago. Also included in this order are anteaters and armadillos. Xenarthra is from the Greek, meaning “strange-jointed ones.” There are five subspecies recognized: Choloepus hoffmanni capitalis, J.A. Allen, 1913, Choloepus hoffmanni florenciae, J.A. Allen, 1913, Choloepus hoffmanni juruanus, Lönnberg, 1942, Choloepus hoffmanni pallescens, Lönnberg, 1928, and Choloepus hoffmanni hoffmanni, Peters, 1858. The name of this animal commemorates the German naturalist Karl Hoffmann (December 7, 1823 - May 11, 1859). In 1853 he traveled to Costa Rica with Alexander von Frantzius to collect natural history specimens. He served as a doctor in the Costa Rican army during the invasion of William Walker in 1856. He died of typhoid in Puntarenas. Hoffmann is commemorated in the names of a number of animals, including Hoffmann’s Two-toed Sloth, Hoffmann’s Woodpecker (Melanerpes hoffmanni) and the Sulphur-winged Parakeet (Pyrrhura hoffmanni).

Folklore

Conservation

Habitat destruction is probably causing a decrease in the wild Hoffmann’s two-toed sloth population, but there is little reliable data on the number of wild individuals. Sloths and people have little contact with one another in the wild.

Jacksonville Zoo History

It appears that the Jacksonville Zoo may have had some type of sloth in its collection for at least a short time during the late 1930s. Hoffmann’s two-toed sloth first appeared on our inventory in 2003, and has successfully delivered an offspring here.

Exhibit

Range of the Jaguar