Bradypus tridactylus, Linnaeus, 1758

Russell A. Mittermeier & Don E. Wilson, 2018, Bradypodidae, Handbook of the Mammals of the World – Volume 8 Insectivores, Sloths and Colugos, Barcelona: Lynx Edicions, pp. 118-132 : 131

3.

Pale-throated Three-toed Sloth

Bradypus tridactylus

French: Paresseux a trois doigts / German: \WeiRkehl-Faultier / Spanish: Perezoso tridactilo de garganta péalida

Other common names: Pale-throated Sloth

Taxonomy. Bradypus tridactylus Linnaeus, 1758 ,

“America meridionalis arboribus.” Restricted by O. Thomas in 1911 to Suriname.

This species is monotypic.

Distribution. N South America, from E Venezuela (E & S of the Orinoco River), E through the Guianas to N Brazil (W to the Amazon River Delta and bounded in the S by the Amazon River).

Descriptive notes. Head-body 450-755 mm, tail 22-110 mm, ear 5-21 mm, hindfoot 40-120 mm; weight 3.4-6.5 kg. Adult males are smaller than females. The Pale-throated Three-toed Sloth has long, coarse, dark gray hair with black spots, especially around back and shoulders. Pelage is greenish because of algae that grows along cracks of hair shafts. Throat and head are yellowish. Males have dorsal speculum with orange-yellow patch and broad black central stripe. Males and females have small vestigial tails. Females have two mammae on their chests. Chromosomal complement is 2n = 52 and FN = 56.

Habitat. Tropical forests with diverse tree species and complex horizontal and vertical cover. Although seldom seen, the Pale-throated Three-toed Sloth is abundant throughout its distribution.

Food and Feeding. The Pale-throated Three-toed Sloth is a strict folivore, consuming leaves from the canopy of overstory trees. Its diet has been reported to almost exclusively contain leaves of Cecropia spp. (Urticaceae) , butit also eats leaves of Ceiba samauma ( Malvaceae ), Elizabetha paraensis ( Fabaceae ), and Hevea viridis ( Euphorbiaceae ). The Pale-throated Three-toed Sloth has one of the slowest rates of digestion and fermentation because of the large volume of digesta it retains in its gut and its low metabolic rate.

Breeding. Breeding of the Pale-throated Three-toed Sloths is seasonal. Pregnancy, inferred from timing of births and assuming six-month gestation, occurs in August— February. One very small young is born per litter, and births appear to occur during the long rainy season (March—June). Interbirth interval is c.12 months, and age of independence for juveniles is ¢.5 months. Young cling to venters of their mothers. They sample leaves as early as three weeks old but do not consume substantial amounts of leaves until they are c.5 weeks old. Young are closely associated with their mothers for the first year oflife.

Activity patterns. Pale-throated Three-toed Sloths are strictly arboreal and do notlive outside of the forest. Similar to their congeners, they have limited activity; one individual was observed resting/inactive for 18-5 hours/day, hanging upside down from branches. While sleeping, they are most often seated in crooks of trees on horizontal branches, with their heads tucked into their chests under their arms. They have been observed sunning themselves in tree canopies. The Pale-throated Three-toed Sloth swims well and can use rivers as dispersal corridors.

Movements, Home range and Social organization. Pale-throated Three-toed Sloths are primarily solitary, although groups of up to three individuals have been observed. Individuals can be aggressive—primarily with their claws—to conspecifics if they occupy the same tree. They can reach high densities within Neotropical forests. In Suriname, it was the most abundant non-volant mammal and constituted a large proportion of total mammalian biomass in the forests.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Palethroated Three-toed Sloth has a relatively wide distribution, occurs in protected areas, and is rarely targeted for consumption or human use. Clearing of Neotropical forests is detrimental to Pale-throated Three-toed Sloths because they are vulnerable to habitat loss and fragmentation.

Bibliography. Beebe (1926), Eisenberg & Thorington (1973), Foley et al. (1995), Hayssen (2009b), Richard-Hansen & Taube (1997), Taube, Keravec et al. (2001), Taube, Vié et al. (1999), Thomas (1911b).

Figures

Plate 6 Species Accounts

Distribution. N South America, from E Venezuela (E & S of the Orinoco River), E through the Guianas to N Brazil (W to the Amazon River Delta and bounded in the S by the Amazon River).