Choloepus didactylus (Linnaeus, 1758)

Russell A. Mittermeier & Don E. Wilson, 2018, Megalonychidae, Handbook of the Mammals of the World – Volume 8 Insectivores, Sloths and Colugos, Barcelona: Lynx Edicions, pp. 104-117 : 117

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Linnaeus’s Two-toed Sloth

Choloepus didactylus

French: Paresseux a deux doigts / German: Eigentliches Zweifingerfaultier / Spanish: Perezoso didactilo de Linneo

Other common names: Linné’s Two-toed Sloth, Southern Two-toed Sloth

Taxonomy. Bradypus didactylus Linnaeus, 1758 ,

“in Zeylona.” Corrected by O.

Thomas in 1911 to Suriname.

Subspecific taxonomy requires reassessment; different authors indicate potential differentiation between western and eastern populations. Monotypic.

Distribution. NE & S Venezuela (Orinoco Delta and S of the Orinoco River), the Guianas, N & NC Brazil (along the Amazon River W to Maranhao and S to Para and Mato Grosso states), and into upper Amazon Basin of SW Colombia (N up to Meta and Guainia departments), E Ecuador, and NE & E Peru;its S limit in W Amazonian Brazil is unclear. Additional visual records are described for SE Para State and need to be confirmed.

Descriptive notes. Head—body 540-880 mm, tail 9-33 mm, ear 20-38 mm, hindfoot 103-170 mm; weight 4-11 kg. There is no outward sexual dimorphism. Linnaeus’s Two-toed Sloth is the largest extant sloth species. It has long foreand hindlimbs, nearly equal in length. Forelegs have two large, curved claws, and hindlimbs have three. Teeth are rootless and ever-growing and lack enamel. Incisors are absent, and premolars are indistinguishable from molars. Pelage ranges from tan to buffy brown and, in the wild, can appear shaded pale green from algae that grows on hair. Face is light brown,is not furred, and has leathery texture. Throat hair is similar in color

to pectoral hair, and ventral hairis lighter than dorsal hair. Underfuris lacking, and abdominal hair is parted in middle and flows toward mid-dorsum. Young Linnaeus’s Two-toed Sloths tend to have soft and darker pelage. Diploid numbers range between 2n = 52-54 and 2n = 64-65.

Habitat. Primary and secondary tropical, moist lowland forests but up to elevations of 2400 m.

Food and Feeding. Linnaeus’s Two-toed Sloth is an arboreal herbivore and generalist. Its feeding behavior is poorly known, and most information comes from captivity. In captivity, they consume an average of 350 g/day of solid food. Coprophagy was observed in captivity. Linnaeus’s Two-toed Sloths were observed feeding at human latrines in north-eastern Peru, which could supply needed nutrients such as salt or protein from human feces.

Breeding. Linnaeus’s Two-toed Sloths reproduce year-round. Estruslasts 10-14 days, and ovarian cycles based on hormones are 4-5 weeks. Gestation lasts 330-350 days, and interbirth intervals are 14-27 months. Females give birth to single young and are not sexually mature before c¢.3 years old; males do not breed before 4-5 years old. Mating occurs abdomen to abdomen and takes place either on the ground or while hanging from a branch. Linnaeus’s Two-toed Sloths live up to 27 yearsin captivity, and one female gave birth at 25 years old. Mortality of infants in captivity is high. Females carry their infants on their ventral or dorsal regions; infants become independent at c.5 months old.

Activity patterns. Linnaeus’s Two-toed Sloths are nocturnal. They spend most of their time in forest canopiesto forage,rest, sleep, and breed. They descend to the ground to defecate every 3-5 days. In captivity, they spend 45% oftheir time sleeping, 25% foraging or grooming (mostly self-grooming), 20% resting with eyes closed, and 10% awake but inactive. When resting, they assume a sitting position hanging onto overhead support with one or more limbs or supported by hindlimbs while head and forelimbs are curled ventrally over groin.

Movements, Home range and Social organization. Linnaeus’s Two-toed Sloths are mostly solitary. They move between trees through interconnecting tree crowns or using lianas. Density in French Guiana is 0-5 ind/ha. In captivity, Linnaeus’s Two-toed Sloths seem to tolerate being kept in pairs or small groups; however, fighting between two males, probably for access to a female, was observed in captivity.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Overall population trends of Linnaeus’s Two-toed Sloths are still unknown, but they are unlikely to be declining fast enough to represent a conservation threat. Linnaeus’s Twotoed Sloths occur in many protected areas, but they are probably hunted opportunistically. Considering variation in karyotypes, a taxonomic review is needed to assure appropriate conservation action.

Bibliography. Adam (1999), Chiarello & Please (2014), Eisenberg & Redford (1999), Gardner & Naples (2008), Gilmore et al. (2000, 2001), Hautier et al. (2016), Heymann et al. (2011), Jones (1977), Moraes-Barros & Arteaga (2015), Rezende et al. (2013), Taube et al. (1999), Thomas (1911b), Trinca et al. (2006), Troll, Gottschalk, Heuer et al. (2015), Troll, Gottschalk, Seeburger et al. (2013), Voirin et al. (2013), Wetzel (1985a).

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Distribution. NE & S Venezuela (Orinoco Delta and S of the Orinoco River), the Guianas, N & NC Brazil (along the Amazon River W to Maranhao and S to Para and Mato Grosso states), and into upper Amazon Basin of SW Colombia (N up to Meta and Guainia departments), E Ecuador, and NE & E Peru;its S limit in W Amazonian Brazil is unclear. Additional visual records are described for SE Para State and need to be confirmed.