Sharing and enclosure in Twilight World with some Dourocouli monkeys are Bristol Zoo’s pair of Linne’s Two-Toed sloth, Choloepus didactylus. This is the commonest species of sloth to be seen in zoos, followed by its close relative Hoffman’s Two-toed Sloth C.hoffmanni.
Both species have multiple subspecies, and few if any in captivity are diagnosed as to which they belong to. For this reason the sloth’s in captivity are primarily display and research subjects, rather than captive breeding and reintroduction candidates. In any case, both species are widespread and are listed as of Least Concern by the IUCN.
With the distant evolutionary relationship between the living species, it becomes harder to generalise about them. It has been suggested that the symbiotic algae in sloth hair do more than provide camouflage, and the failure to maintain Bradypus sloths outside their native range is partly due to the loss of their symbiotes. It may also be that their need for behavioural thermoregulation means that an incorrect enclosure design makes it impossible for them to regulate their body temperature in a natural manner, with inevitable results.
Sloths have very slow metabolisms, and consequently have trouble maintaining a constant body temperature. Bradypus sloth’s habitually climb into open canopy in order to thermoregulate, especially in the early morning. This makes them vulnerable to Harpy Eagles, and sloth’s comprise at least a third of the diet of the eagle.
Choloepus appears to be strictly nocturnal in the wild, whereas many if not all species of Bradypus are active both day and night. Choloepus appear to feed on a wider variety of foliage, which makes them far easier to maintain. Bradypus feeds largely, though not exclusively, on Cecropia leaves, and is very reluctant to switch to new diets in captivity
In captivity Choloepus species will feed on almost anything (including animal protein) and are fairly regularly bred. Needless to say, this does not happen quickly – at Bristol we have had various births over the years but no successful rearing as yet. One birth occurred over a year after the male in the enclosure died, so pregnancy in Choloepus is at least 12 months and probably more. Once born, a baby will spend at least 6 months riding around on its mother’s belly before becoming independent.
.The chief conservation activity for sloths is habitat protection. As they are dependent on evergreen forest for the most part, and are very vulnerable to hunters, protection of the forest from fires or poaching is the best way forward to protect these ancient animals.
Next week, our other edentates, the yellow armadillo.
(images from wikipedia)