Reproductive biology and postnatal development in sloths, Bradypus and Choloepus: review with original data from the field (French Guiana) and from captivity

The reproductive biology of sloths remains obscure despite accounts on mating in the wild and in captivity. We present field data collected in French Guiana over a period of 16 months in the framework of an animal rescue carried out during the filling of a hydroelectric dam, and captive data obtained from breeding records from different zoos. According to these data and a review of the literature, we determined the most likely values for different reproductive parameters in sloths. Choloepus didactylus have a 10-month gestation period with an inter-birth interval of 16 months or more; young become independent around 12 months. The gestation period is similar in Choloepus hoffmanni, but the inter-birth interval is 15 months and young become independent around 9 months. In Bradypus tridactylus pregnancy seems to last 6 months, the inter-birth interval is approximately 12 months, and the age at which young become independent is about 5 months. In Bradypus variegatus the gestation period is 6 months and the inter-birth interval 10–12 months; young become independent at 6 months. The occurrence of post-partum oestrus was established in both genera. All species of sloths have only one young per litter; weaning takes place at a few weeks yet offspring continue riding on their mother until independence. Reproduction does not appear seasonal in Choloepus didactylus, it may be slightly seasonal in Choloepus hoffmanni;Bradypus variegatus have a mating season before the rains, and in Bradypus tridactylus reproduction is clearly seasonal. We suggest that these differences in reproductive strategies are basically linked to different diets. Although sloths are not endangered at present, they are threatened by loss of rainforest habitat. Since these species have such a low reproductive rate and Bradypus do not adapt—let alone reproduce—outside their natural environment, it is essential to understand their habitat requirements and population parameters for conservation purposes.