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 mati ng 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 carr ied out during the filling of a hydroelectric dam, and captive data obtaine d from breeding records from different zoos. According to these data and a review of the literature, we determined the most likely values for differen t reproductive parameters in sloths. Choloepus didactylus have a 10-month g estation period with an inter-birth interval of 16 months or more; young be come independent around 12 months. The gestation period is similar in Cholo epus hoffmanni, but the inter-birth interval is 15 months and young become independent around 9 months. In Bradypus tridactylus pregnancy seems to las t 6 months, the inter-birth interval is approximately 12 months, and the ag e at which young become independent is about 5 months. In Bradypus variegat us the gestation period is 6 months and the inter-birth interval 10-12 mont hs; young become independent at 6 months. The occurrence of post-partum oes trus was established in both genera. All species of sloths have only one yo ung per litter; weaning takes place at a few weeks yet offspring continue r iding on their mother until independence. Reproduction does not appear seas onal in Choloepus didactylus, it may be slightly seasonal in Choloepus hoff manni; Bradypus variegatus have a mating season before the rains, and in Br adypus tridactylus reproduction is clearly seasonal. We suggest that these differences in reproductive strategies are basically linked to different di ets. Although sloths are not endangered at present, they are threatened by loss of rainforest habitat. Since these species have such a low reproductiv e rate and Bradypus do not adapt-let alone reproduce-outside their natural environment, it is essential to understand their habitat requirements and p opulation parameters for conservation purposes.