Two types of sloths—two-toed and three-toed—live in Central and South America. They are the slowest mammals on earth, and this sometimes prevents female sloths from meeting their reproductive capacity of one offspring per year. Additionally, mothers care for only one offspring at a time, and do not mate again until it is independent. In two-toed sloths, for example, there is an interval of at least 15 months between births.
All sloths are solitary by nature, and come together only to mate. Two-toed male sloths use anal secretions on tree branches to advertise their presence while females in season emit high-pitched mating calls. Males move toward the screaming female, sometimes fighting each other if two manage to reach her at once. (Mating calls have not been observed in maned three-toed sloths, although they otherwise exhibit behavior similar those of to two-toed sloths.) Although sloths can breed year-round, most mating occurs toward the end of the rainy season and the very beginning of the dry season, when food is most plentiful.
Pregnancy and Birth
Two-toed female sloths typically give birth at the beginning of the dry season, after being pregnant for nearly a year. Three-toed sloths have a gestation period only half as long as that of two-toed sloths, with the maned three-toed sloth giving birth late in the rainy season. Pale-throated three-toed sloths mate later, and do not give birth until the beginning of the dry season. Sloth offspring are born with claws, which the baby uses to latch onto the mother’s belly, where it will nurse as the mother carries it for the first few weeks of its life.
Caring for offspring is the sole responsibility of the mother; males are not involved in the upbringing of their young and leave the female’s presence shortly after mating. Infant sloths are carried by their mother, first on her belly and then on her back, for the first six to nine months of their lives. Although infants may continue to nurse for up to four months, they begin eating vegetation within their second week. Mutual grooming between mother and young has been observed in two-toed sloths. Sloths also exhibit familial preferences for certain types of trees, since babies learn from their mothers what vegetation is good to eat.
Maturity and Independence
Young sloths are able to take care of themselves at around 6 months of age, but what happens at that point differs among the species. When the offspring of a pale-throated three-toed sloth reaches this point, the mother herself goes to a separate area, leaving the natal territory to her young. The young maned three-toed sloth leaves its mother’s home range for its own territory, after remaining with her for between 8 and 11 months. Two-toed sloths remain with their mothers until they are between 6 and 9 months old, but will spend their entire lives within the same general area where they were born.
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