They sometime gather in small informal groups, but have no leader, or real structure. Breeding and Reproduction Manatees do not form permanent pair bonds. During breeding, a single female, or cow, will be followed by a group of a dozen or more males, or bulls, forming a mating group. They appear to breed at random during this time. Although breeding and birth may occur at any time during the year, there appears to be a slight spring calving peak.
Manatees usually bear one calf although twins have been recorded.
The gestation period is approximately thirteen months. Mothers nurse their young for a long period and a calf may remain dependent on its mother for up to two years. The cow assumes total responsibility for raising the calf without the bull. Calves nurse under water from a nipple located behind the cow's flipper and begin to eat plants a few weeks after birth. Scientists believe females do not become sexually mature until five to nine years of age.