Although individuals of this species are largely solitary, mating herds form when a female is in estrus. These groups are made up of bulls pursuing the sexually receptive female. Courting bulls establish a dominance hierarchy for mating rights while the female attempts to avoid these males during most of her estrus cycle.
Females may attract up to 20 males, which pursue her for one week to one month.
Males reach full reproductive maturity between the ages of 9 and 10, but they are capable of mating as early as 2. Females are capable of reproduction at 4 to 5 years of age. Young females lack the skills necessary to raise calves and are less successful breeders. Most females breed successfully between the ages of 7 and 9. Gestation periods for West Indian manatees range from 12 to 14 months and calves are dependent on their mothers for about 2 years. One calf is produced at a time, however twins have been occasionally recorded. The inter-birth interval is 3 to 5 years, but this period may be shortened in the event of the early death of a calf. Calves nurse underwater from teats near the forelimbs. Calves are born with both molars and premolars and can begin consuming plants soon after birth, usually within the first 3 weeks.
The mother-young pair is the only stable, long-term association within the species. It has been suggested that the mother and her young can recognize each other after weaning and the association continues, to a certain extent, through the subadult years of the young. This long period of parental care might aid in the transfer of information about migration routes and other learned information.
(FPL 1989, Nowak 1999, Rathbun 1990)
Average birth mass: 32000 g.
Average gestation period: 335 days.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (male)
Sex: male: 913 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 1278 days.