The gestation period is approximately 13 months. Calves may be born at any time during the year. Usually only one calf is born, but twins do occur. They nurse underwater for about 3 minutes at a time from a nipple located behind their mother's forelimb. Born with teeth, calves begin eating plants within a few weeks but remain with their mother for up to 2 years.
Manatees communicate with each other by emitting sounds underwater that are audible to humans.
The vocalizations, which sound like squeaks and squeals, are especially important for maintaining contact between mother and calf. One field report described a mother and her calf, separated by a flood gate, calling to each other for 3 hours without interruption until they were reunited. Historically, manatees were hunted for the flesh, bones, and hide by Native Americans and later by the early colonists. Manatee fat was used for lamp oil, bones were used for medicinal purposes, and the hide for leather. This hunting is thought to be largely responsible for the manatee's initial decline.