Manatees do not form permanent pair bonds like some animal species. During breeding, a single female, or cow, will be followed by a group of a dozen or more males or bulls, forming a mating herd. They appear to breed indiscriminately during this time; however, age experience of some males in the herd probably plays a role in breeding success. Although breeding and birth may occur at any time during the year, there appears to be a broad spring-summer calving peak.
The reproductive rate for manatees is low. The age of sexual maturity for females and males is about five years. On average, one calf is born every two to five years and twins are rare. Intervals between births range from two to five years. A two-year interval may occur when a cow loses a calf soon after birth. The gestation period is about a year.
Males assume no responsibility for raising the calf. Mothers nurse their young for one to two years, so a calf may remain dependent on its mother during that time. Calves nurse underwater from teats located behind the mother’s flippers and begin to eat plants a few weeks after birth. Newborn manatee calves are capable of swimming to the surface on their own and vocalize at or soon after birth.
Video from Save the Manatee Club’s webcams of Amber and her calf, when the calf was just six to seven weeks old. The “A’s” on Amber are freeze brands, which are used when a manatee is being tracked and has no other identifying markings. Amber was rescued as a calf, raised at SeaWorld for several years, and then released at Blue Spring State Park in Orange City, Florida. (Video ©Save the Manatee Club.)
Please remember to observe from a distance when you spot manatees in the wild and never disturb or separate a mother and calf. Manatee calves need their moms to survive!
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Female manatees usually seek quiet areas in which to give birth. In Florida, newborn calves can be seen at any time of the year, although more seem to be born in the spring and summer.
Most births are of a single calf about 120 centimeters (about 47 inches) long and weighing 30 kilograms (66 pounds), although a few cases of twins have been documented. The details of the birth process remain unclear but observations of calving in captive manatees have shown that the offspring can be born either head- or tail-first.
In the few cases in which births have been observed in captivity, the newborn calf is capable of swimming to the surface on its own, although the attentive behavior of the mother may give the impression that she is assisting the calf. Calves vocalize at or soon after birth and this is probably an important part of the mother-calf bonding process.
The calf begins to nurse within a few hours after birth, and nursing frequency and duration increases as the calf becomes more proficient. Calves nurse underwater from teats located behind the mother’s flippers and begin to eat plants a few weeks after birth.
The precocious calves are able to swim with their mothers within minutes of birth. A young animal commonly remains close to its mother’s side. Adult manatees typically swim in single file, but a calf always travels parallel to its mother, directly behind her flipper. It is possible that the animals can communicate most effectively in this position, or the formation is advantageous if the calf experiences less draft from the water.
Female manatees do not attack other manatees or humans that approach their young. Instead, they attempt to keep other manatees and human divers away from their calves by swimming between the intruder and their offspring. If the danger is perceived as severe, the female and calf will flee. A fleeing female – calf pair produces a duet, with one animal vocalizing and the other emitting an answering call.
A manatee calf may stay with its mother for one to two years, even though it is probably nutritionally independent by the end of its first year. The calf gets information on feeding and resting areas, travel routes and warm water refuges from its mother.
From Manatees and Dugongs © 1991 by John E. Reynolds III and Daniel K. Odell. Special thanks to the authors for granting permission to use this material.
When a female manatee goes into estrus, she is soon detected and pursued by numerous male manatees throughout the cycle (perhaps for a duration of up to three weeks). During that time, the female can mate with one or more males in what is known as an estrous or mating herd.
Many times, we will get phone calls at Save the Manatee Club notifying us that a group of manatees are “playing.” Sometimes people also call because they are concerned that the manatees in the estrous herd are injured, stranded, or in distress. In actuality, a mating herd is sort of a free-for-all. In shallower waters, the effect can be quite dramatic with churning waters and flailing flukes and flippers.
Manatee researchers are currently taking genetic samples of manatees (the animals are not harmed). Someday they hope to be able to establish paternity, which will help in determining the genetic health of the manatee population.