Mature females give birth to a single calf once every two to five years, but they do occasionally deliver twins. The mother shows concern over the calves' well-being during its initial breaths. Some scientists believe that the newborn animals require a learning experience to breathe properly, and it sometimes appears that a cow attempts to keep the baby near the surface. Also often seen is muzzling behavior between the cow and the calf that probably helps strengthen the baby's identification with it's mother. This behavior, also seen in many other animals, is called imprinting.

Two manatees together Manatee calves suckle milk from their mothers, and the cows' breasts are located just under the back edge of their flippers. When the calves are born, they weigh about seventy-five to ninety-five pounds, and are approximately two and a half feet long. They double their birth weight in just a couple of months.

When the calves are three to five months old, they begin to eat submerged vegetation such as hydrilla, ribbon grass, turtle grass, and manatee grass. At one year-of-age, they can weigh six to eight hundred pounds, and be over six feet long. Most calves will stay with their mothers for one to two years before venturing out on their own. To survive successfully, they must learn the locations of feeding areas, warm water refuges, and migratory routes from their mothers.

In four or five years, manatees are fully grown, and weigh about one thousand two hundred pounds, and are ten to twelve feet in length. Manatees can consume over 150 pounds of vegetation each day, and are not anatomically equipped (speed, teeth and the use of echolocation as with dolphins) for capturing fish.

Like elephants, they continue to grow throughout their lives -- the largest manatee ever recorded was 13 feet 4 inches long and weighed over thirty-two hundred pounds.

Very often, manatees cluster in small groups, which biologists call semi-social behavior. Typically, groups like these are formed for obtaining food, finding a mate, and avoiding predators. Whales, dolphins, seals, and sea otters are also known for similar behaviors. Every five or six minutes manatees have to come to the surface for a breath of fresh air, but this time interval varies according to their level of activity. Quite visible are the small flaps of skin in their nostrils that open to let in air and then close tight to keep out the water. During the manatees "resting state," their heartbeat slows down and they breathe only once every ten or fifteen minutes. Since much of this time is spent on the bottom, their vulnerability to boat strikes or other dangers is reduced during these periods. When they slowly float to the surface for fresh air, however, they may not wake up in time to get out of the way of speeding motorboats, the number one cause of manatee injuries and fatalities. This is the reason slow speed zones have been posted in many of Florida's coastal areas.



STUDY SUGGESTIONS: Manatees control their depth in water by controlling the amount of air in their lungs. The next time you go swimming, try floating with more or less air in your lungs and see what happens. Look up definitions for the words "herbivore," carnivore," and "omnivore." How do manatees and man compare?

Compare the social behavior of manatees with other animals, including man.

Write a short imaginative story about the social interactions of manatees.

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