The West Indian manatee (Trichechus manatus) is believed to have evolved from a four-footed, plant-eating land mammal more than 60 million years ago. Its closest modern land relative is the elephant. The West Indian manatee belongs to the order Sirenia, which also includes the West African manatee, Amazonian manatee, the Pacific located dugong and the extinct Steller's sea cow. The Florida manatee (Trichechus manatus latirostris) is a sub species of the West Indian manatee.
Fossils of the present day manatee, as old as two-million years, and fossil ancestors of the dugong, as old as 45-million years, are found in Florida. These fossils are often found on dry land, in areas that were once shallow bays and estuaries, when sea levels were higher.
Legend has it that sailors who caught the first glimpse of the manatee mistook it for the Greek mythical "siren," a temptress who lured sailors to deadly reefs, rocks and treacherous waters. Christopher Columbus provided us with the first reference to the manatee in his logbooks from 1493.
Florida's waters host a variety of aquatic life. Perhaps one of the most mysterious is the Florida manatee. The Florida manatee is a large, plant-eating, warm-blooded marine mammal found in Florida's shallow coastal waters, rivers and springs. At first glance, the behavior of the manatee appears simple and unstructured, but the behavior is specifically adapted to Florida's sub- tropical climate.
The average adult manatee or "sea cow" is about 10 feet long and weighs approximately 1,200 pounds. It has a large, seal-like body that tapers to a large, spatula-shaped flat tail. The two forelimbs or flippers of the manatee are paddle-shaped with three nails at the tip of each flipper.
The finely wrinkled skin of the adult manatee is gray or gray-brown. The hair is thin and far apart, except for the stiff, brush-like facial whiskers, which help the manatee forage for food.
The manatee's eyes are small and are protected by inner membranes, which can be drawn across the eyeballs. Research indicates that the manatee can differentiate colors, but that its depth perception is limited. The manatee can hear well, even though its ears contain no external lobes. Its nostrils, located on the snout, are tightly closed by flaps of skin when the manatee is underwater and opened when it surfaces to breath.
Manatees spend approximately six to eight hours per day feeding. Their hearty appetites consist of 60 to 100 pounds of vegetation each day. The location of the manatee's mouth is well adapted for feeding on bottom vegetation. Manatees eat submerged and floating vegetation.
The manatee is generally a slow moving creature and is content to simply glide along, moving forward by using its tail and steering by using both its tail and flippers. Manatees use their flippers to help them swim and to hold vegetation while feeding. For its large size, the manatee is quite nimble, performing such underwater feats as upside-down swimming, head and tail stands and barrel rolls.
The manatee rests from two to 12 hours per day. It remains motionless with its eyes closed, either lying on the bottom or suspended near the surface. Air compression in the lungs allows the manatee to sink without exhaling or using its tail or flippers. While resting, the manatee may rise to the surface to breathe every seven to 20 minutes. When active, such as feeding or mating, they breathe every three to five minutes.
Manatees reach sexual maturity in approximately five years. Even though female manatees form very strong bonds with their calves, they do not form permanent associations with males after mating. After a gestation period of approximately 13 months, female manatees, called cows, bear one calf. Twins are a rare occurrence. During the first two years of its life, a calf remains very close to its mother's side for nourishment and protection. Cows give birth every two to three years, so it is quite possible to see a mother with a larger, older calf and a new, smaller calf at the same time.
At birth, calves are almost black in color, three feet long and weigh approximately 75 pounds. The calf nurses from its mother's nipples, located at the base of each flipper. During feeding, the mother can sometimes be seen rolling on her side or back to help the calf suckle. While calves are sometimes seen mouthing vegetation soon after birth, their long weaning period of up to two years allows time for the digestive tract to fully develop. This is important for animals who eat vegetation containing cellulose, so they may fully absorb nutrients.
Manatees are commonly found in coastal rivers, estuaries and canals. They move freely within salt, brackish and fresh water habitats, often in water less than six-feet deep. Manatees are a migratory species and Tampa Bay is home to more than 200 manatees during the winter and approximately 100 manatees during the summer.
