Manatees (Trichechus) are aquatic mammals that have a large, streamlined body, flipper-like front limbs, and a rounded, horizontal flipper-tail. Although they may resemble whales and dolphins in some ways, the are in fact more closely related to elephants.
There are three species of manatees:
- West Indian Manatee (Trichechus manatus)
- Amazon Manatee (Trichechus inunguis)
- West African Manatee (Trichechus senegalensis)
There are two subspecies of the West Indian Manatee: the Florida Manatee (Trichechus manatus latirostris) and the Antillean Manatee or Caribbean Manatee (Trichechus manatus manatus).
Manatees belong to the order Sirenia which includes the three species of manatee as well as one other species, the dugong. Manatees and dugongs are the only marine mammals that feed exclusively on plants and this characteristic impacts many aspects of their biology.
Since manatees and dugongs live their entire lives in the water and feed only on aquatic plants, they are restricted to coastlines, seas, and rivers where the water is clear and shallow enough for sunlight to penetrate and support plant growth.
A diet of aquatic plants places unique demands on manatees and their behavior and physiology reflects this. Since aquatic plants are low in nutrients, manatees must spend between 6 and 8 hours a day feeding. They consume up somewhere between 5 and 10 percent of their body weight each day (and a large adult animal can weight as much as 220lb). Manatees have a large upper lip that is lined with bristles and has two lobes that can be moved together to grasp onto food from the seabed.
As they chew, their teeth slowly migrate forward and new teeth at the back of the jaw replace old teeth that fall off at the front of the jaw. Like many animals that have a low nutrient diet, manatees have an extremely slow metabolism.