Order Sirenia, contains two families. The dugong has its own family and the three species of manatee have their own family. Order Sirenia only contains four known, living species. These species include the dugong, the Amazonian manatee, the West Indian manatee, and the West African manatee. There used to be fifth species called the Steller's sea cow, but it was hunted to extinction by explorers in the 1700s.

 

Sirenians are now classified as an endangered species. Sirenians are mammals so they have complex organ systems, way more advanced than a worm or a beetle. Sirenians reproduce sexually and give birth to live young and have a gestation period of 13 months, or 1 year and 1 month. Manatees only have one young per birth, and they usually wean their young anywhere from 1 to 3 years.

 

Sirenians have a lifespan of over 30 years and possibly up to 60 years. They have no specific breeding or calving season. Their young are usually born in the shelter of a backwater. Calves are born dark-colored and can swim and surface on its own within half a day of being born. The calf rides on its mother's back and begins to eat some vegetation by three months of age.

 

Sirenians may be active throughout the day or night. Within a 24-hour period, adults have been observed to feed for 6-8 hours in 1-2 hour intervals, resting for 6-10 hours of the remaining time. A manatee rests by hanging suspended just below the surface of the water or by lying prone on the bottom. In these positions it sleeps, eyes closed and body still. Most feeding occurs between the surface and a depth of 4 meters/ 13 feet. Manatees normally cruise at speeds of 3-7 km/ 1.8-4.2 mph, although when pressed they can move up to 25 km/ 15 mph. The large tail flipper is the main source of swimming power, providing the forward motion as well as serving as a rudder, which it uses to change direction.

 

The average time a manatee is submerged in about 260 seconds (4.3 minutes), although a dive lasting 980 seconds(16.3 minutes) was recorded. Sirenians are a nomadic species, meaning that they will move from place to place. Manatees "wander" over hundreds of kilometers in order to meet their dietary requirements. But Sirenians only eat sea grass and other aquatic vegetation.