The West Indian manatee (Trichechus manatus), also known as the North American manatee, is a large, aquatic mammal native to warm coastal areas of the Caribbean, from the eastern US to northern Brazil. Living alone or in herds, it feeds on underwater plants and uses its whiskers to navigate. It is divided into two endangered subspecies, the Florida manatee (T. m. latirostris) in the US and the Antillean manatee (T. m. manatus) in the Caribbean, both of which face pressure from habitat loss, pollution, and other human activity. The West Indian manatee is the largest of the sirenians (order Sirenia), a group of large aquatic mammals that includes the dugong, other manatees, and the extinct Steller's sea cow. Manatees are herbivores, have developed vocal communication abilities, and are covered in highly sensitive whiskers (called vibrissae) that are used for feeding and navigation. In breeding season, several males form mating herds around an individual female; on average, one calf is born to a female manatee every two to three years. In the 1970s, the West Indian manatee was listed as endangered in the United States under the Endangered Species Act, when there were only several hundred left. The decades since have witnessed significant efforts to protect this species from natural and human threats, particularly collisions with watercraft. In 2017, the US changed the classification to threatened, citing a substantial increase in the total population. Description The average West Indian manatee is about long and weighs , with females generally larger than males. The largest individual on record weighed and measured long. Manatees are estimated to live 50 years or more in the wild, and one captive Florida manatee, Snooty, lived for 69 years (1948–2017). Since manatees are mammals, they breathe air, have warm blood, and produce milk. Like the other sirenians, the West Indian manatee has adapted fully to aquatic life, having no hind limbs. Instead of hind limbs, the manatee has a spatula-like paddle for propulsion in the water. Manatees have evolved streamlined bodies which lack external ear flaps, thus decreasing resistance in the aquatic environment. Pelage cover is sparsely distributed across the body, which may play a role in reducing the build-up of algae on their thick skin. Manatee skin is gray but can vary in coloration due to algae and other biota, like barnacles, that opportunistically live on manatees. Scar tissue on manatees is white and persists for