West Indian Manatee: Trichechus manatus

An Underwater Omnivore

The West Indian Manatee is a giant omnivorous aquatic mammal that is a distant relative to elephants and hyraxes. This particular species has at least two recognized subspecies, the Florida Manatee and the Antilles Manatee. A third subspecies in Northeastern Brazil may be universally recognized however as molecular data was collected from Garcia-Rodriguez et al. (1998). This page is based primarily on research from the Florida subspecies as this subspecies has had more research than any other subspecies or manatee species. While this species is technically referred to as the West Indian Manatee, this page often refers to the species as simply as the Manatee or when referring specifically about the Florida subspecies, as the Florida Manatee.

General Description:

The first thing people notice about the manatee when they first encounter one is its size. The West Indian Manatee (Manatee) can grow over 3,000 pounds and be over 13 feet long. In some ways, it is easy to see how it could be related to elephants. It has a similar color – manatees are grey or grey-brown and the skin is thick and wrinkled. One may also notice that manatees use their snouts to dig through the sediment. While muscles in elephants are very different, the similarity is evident. These snouts are thick and covered in stiff whiskers on the upper lip.

Behavior

All manatees are gentle, slow moving animals. Most of their time is spent resting, eating or in travel. They are usually quite shy and reclusive but may come up to humans. Often these are manatees that have had a history of being fed by humans. Manatees have evolved in areas where there are no natural predators and thus have no natural predator evasion behaviors. This makes them easy targets for hunting. A sad story of this is one of the West Indian Manatee’s relatives, the Steller’s Sea Cow which lived in the Berring Strait. It was descimated by hunting only 27 years after it was discovered by humans.

Sight: The depth perception of a Manatee isn't great. In fact it is quite limited. They have very small eyes. However, it has been shown that they can differentiate colors.

Hearing: Manatees can hear very well despite the absence of external ear-lobes.

Communication: Manatees emit sounds that are within human auditory range. They'll make sounds such as squeaks or squeals when frightened or communicating - particularly between cow and calf.

Breathing: A Manatee breaths through its nostrils which are on the upper surface of its snout. When a manatee submerges, their nostrils close tightly. Depending on the amount of activity, a manatee will breath every few minutes.

Habitat

Manatees can be found in shallow, slow moving rivers, estuaries, salt-water bays, canals and coastal areas, particularly where sea-grass beds flourish.

Range: The ‘Florida Manatee' is restricted to Florida in the winter months. In the summer, they can be found as far west as Louisiana and as far north as Virginia and the Carolinas.

The subspecies of West Indian Manatee known as Antilles Manatee is found in Central and South America as far south as Brazil.

Food

Manatees are completely herbivorous and eat aquatic plants. They can eat from 10 to 15% of their body mass in food each day.

Natural History

Manatees are believed to have evolved from wading plant-eating organisms. They are believed to share a common ancestor with the Elephant and Hyrax.

Abundance: There are approximately 1,200 left in the wild.

Reproduction

Female Manatees become reproductively mature when they are 5-9 years and males from 6-9 years old. Once pregnant, female manatees have a gestation period of 13 months. They can have one calf every 2-5 years. Twins are very rare in the wild. The young calf will stay with the mother nursing for 2 years. After that time they spend another year with the mother.

How long to Manatees live? Florida Manatees may live to be over 60 years old in the wild.

Conservation

Manatees were listed as endangered species under the U.S. Endangered Species Act of 1973. The USFWS recommended in 2007 that the Florida Manatee be reclassified as “threatened” instead of “endangered”. While the Florida Manatee has rebounded, there is controversy because this act takes significant protection off of the manatee. The IUCN however, has recently placed it in their Endangered List (October 2007) because of the low population size of the breeding population (under 2,500) and that the population is estimated to decline by 20% in the next 40 years. Current threats to Florida Manatees are almost all human-related activities. These threats include loss of habitat, boat propellers that hit the manatees, being crushed or drowned in flood gates, poaching and ingestion of lines and hooks. In addition to direct human threats, many manatees are also affected by natural disasters like hurricanes and red tides. However, the main threat to manatees is human related.

Related Species: West African Manatee, Dugong, Steller Sea Cow, Amazonian Manatee.

Resources

Garcia-Rodriguez, B. W. Bowen, D. Domning, A. A. Mignucci-Giannoni, M. Marmontel, R. A. Montoya-Ospina, B. Moreales-Vela, M. Rudin, R. K. Bonde, and P. M. McGuire (1998). "Phylogeography of the West Indian manatee (Trichechusmanatus): How many populations and how many taxa?". Molecular Ecology 7: 1137–1149. doi:10.1046/j.1365-294x.1998.00430.x.