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Florida Manatee

Trichechus manatus latirostris

Listing Status

  • Federal Status: Threatened
  • FL Status: Federally-designated Threatened
  • FNAI Ranks: G2/S2 (Imperiled)
  • IUCN Status: VU (Vulnerable)

Appearance:

The subspecies of the West Indian manatee (Trichechus manatus) that occurs in Florida is also known as the Florida manatee (Trichechus manatus latirostris).

Florida manatees are large, aquatic mammals that are native to Florida. Adult manatees are typically 9-10 feet long from snout to tail and weigh around 1,000 pounds; however, they may grow to over 13 feet long and weigh more than 3,500 pounds. Manatees have two fore limb flippers that they use for steering movements and to hold vegetation while eating. A large, round, flattened paddle-shaped tail is used for swimming. Algae often grows on the backs and tails of manatees, which makes their skin color appear green or brown. Barnacles (found mostly on coastal dwelling manatees) often leave round scars from attachment sites; movement from saltwater to freshwater habitats clears the animals of these saltwater hitchhikers.

The West Indian manatee is a large gray aquatic mammal that commonly reaches a body length of nine to ten feet (2.7-3 meters) and a weight of 1,000 pounds (453.6.6 kilograms); however, it can grow to more than 13 feet (four meters) and weight up to 3,500 pounds (1587.6 kilograms).  Manatees feature a wide rounded tail and two flipper-like fore limbs that have three to four nails.  Flippers are used to maneuver in the water and to grasp vegetation while feeding.  The nostrils are located above the snout and have valves that tightly close when the manatee is under water.  Their small eyes have a membrane that can cover the eyes for protection.  The ear openings are small and external lobes are lacking.  Manatees have a flexible lip pad that is used to move food into their mouth.  Manatees have back teeth (molars) for chewing but no frontal teeth.  Teeth are continuously lost and re-grown throughout the manatee’s life.  Molars form at the back of the jaw and slowly progress to the front of the jaw where they will fall out.  This is seen as an adaptation trait for feeding on vegetation with sand mixed in.  Manatees can hold their breath up to 20 minutes when resting, but when active they surface to breath every three to five minutes. 

Habitat:

The West Indian manatee's range is from the southern United States throughout the Caribbean Islands, Central America, and to northern South America.

The West Indian manatee can be found along coasts and inland waters of the southeastern United States, eastern Mexico, the Greater Antilles (Hispaniola, Cuba, Puerto Rico, Jamaica), and Central America down to as far as northern Brazil.

In the United States, the Florida manatee, a sub-species of the West Indian manatee, inhabits the state’s coastal waters, rivers and springs. Some Florida manatee are known to travel up the eastern coastline into Georgia, the Carolinas, and a few travel as far north as Massachusetts during warm months.

In the Gulf, Florida manatees can be found west through coastal Louisiana and are occasionally sighted as far west as Texas. Prior to winter’s coldest months, manatees migrate to warm water habitats in Florida. These warm-water sites include artesian springs and power plant discharge canals. Florida is at the northern end of the manatee’s winter range and these warm-water habitats play an important role in their survival during the winter months.

Behavior:

west indian manatee map

Manatees are aquatic herbivores (plant-eaters). Also known as "sea cows," these herbivores usually spend up to eight hours a day grazing on seagrasses and other aquatic plants.  

Manatees use their tail in an up and down motion to propel themselves forward. Strong swimmers, they are capable of reaching speeds of 15 miles per hour in short bursts. Manatees rest from 2 to 12 hours a day either suspended near the water's surface or lying on the bottom, usually for several hours at a time.  

Like other mammals, manatees breathe air. When active, manatees must surface every 3-5 minutes to breathe, but can hold their breath for as long as twenty minutes when resting. The manatee's snout is often the only part of its body that comes out of the water when it breathes. 

While most people tend to see many manatees gathered together at winter warm-water sites, during the rest of the year these animals are semi-social as they travel around the state’s waterways in search of food, mates or places to rest. Except for cow/calf pairs and small mating herds, manatees do not need to travel together although they do socialize when other manatees are encountered. 

Manatees reach sexual maturity in 3-5 years (females) and 5-7 years (males) and may live over 65 years in captivity. Gestation is approximately 13 months and usually one calf is born. The calf may stay with its mother (cow) for up to 2 years. Male manatees (bulls) are not part of the family unit. Bulls will leave a cow alone after her breeding period is over. Of the wild manatees that reach adulthood, only about half are expected to survive into their early 20s.

The diet of the manatee primarily consists of marine and freshwater vegetation (ex. Syringodium filaforme) (Bester, n.d.).  This species feeds between six and eight hours a day, eating up to ten percent of its body weight in vegetation. 

Manatees can breed and give birth throughout the year; however, birthing usually peaks in the spring.  During the breeding season, males gather and pursue a female to form a mating group and breed at different times (Bester, n.d.).  The gestation time for the manatee is 13 months.  Manatees have a low reproductive rate, only giving birth to an average of one calf every three to five years.  Females give birth to their first calf between the ages of four and seven years old (Marmontel 1995; O'Shea and Hartley 1995; Rathbun et al., 1995).  The calf will stay with the mother for up to two years. 

Threats

The main threats to manatees are boat collisions and the loss of warm water habitat.  Manatees feed in shallow waters making them susceptible to interactions with boats.  Boat related deaths can be caused by propeller cuts, impacts from the hull or lower unit of the motor, or a combination of the two.  Large ships can crush manatees on the bottom of waterways or between the vessel and the wharf.  Impact related and crushing injuries cause various lethal internal injuries.  Due to the inability to regulate their body temperature (thermoregulate) in cold water, cold stress is a serious threat to the manatee (Irvine 1983).  The loss of warm water refuges is seen as a serious long-term threat to the continued existence of the manatee (U.S. Fish & Wildlife Service 2001).  Habitat loss is also an issue as coastal development and pollution can destroy seagrass beds and freshwater aquatic vegetation, which is the main food source of manatees.  Manatees are also at risk of becoming entangled in monofilament line (fishing line) and crab trap lines which lead to injury, rescues, and death in extreme cases.  Periodically, manatees will get crushed in flood gates and canal locks, or trapped in culverts where they drown or starve.  Other threats include diseases, natural disasters, and red tide.  Red tide is a dramatic increase of the Karenia brevis algae, which can be a danger to many marine species. 

Conservation and Management

The West Indian manatee is protected as an Endangered species by the Federal Endangered Species Act and as a Federally-designated Endangered species by Florida’s Endangered and Threatened Species Rule.  It is also protected by the U.S. Marine Mammal Protection Act and the Florida Manatee Sanctuary Act (FMSA).  The FMSA allows the State to set restrictions on boat speed and access in important manatee habitats.  FWC enforces these boating restrictions along with Federal and local government partners.

State Management Plan
Federal Recovery Plan

Learn more about living with manatees.

References

Bester, C. (n.d.). West Indian manatee. Retrieved August 1, 2011,   from Icthyology

Irvine, A.B. 1983. Manatee metabolism and its influence on distribution in Florida. Biological Conservation 25:315-334.

Marmontel, M. 1995. Age and reproduction in female Florida manatees. Pp. 98-119 in T.J. O'Shea, B.B. Ackerman, and H.F. Percival, eds., Population Biology of the Florida Manatee (Trichechus manatus latirostris). National Biological Service, Information and Technology Report 1. 289 pp.

O'Shea, T.J., and W.C. Hartley. 1995. Reproduction and early age survival of manatees at Blue Spring, Upper St. Johns River, Florida. Pages 157-170 in T.J. O’Shea, B.B. Ackerman, and H.F. Percival, editors. Population biology of the Florida manatee. National Biological Service Information and Technology Report 1. Washington, D.C. 289pp.