Florida manatee (present in Kings Bay and Crystal River NWR year-round, but highest aggregation November – March = approx. 600 manatees vs. summer months = approx. 30 manatees).
The Florida manatee (Trichechus manatus latirostris) is a subspecies of the West Indian manatee (Trichechus manatus manatus). These aquatic mammals have elongated round bodies that taper to a flat, paddle-shaped tail. They have two forelimbs, called flippers, with three to four nails on each flipper. Their head and face are wrinkled with whiskers on the snout. The manatee’s closest relatives are the elephant and the hyrax (a small, gopher-sized mammal). Manatees are believed to have evolved from a wading, plant-eating animal known as the Pezosiren. The Florida manatee is related to the West Indian manatee, the West African manatee, the Amazonian manatee, the dugong, and Steller’s sea cow, which was hunted to extinction in 1768. The average adult manatee is about 10 feet long and weighs between 800 and 1,200 pounds.
Habitat and Range: Manatees can be found in shallow, slow-moving rivers, estuaries, saltwater bays, canals, and coastal areas — particularly where seagrass beds or freshwater vegetation flourish. Manatees are a migratory species. Within the United States, they are concentrated in Florida in the winter. In summer months, they can be found as far west as Texas and as far north as Massachusetts, but summer sightings in Alabama, Georgia and South Carolina are more common. Florida manatees have been known to migrate as far south as Cuba. The West Indian manatee is the species found in the coastal and inland waterways of Central America and along the northern coast of South America, although distribution in these areas may be discontinuous.
Behavior: Manatees are gentle and slow-moving animals. Most of their time is spent eating, resting, and traveling. Manatee are mostly herbivorous, however small fish and invertebrates can sometimes be ingested along with a manatee’s normal vegetation diet. They eat a large variety of submerged, emergent, and floating plants and can consume 10-15% of their body weight in vegetation daily. Because they are mammals, they must surface to breathe air. They may rest submerged at the bottom or just below the surface of the water, coming up to breathe on an average of every three to five minutes. When manatees are using a great deal of energy, they may surface to breathe as often as every 30 seconds. When resting, manatees have been known to stay submerged for up to 20 minutes. Manatees can swim up to 20 miles per hour in short bursts, but they usually only swim about three to five miles per hour.
Lifespan, Mortality, and Population: The Florida manatee has no natural enemies, and it is believed they can live 60 years or more. As with all wild animal populations, a certain percentage of manatee mortality is attributed to natural causes of death such as cold stress, gastrointestinal disease, pneumonia, and other diseases. A high number of additional fatalities are from human-related causes. Most human-related manatee fatalities occur from collisions with watercraft. Other causes of human-related manatee mortality include being crushed and/or drowned in canal locks and flood control structures; ingestion of fish hooks, litter, and monofilament line; and entanglement in crab trap lines. Ultimately, loss of habitat is the most serious threat facing manatees in the United States today. There is a minimum population count of approximately 5,000 animals according to recent aerial synoptic surveys.
Breeding and Reproduction: The reproductive rate for manatees is low. Manatees are not sexually mature until they are about five years old. The gestation period is 13 months. It is believed that one calf is born every two to five years, and twins are rare. Mothers nurse their young for one to two years, during which time a calf remains dependent on its mother.
Legal Protection: The Florida manatees in the United States are protected under federal law by the Marine Mammal Protection Act of 1972, and the Endangered Species Act of 1973, which make it illegal to harass, hunt, capture, or kill any marine mammal. Florida manatees are also protected by the Florida Manatee Sanctuary Act of 1978. Violations of these federal or state laws can be met with civil or criminal convictions associated with monetary fines and/or imprisonment.
Conservation: The Florida Manatee Recovery Plan was developed as a result of the Endangered Species Act. The recovery plan is coordinated by the U.S. Fish & Wildlife Service (USFWS) and sets forth a list of tasks geared toward recovering manatees from their current endangered status.
In October of 1989, Florida’s Governor and Cabinet directed the state’s wildlife agency to work with 13 “key” manatee counties in Florida to reduce injuries and deaths. These 13 counties were: Brevard, Broward, Citrus, Collier, Dade, Duval, Indian River, Lee, Martin, Palm Beach, St. Lucie, Sarasota, and Volusia. Over the years, these 13 county governments have worked with the state to develop site-specific boat speed zones to reduce the likelihood of watercraft collisions and to implement comprehensive manatee protection plans (MPP) for each county. Other conservation measures deemed important to saving manatees include: research addressing biology, mortality, population and distribution, behavior, and habitat of manatees; implementation of management plans; posting of regulatory speed signs and levying of fines for excess speeds in designated areas; manatee education and public awareness programs; and public acquisition of critical habitat and creation of sanctuaries.