Biology of a Florida Manatee

The Florida manatee (Trichechus manatus latirostris) is a subspecies of the West Indian manatee. It is a large gray aquatic mammal with a horizontally flattened tail. The average weight is approximately 1,000 pounds (454 kg), but it can exceed 3,000 pounds (1,361 kg). The average length is 10 feet (3 meters) but manatees measuring approximately 13 feet (4 meters) have been reported. They are agile swimmers that can perform complex maneuvers. Manatees can swim very quickly in short bursts -- 15-20 mph (13-17 kph)  -- but they generally move much more slowly -- 3-5 mph (3-4 kph) -- as they cruise coastal waterways or forage on sea grasses and other aquatic vegetation.

Characteristics

  • Skin is a thick hide sparsely covered with hair
  • The head and face are wrinkled with vibrissae (whiskers) on the snout
  • The two forelimbs, or flippers, are paddle-shaped, with 3-4 nails at the tip, and are used to steer, hold food and guide movement along the bottom
  • There are no hind limbs
  • The lips help guide vegetation into the mouth
  • Communication is with touch, sight, taste and sound (high pitched clicks and chirps)
  • Manatees are "mildly social," but their social structure is loose, with animals merging to form transitory groups (with the exception of mom /calf relationships)
  • Manatees are not aggressive and they have no social hierarchy

For manatee anatomy details click here.

Habitat

  • Found in coastal areas -- rivers, estuaries and saltwater bays
  • Manatees have a low generation of body heat resulting in vulnerability to cold temperatures.  So when water temperatures drop below 68 degrees, they seek warmer waters around power plants and in natural springs (collectively called warm water refugia)

Eating

  • Manatees are one of the few marine mammals that are herbivores, meaning they eat mainly aquatic vegetation
  • They eat approximately 10% to 15% of their body weight each day
  • The upper lip is flexible to assist in the grasping of food

Breathing

  • Breathing is through the nose; special flaps close when diving
  • The lungs are located dorsally (making them vulnerable to boat strikes), extend the full length of the body, and assist in buoyancy
  • Manatees may stay submerged up to 20 minutes when resting
  • When using a great deal of energy, they may surface to breathe every 30 seconds

Reproduction

  • The reproductive rate is very slow; on average only one calf is born every two to three years
  • Sexual maturity for females is about 5 years and about 3 for males
  • After approximately a 13-month gestation period, the calf is born, weighing about 60 pounds and averaging 3 to 4 feet (1 meter) in length
  • The mother nurses the calf for approximately one year

Mortality

  • Manatees have no natural enemies and have been reported to live up to 60 years
  • The largest human-related, recognized threats to the manatee population are: loss of warm-water refuges, collisions with watercraft, being crushed or drowned in canal locks or flood gates and ingestion of fishhooks and monofilament line
  • Cold weather and red tides also kill and debilitate manatees, occasionally in very large numbers (> 150 animals dead/year)
  • Factors such as contaminants and disease almost certainly affect manatees, but to an unknown extent

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