Longevity & Causes of Death
- Manatees probably live a maximum of about 50 to 60 years.
Manatees probably live a maximum of about 50 to 60 years.
- A consequence of manatee tooth replacement is that scientists cannot use the teeth to age individual manatees, a procedure commonly used for many other species of marine mammals. Scientists instead use a method of aging manatees based on studying growth patterns that develop on ear bones.
- Although predation has not been documented, scientists believe sharks, alligators, or crocodiles may occasionally attack West Indian manatees.
- Crocodiles and sharks sometimes prey on West African manatees.
- Jaguars, caimans, and sharks prey on Amazonian manatees.
Causes of Death
- Natural causes.
- Human-related causes.
- Watercraft accidents.
Manatees become entangled in fishing and crab trap lines,
sometime resulting in serious wounds.
This manatee's flipper became entangled in a crab
trap and will require medical treatment.
- Flood gates and navigation locks.
- As manatees swim upstream, they may encounter flood gates and navigation locks. When flood gates are left partially open, manatees sometimes swim through them. They may become trapped in the water current from the upstream side and drown. The remote-controlled flood gates have also crushed manatees.
- Entrapment in flood control gates and navigation locks regularly kill manatees and is the second leading human factor for manatee deaths. A record 16 manatees died from these devices in 1994. From 1976 to 2000, 166 manatees were confirmed dead from flood gates and navigational locks in the state of Florida.
- To help the problem, engineers are installing pressure-sensitive mechanisms on flood gates known to cause the most manatee deaths. The cost of each sensor is about $50,000 (U. S. Fish and Wildlife Service, 1995).
- Poaching and vandalism.
- In spite of the fact that manatees are legally protected, poachers and vandals are also responsible for manatee deaths. In some areas manatees are hunted for food. Others are victims of harassment.
- Accidental entanglement and pollution.
- Florida manatees have been found with fishing lines or crab trap lines wrapped around them. These materials can wrap tightly around the manatee's flippers, causing serious infections, amputations, or death.
- In a survey of 439 manatee carcasses, 14.4% had debris in their stomach.
- Habitat destruction.
- Since the 1950s destruction of the natural habitats of many coastal animals is accelerating at an alarming rate. Much of the suitable manatee habitat in Florida (seagrass beds, salt marshes, and mangrove areas) has been destroyed.
- The human population in Florida increases by nearly 1,000 people daily.
- About 250,000 acres of forests are lost every year in Florida and roughly one-fourth of the state remains semi-natural.
- Death increases.
- All total, a record 415 manatees died in 1996. Even when the 150 manatees that died from the red tide outbreak were subtracted, it was still the worst year for manatee deaths ever recorded in Florida. The total mortality rate for Florida manatees has risen an average of 5.3% every year since 1976.