Over the years, researchers have attempted to identify and quantify West Indian manatee distribution, population size and causes of mortality in order to understand manatees and the threats to their survival. They have isolated several causes of manatee deaths, most of which are directly related to human contact or encroachment. If these sources of mortality are not controlled, manatees may become extinct.
Scientists break down the causes of manatee deaths into six different categories:
- Watercraft Collisions: Manatee mortalities caused by the crushing impact of the hull and/or slashing of the propellers. In the case of large power vessels and barges moving through shallow waters, manatees may be caught between the vessel and the water bottom, or the vessel and a docking structure, and crushed. Watch our videos: In Danger on the Water and Manatees and Watercraft
- Flood Gate or Canal lock: Manatee mortalities caused when the animal is crushed and/or drowned in these structures.
- Other Human-Related: Manatee mortalities caused by monofilament line, fishing nets, fishing hooks, litter, poaching or other human activities. Watch our video: Manatees and Entanglement
- Perinatal: A dependent calf less than 150 cm (about 5 feet) that died around the time of birth and was not determined to have died from human-related causes.
- Other Natural: Mortalities caused by natural circumstances such as cold stress, red tide, gastrointestinal disease, pneumonia, and other diseases.
- Undetermined: The manatee is too badly decomposed to determine cause of death, the necropsy finding is inclusive, or the manatee carcass was reported and verified, but not recovered.