Historically, manatees were hunted for the flesh, bones, and hide by Native Americans and later by the early colonists. Manatee fat was used for lamp oil, bones were used for medicinal purposes, and the hide for leather. This hunting is thought to be largely responsible for the manatee's initial decline. Natural events also imperil the lives of manatees. As the water temperature drops below 60 degrees Fahrenheit, manatees become sluggish and stop eating.
Young manatees are especially susceptible to the effects of cold temperatures.
Periodic red tide blooms have also been associated with a number of manatee deaths. Red tide toxins accumulate in sea squirts which adhere to sea grasses. This poison is ingested incidentally by manatees feeding on sea grasses. But the largest problems facing the manatee are caused by man. Speeding boats run over many manatees that are submerged just below the surface, killing them either by impact with the boat itself or by slicing into their backs with the propellers.