A major threat is, of course, the most predacious mammal on the planet, man. The warm springs favored by manatees from time immemorial also provide an idyllic setting for single-family homes. However, this is not as bad as it sounds. Within the residential development and the harbor area of Crystal River, all boats are required to travel at idle speed. That gives the slow-swimming manatees time to dive when they detect a boat propeller headed their way.
Boats are the biggest danger to manatees.
In the open ocean, high speed craft hit them frequently. Researchers aren't sure how well the manatees hear boats or within what range. Recent studies suggest that they may be able to hear for only 160 feet. A powerboat covers that distance in no time. Tragically, about 85 percent of the manatees in existence in Florida have boat propeller scars on their hides.