Manatees are gentle and slow moving and may rest submerged at the bottom or just below the surface of the water coming up to breathe on average every three to five minutes. When using lots of energy they can come up for air as often as every thirty seconds and when resting can stay submerged for up to twenty minutes. They can be found in shallow slow moving estuaries, saltwater bays, canals and coastal areas. Manatees are a migratory species . Within the USA West Indian manatees are concentrated in Florida in the Winter but can be found in sun months as far west asTexas and as far north as Virginia. However sightings are rare. Summer sightings in Alabama, Georgia and South Carolina are common. They can also be found in some parts of South America. West Indian manatees have no natural enemies and are thought to be able to live up to sixty years. Many manatees deaths are human related. They are quite often killed by collisions with watercraft. Other causes of human manatee mortalities include being crushed and/or drowned in canals and flood control structures; ingestion of fish hooks, litter and fishing lines; getting tangled in crab lines and vandalism. Ultimately, however, loss of habitat is the most serious threat facing manatees today. There are approximately 3,00 West Indian manatees in the United States. Female manatees are not sexually mature until they are about five years of age and males mature when they're about nine years of age. Calves are born approximately every two to five years and twins are rare. Mothers nurse their young for one or two years and calves may remain dependant on their mothers during that time.