West Indian manatees in Crystal River National Wildlife Refuge, Florida, USA

© Norbert Probst/Getty Image

Life in the slow lane

Welcome to the clear, spring waters of the Crystal River National Wildlife Refuge in the US state of Florida. Usually solitary animals, these manatees can be curious and will approach boats. That's why Florida enforces special water speed zones, particularly when manatees are on the move to warmer areas for the winter. Loss of habitat and boat collisions mean that, although they have no known natural predators, manatees are still a vulnerable species.

These two have arrived in a natural freshwater spring in Crystal River, on the west coast of the Florida Peninsula. The refuge protects habitat for the hundreds of manatees that migrate here each winter. Most West Indian manatees off the coast of Florida live in shallow and marshy areas where they feed on sea grass, mangrove leaves and algae. The ocean's largest herbivore, these ‘sea cows’ nosh on greenery for almost half the day.

And what could be better than a nap after all that munching? Manatees will often sleep underwater for the other half of the day, coming to the surface for air in 15 to 20-minute intervals and grazing for food again in shallow waters.