Enemies include otters, sheephead fish, sea stars, crabs, people. During low tide they recede into the shell and cover the opening with a hinged plate. Fertilized eggs hatch into larvae before leaving their parents' shells to swim freely until molting and settling down to sedentary adulthood. Enemies include snails, sea stars, sheephead fish, shorebirds and oil spills. Their camoulflage coloration helps protect them from predators.
Some sea hares discharge a purple inky secretion when irritated.
Sea hares are hermaphrodites and rarely live more than one year. The plates make the chiton flexible so that it can fit snuggly into a crevice or depression on the rocks. Some species have plates that are partially covered by a thick fleshy layer called a girdle or mantle. Under the plates the chiton has a broad oval foot for locomotion. Fossils of chitons have been found up to a half a million years old.