Behavior and Diet
Nurse sharks are nocturnal animals, spending the day in large inactive groups of up to 40 individuals. Hidden under submerged ledges or in crevices within the reef, the nurse sharks seem to prefer specific resting sites and will return to them each day after the night's hunting. By night, the sharks are largely solitary; they spend most of their time rifling through the bottom sediments in search of food. Their diet consists primarily of crustaceans, molluscs, tunicates, sea snakes, and other fish, particularly stingrays.
They are thought to take advantage of dormant fish which would otherwise be too fast for the sharks to catch; although their small mouths limit the size of prey items, the sharks have large throat cavities which are used as a sort of bellows valve. In this way nurse sharks are able to suck in their prey. Nurse sharks are also known to graze algae and coral.
Nurse sharks have been observed resting on the bottom with their bodies supported on their fins, possibly providing a false shelter for crustaceans which they then ambush and eat.
Nurse sharks are able to respire while stationary by pumping water through their mouths and out gills.
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