How Nurse Sharks Work

Nurse Shark Prey and Predators
Waiting for dinner to swim by
Waiting for dinner to swim by
Wolcott Henry/Discovery Channel Images/Getty Images

Because the nurse shark doesn't do a whole lot of moving around, it might be hard to believe that they can catch any prey. And based on studies of nurse shark stomachs, they may not have to do much eating to maintain their low energy level. Frequently, when scientists examine the stomach contents of nurse sharks, they don't find anything; in three such experiments since the 1960s, food was found in less than half of the nurse sharks used in the test sample [source: Castro].

But when nurse sharks do eat, it appears they enjoy fish, mollusks such as octopus and squid, and crustaceans including lobsters and shrimp. Sometimes algae and corals have been found in nurse shark stomachs as well. This may have to do with their method of eating. With their muscular pharynx, the nurse shark sucks in food, sometimes hard enough to dismember it [source: Motta, Wilga]. Algae and coral might sneak in when the nurse shark sucks in its prey.

Putting up with algae and coral in their diet is another mark of how little effort the nurse shark puts into eating. Their hunting methods also seem to be ways to get food without expending much energy. For example, nurse sharks are mostly nocturnal creatures, which allows them to eat fish that are resting and would otherwise be too quick to catch. They also trap their own food. As we mentioned, the nurse shark can hover off the ocean floor with the support of its pectoral fin. Some nurse sharks have been observed hovering with their snouts pointed up, which they may do so that little fish and crabs swim under the nurse shark, seeking shelter. The nurse shark then descends and slurps up his dinner.

Although the nurse shark doesn't have any predators that routinely make a meal out of them, they have occasionally been found in the stomachs of lemon sharks and tiger sharks. Although they were once hunted for their liver oil, flesh and skin, they are rarely caught today, except by fishermen who see them as pests for taking the bait meant for other fish. While data are limited on the number of nurse sharks, they are not considered to be endangered or threatened.

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