The nurse shark is a member of the family Rhincodontidae, along with zebra sharks and whale sharks. Scientists are unclear about how they came to be called nurse sharks, but it is believed that the term "nurse" was derived from the common name "nusse," which originally referred to cat sharks of the family Scyliorhinidae. The nurse shark was once thought to belong to this family and is still referred to as a cat shark in some regions.
Adult nurse sharks are typically light yellowish tan to dark gray/brown. They have a stout body with smoother skin than most other sharks. Two fleshy appendages, or barbells, extend from their upper lip. These are actually sensory organs that help them to locate food hidden in the sand.
Nurse sharks live in tropical and subtropical waters of the Atlantic and Pacific oceans at depths of 3 to 250 feet. These bottom-dwelling sharks prefer coral reefs, salt flats and channels between mangrove islands.
Nurse sharks are nocturnal predators. Their diet consists of bottom-dwelling fish, octopus, squid, clams, conches, crabs, lobster, shrimp, sea urchins and coral. They have small mouths, but strong suction power that allows them to vacuum up food at high speeds.
Nurse sharks are nocturnally active, and are mostly solitary as they search for food. During the day, however, they will congregate in groups of up to 40 individuals, often lying in a sluggish pile on the ocean floor, or hidden under ledges or crevices in the reef.
There are no species that regularly hunt nurse sharks. However, they are occasionally preyed upon by larger fish such as tiger sharks and lemon sharks.
Nurse sharks are not widely commercially fished, but because of their sluggish behavior they are an easy target for local fisheries. They are sometimes considered a nuisance animal, taking bait intended for other fish. Their livers are often used for the rich oil that maintains their buoyancy, They're are also used as crab bait.