The various species of Nurse Shark are typically inshore tropical and subtropical bottom-dwelling Sharks. Nurse Sharks are brownish colored, quite sedentary, and commonly spotted lying on the bottom near shallow coral reefs, on sea grass flats, and around mangrove islands. They have tough skin that is well-suited to lying and hunting among sharp corals. Nurse Sharks have a catfish-like head and mouth with two barbels on the upper jaw and rows of small teeth suited for grinding shelled invertebrates. They feed at night by grubbing through the bottom sediment hunting for small stingrays, molluscs, and crustaceans. Nurse Sharks are an important research species because they easily tolerate capture, handling, and tagging. Although they appear slow and harmless, Nurse Sharks rank fourth for documented human bites. This could be due to their near-shore lifestyles and slow, quiet nature that might tempt a diver to approach or even touch a Nurse Shark.