How to Identify a Nurse Shark

Video Transcript

"The marine organism we are going to identify now, is the nurse shark. The nurse shark is not your stereo typical tropical shark. They are bottom dwelling and feeding shark which can be commonly found resting on the bottom during the day in coral ravines, under coral ledges or in caves. They are gray to a purplish or yellowish brown in color. Nurse sharks have two relatively short dorsal fins and a tail with a long upper lobe and almost no lower lobe. They range in size from five to nine feet on average but have been reported to be found as long as fourteen feet. Nurse sharks are generally found at depths shallower than a hundred feet. They are found throughout the waters in the Caribbean and the tropical Atlantic ocean. Nurse sharks have a small mouth located underneath their head. Their snout is broad and rounded. They feed primarily at night by foraging through the sand for scrumptious morsels and food. Nurse sharks feed mainly on crustaceans, such as lobsters and crabs, small fishes, stingrays, octopi, squid, and mollusks such as skunk. They are able to eat these hard shelled animals because they have powerful jaws and unlike most sharks, they have parching plates instead pointy serrated teeth. Nurse sharks also have two barbels. One at either end of its mouth which it uses to dig through the sand for hints of food below. When they find something buried in the sand, they can use their strong gill muscles to pump water through their mouth to unearth the tasty morsels below. They will also occasionally use their broad snout to dig into the sand like a shovel. One unique characteristic of the nurse shark, that further sets it apart from most other sharks, is that it doesn't need to be constantly swimming to get enough water over its gills to breathe effectively. Instead, the nurse shark has a special muscle that allows him to open and close its gill covers manually while resting on the bottom to pump water over their gills. Nurse sharks can often be approached closely when they are resting on the bottom but any quick movement toward them or an attempt to reach out and touch them, will usually caused them to quickly swim away just above the surface of the reef. They post little threat to divers but I still wouldn't stick my hand too close to their mouth. I have heard stories of, although I have never witnessed it for myself, of divers been bitten by nurse sharks, usually when they are approached too closely or where divers pestering the shark. Nurse shark males can be easily distinguished from females by the presence of two claspers located on either side of the underside of their body near the anal fin. Nurse sharks mate in open water and the females carry the fetuses until they are born. Litter sizes can reach up to as many as two dozen baby sharks at a time. The baby nurse shark when newly born are usually about a foot long and resemble the adult shark. Gestation takes about six months and mating occurs just once every two years, usually between late June and the end of July. That's the nurse shark."