Scientist have found that sharks can sense electrical currents. Every living thing gives out an electrical current or pulse. Sharks feel the electrical current through tiny holes, called pores, in the skin on their heads. The sharks use the information they receive to find fish to eat. They can even feel the very weak electrical current of a fish or ray buried in the sand on the ocean floor.
Nurse sharks do not normally attack people, but if you make them angry or afraid, they will bite you. They snap quickly when they attack and do not let go easily. Because nurse sharks sleep in shallow water during the day, it is quite easy to tread on them. That wakes them up with a fright and they give the nearest foot a quick nip. Nurse sharks rarely hurt anyone badly.
Female nurse sharks are unusual, because they can either lay eggs or bear live young. Nurse sharks’ eggs are 4 inches long when the young hatch from them. The mother shark does not look after her babies after they are born. She swims away and leaves them to find food for themselves.
The nurse sharks’ hinged jaws and sharp teeth make them dangerous both to humans and to other fish. Once their jaws are tightly shut it is difficult to get them to open their mouths again. Nurse sharks’ teeth are long and pointed. They look as sharp as needles. Nurse sharks look more fierce than they really are.
Nurse sharks eat squid, crabs, shrimp, fish, lobster and even spiny sea urchins. They have hinged jaws and huge mouths. Nurse sharks suck prey into their enormous mouths and swallow everything whole. The tawny nurse shark, which is sometimes called the giant sleeping shark, can spit as well as suck. It may spit at you if you frighten it.
Nurse sharks can be found off the east and southwest coasts of the United States and near the west coast of Africa. They live on the ocean floor, usually quite close to the shore. Nurse sharks are sometimes found in deep water where the ocean is very cold. Nurse sharks do not seem to migrate, but as the water cools they become even less active.
Nurse sharks are yellowish gray on their backs. Young nurse sharks may have darker spots on their backs. Their undersides are lighter in color. Nurse sharks do not look as sleek as some of the other sharks. Their bodies are more rounded. The average size for a nurse shark is about 7 feet, 6 inches. Females are only a little bigger than the males.
Nurse sharks are slow and clumsy creatures. They do not move around as much as some sharks and are often found just lying on the seabed. Sometimes as many as thirty nurse sharks may be seen sleeping on top of each other. Nurse sharks are nocturnal. This means that they sleep during the day and are active only at night.