The nurse shark, Ginglymostoma cirratum is a bottom dwelling shark common along shorelines. Though this species will bite humans if disturbed, it is not usually considered a threat to people. The nurse shark is believed to be vulnerable or threatened by extinction throughout some of its range, but the International Community for the Conservation of Nature (IUCN) suggests not enough population data exists to show the true safety status of the species.
At birth, the nurse shark is only 10-11 inches (27-30 cm) in length. Females grow to be somewhat larger than males, and reach maturity at about seven feet long. Specimens have been reliably reported of achieving lengths of nearly ten feet, although claims exist of much large animals. A full-grown nurse shark weighs approximately 200-330 lbs (90-150 kg.)
Adult females reproduce once every other year, and have a gestation time of six months. Nurse sharks are ovoviviparous, meaning that they bear live young. The average birth will consist of about 30 young sharks, but reports suggest that some sharks birth as many as 50. Like most sharks, the pups are independent at birth, and do not remain together or with their mother. The life span of a nurse shark is 25-35 years in captivity, but somewhat less clear in the wild.
The appearance of the shark is generally gray, though pups are born with spots that fade over time. Nurse sharks have a particularly long tale and are noted for being smooth to the touch. Their strong jaws are filled with thousands of small, jagged teeth, which help them to break the shells of their prey.
Nurse sharks live in reef systems along continental shelves, where the food source is plentiful. They are common along many coasts, including both sides of North and South America and the West Coast of Africa. They are nocturnal creatures, resting on the bottom of the ocean during daylight hours and hunting for food at night. Observations have shown that some sharks form resting piles of up to 40 individual animals, but other evidence suggests that the sharks are territorial, and will sometimes stake out and defend a familiar cave or resting spot.
The diet of nurse sharks are largely made up of crustaceans, fish and shrimp, though research suggests they will snack on whatever it comes across. It has unique hunting habits, with some observers noting that it will prop itself up on its fins as a false shelter to bottom-dwelling creatures. Once the unwary crab or other creature wanders under its mouth, the shark swoops down to swallow it.
Currently, the IUCN does not possess enough data to determine the level of threat posed to the nurse shark. Since they are coastal dwellers, they are likely to be threatened by human activity, including commercial fishing and pollution. Nurse sharks are prized for their skin, which makes a particularly tough leather. Though they are not fished for in any large scale way, sharkskin products remain a popular trade item.
As a bottom-dwelling predator, the nurse shark is vital to maintaining the balance of the ocean’s ecosystem. Sea urchins, one of the nurse shark’s main foods, have been shown to flourish and completely destroy reef and kelp systems without the presence of culling predators. As with most marine animals, preservation of these sharks leads to preservation of the environment as a whole.