Carcharias taurus

Grey nurse sharks, also called sand tiger sharks, can be found in the Atlantic, Indian, and Pacific Oceans in temperate and tropical waters. They are found in warm seas, except for the eastern Pacific. They occur from the Gulf of Maine to Argentina in the western Atlantic, the coast of Europe to north Africa in the eastern Atlantic, in the Mediterranean sea, from Australia to Japan in the west Pacific, and off the coasts of South Africa. ()

Grey nurse sharks are found in temperate and tropical waters. They are typically found in shallow waters, such as shallow bays, surf zones, and near coral or rocky reefs. They have been sighted in waters as deep as 191 meters, but will most likely be seen in the surf zone to a depth of 60 meters. They are usually found near the bottom of the water column. ()

The dorsal side of grey nurse sharks is grey, the underside is a dirty white color. These are stout-bodied sharks with metallic brown or reddish colored spots on the sides. When a grey nurse shark pup is born it is typically between 115 and 150 cm. As they mature, grey nurse sharks can reach 5.5 meters, but an average size is 3.6 meters. Females are generally larger than males. Average weight is from 95 to 110 kg. A distinguishing characteristic of grey nurse sharks is that the anal fin and both dorsal fins are the same size. The tail is heterocercal, with a long, upper lobe and a shorter, lower lobe. These different lobes allow for great movement. The mouth bears razor like teeth and is long and slender, with pointed snout. Their elongated teeth are visible even when the mouth is closed, giving these sharks a menacing appearance. This has led many to believe that these are dangerous sharks, a reputation they don't deserve. ()

It takes a grey nurse shark pup between 6-9 months to develop in the uterus of a female. Young nurse sharks develop a jaw and teeth very early their development and some eat their siblings while still developing within their mother, a phenomenon known as intra-uterine cannibalism. It is uncertain how long it takes grey nurse sharks to reach maturity, but maturity is estimated at between 5 and 13 years. Sharks continue to grow throughout their lives. ()

Little is known about the lifespan of ocean dwelling grey nurse sharks, however those held in captivity live to an average age of thirteen to sixteen years. It is believed that those in the wild live longer still. ()

Grey nurse sharks may travel in groups of twenty or fewer but most often occur alone. Group travel may improve mating success, feeding, and survival. Grey nurse shark are most active at night. During the day they stay near caves, cliffs, and drop-offs. Metabolic rates during the day (~200cm3/O2/hr) are much lower than at night (~325cm3/O2/hr). These are not aggressive sharks, but divers are warned not to intrude into their caves, or bother them. Grey nurse sharks gulp air and hold it in their stomachs to maintain neutral buoyancy. Because their bodies are dense, they tend to fall to the bottom, by retaining air in their stomachs, they are able to remain motionless in the water column. ()

Grey nurse shark populations in the northern and southern extremes of their range may make seasonal migrations to warm waters (towards the poles in summer and towards the equator in winter). ()

Home Range

There is no information on home ranges in these sharks.

Communication among grey nurse sharks is not well understood. Sharks in general are sensitive to electrical and chemical cues. ()

Grey nurse sharks, and other species of sharks, have pores on their ventral surface. These pores are instrumental in detecting electrical fields, which help them to detect and locate prey and may help in navigating using the earth's magnetic field.

Grey nurse sharks have a range of prey, including bony fish, rays, lobsters, crabs, squid, and other small sharks. Grey nurse sharks sometimes hunt cooperatively, chasing fish into small groups and then attacking them. Grey nurse sharks, like other sharks, have been known to attack at random during feeding frenzies, where a large number of prey is found together. In feeding frenzies sharks rely heavily on their electroreceptors, attacking everything in close vicinity. ()

The only know predators of adult grey nurse sharks are humans. Human hunting has caused population declines, both as a result of shark fishing and persecution because their fierce appearance has caused them to be mistaken for other, more dangerous, species of sharks. They are also accidentally caught in commercial fishing nets. Young sharks are eaten by other sharks. ()

Grey nurse sharks help to regulate prey populations. Different species of lampreys (Petromyzontidae) prey on these sharks in a parasitic relationship, whereby the lamprey attaches to the shark, and extracts blood and other nutrients through a wound. These sharks also have mutualistic relationships with pilotfish (Naucrates ductor), which clean their gills and, in exchange, get to eat the scraps of food left behind in the gills. ()

Grey nurse sharks are known for their fierce appearance and have gained an undeserved reputation as a man-eater in Australia. These sharks are not generally aggressive, but have been known to bite. Their bites can inflict serious damage because of their size and their dangerous teeth. They are sometimes tangled in fishing nets. ()

Shark teeth are lost frequently and are prized gifts in many regions of the world. Shark is a delicacy that is eaten in many areas. ()

Grey nurse sharks were the first shark species to be protected by law. Grey nurse sharks are cited as being critically endangered in the Commonwealth Legislation (Australia). They are also considered endangered in New South Wales. The Queensland Government is hoping to provide a listing in the Nature Conservation Act of 1992 which will give these sharks additional protection. The National Marine Fisheries service in the United States prohibits hunting of these sharks. The IUCN lists grey nurse sharks as a vulnerable species on the red list (last evaluated in 2000). CITES does not have a listing for them, and is the most recently updated (2005). The fact that these sharks live in shallow, accessible waters, have a fierce appearance, and have a low reproductive rate, has contributed to declines in populations. Population declines worldwide are estimated at 20% in the last 10 years. ()