By Dr Jade Maggs, Marine Scientist…
Spotted ragged-tooth Carcharias taurus, otherwise known as grey nurse sharks or sand tiger sharks are large, predatory animals. They are light brown, with small, irregularly spaced, dark brown spots. They have small eyes and the large mouth bears several prominent teeth, which are ragged in appearance.
DISTRIBUTION: Widely distributed in the warm-temperate and sub-tropical coastal shelf waters of the Indo-West Pacific, the Mediterranean, as well as the eastern and western Atlantic. Does not occur in the eastern and central Pacific Ocean.
HABITAT: Varied and may be found off sandy beaches as well as high profile reefs down to 200 m depth. Preferred habitat includes rocky caves and sand gullies along inshore reefs and islands in a water depth of 10-40 m. Mostly found close to the the seafloor, but can move through the water column.
BIOLOGY: A large, slow-growing species, which may live for up to 40 years. Has been recorded up to 326 cm and 253.8 kg in South Africa. Usually occurs in aggregations of 20-80 individuals, but may also occur in isolation. They are opportunistic feeders, preying on a wide variety of animals, including bony fish, rays, squids, crabs, lobsters and even smaller sharks. This species may also work cooperatively to concentrate prey before attacking.
This species is ovoviviparous, meaning that the female produces eggs, but the eggs hatch within the body before birth of the young. The reproductive strategy is fairly unique in that cannibalism takes place within the female’s uterus (plural uteri). Females actually have two uteri and, because of the cannibalism, only one pup is born per uterus. This is referred to as intra-uterine cannibalism. Ragged-tooth sharks, therefore, only ever produce two pups per litter, resulting in slow population growth.
MOVEMENT: Migratory, but the scale and nature of the migration may vary between populations. In South Africa and in the USA, migration is size and sex specific.
BEHAVIOUR: Ragged-tooth sharks are ambush predators, meaning that they move slowly towards unsuspecting prey before launching a short-range attack at lightning speed. This species should be treated with caution and should not be aggravated by divers.
CONSERVATION STATUS: Currently categorised as “vulnerable” on the IUCN Red List of Threatened Species. This species is not resilient to fishing pressure due to the slow population growth.