Ragged Tooth Shark
The grey nurse shark (Australia), spotted ragged-tooth shark (Africa) or sand tiger shark (US and UK), Carcharias taurus, is a large shark inhabiting coastal waters worldwide, with many different names in different countries in the world. Despite a fearsome appearance and strong swimming abilities, it is a relatively placid and slow moving animal. It is considered not aggressive unless provoked. It is considered the most widely kept shark in public aquariums around the world, due to its fairly large size, its higher adaptability to captivity than other large sharks and its crooked, fierce-looking teeth.
Anatomy and appearance
The body is stout, with two large dorsal fins and the tail is elongated and has a long upper lobe. The shark has a precaudal pit but no caudal keels. It grows to a length of 3.5 m (about 11 ft). This shark weighs 90 to 160 kg (200 to 350 lb). A maximum weight of 300 kg (660 lb) has been reported. The grey nurse shark usually has a grey back and white underside. It also has grey dorsal fins. The males also have a grey reproductive organ with a white tip. In August 2007, an albino specimen was photographed off South West Rocks, Australia.
The diet of Carcharias taurus consists of fish, young sharks and rays, squid, and crustaceans.
The sharks typically congregate in coastal waters, at depths of between 60 and 190 m, although deeper depths have been recorded. Often they will shelter in caves or gutters during the day, and come out at night to feed. During the day they exhibit sluggish behavior, becoming more active during the night. The grey nurse shark is the only known shark to gulp and store air in its stomach in order to maintain neutral buoyancy while swimming. As of 2010 there have been 64 known attacks leading to 2 fatalities.
The species practices adelphophagy, a form of viviparity where the embryos eat each other. Female sharks have two uteri. Inside each uterus the young sharks develop and eat from the yolk sac and then each other until there are only two left, one in each of the uteri. To provide further nourishment , the mother continues to produce eggs that are eaten by her two remaining young. After two years the young are around 1 m long, miniature replicas of their mother and fully able to fend for themselves and she gives birth to them in a lengthy labour. There are reports of biologists probing the bellies of landed females and having their fingers nipped by the cannibalistic young with their fully developed teeth. This fascinating reproductive strategy, also known as intrauterine cannibalism is making it harder for the shark population to rebound from near extinction. As a result, scientists plan to artificially inseminate and breed the sharks, in order to increase their population. Another plan is to remove the shark embryos from the uterus before cannibalism can take place and then artificially gestate them.
It is listed as vulnerable on the IUCN Red List, and as endangered under Queensland's Nature Conservation Act 1992. It is a U.S. National Marine Fisheries Service Species of Concern. Species of Concern are those species about which the U.S. Government’s National Oceanic and Atmospheric Administration, National Marine Fisheries Service (NMFS), has some concerns regarding status and threats, but for which insufficient information is available to indicate a need to list the species under the U.S. Endangered Species Act. For further information on conservation status and measures, see grey nurse shark conservation.
See Ragged Tooth Sharks on our South African Shark Diving Adventure
See the other sharks:
- Great White Shark
- Hammerhead Shark
- Mako Shark
- Tiger Shark
- Zambezi Shark
- hale Shark