The grey nurse shark, the name used in Australia and the United Kingdom, is the second-most used name for the shark, and in India it is known as blue-nurse sand tiger. The most unambiguous and descriptive English name is probably the South African one, spotted ragged-tooth shark, or scientifically as Carcharias taurus. Also colloquially known as Raggies.

They are often associated with being vicious or deadly, due to its relatively large size and sharp, protruding teeth that point outward from its jaws. These sharks are however quite docile, and are not a threat to humans. Their mouths are not large enough to cause a human fatality. Raggies roam the surf, sometimes in close proximity to humans, and there have been only a few instances of unprovoked shark attacks on humans, usually associated with spear fishing, line fishing, or shark feeding.

Physical characteristics and appearance

This species has a sharp, pointy head, and a bulky body. The can grow to a length can reach 3.2 m. They are grey with reddish-brown spots on their backs.

Their diet consists of bony fish, crustaceans, squid, skates and other sharks. Unlike other sharks, they can gulp air from the surface, allowing it to be suspended in the water column with minimal effort. During pregnancy, the most developed embryo will feed on its siblings, a reproductive strategy known as intrauterine cannibalism i.e. "embryophagy" or, more colorfully, adelphophagy—literally "eating one's brother".

Behaviour

Raggies in South Africa undertake an annual migration that may cover more than 1,000 km. Raggies are nocturnal feeders. During the day, they take shelter near rocks, overhangs, caves and reefs often at relatively shallow depths. This is the typical environment where divers encounter them, hovering just above the bottom in large sandy gutters and caves. However, at night they leave the shelter and hunt over the ocean bottom, often ranging far from their shelter. They hunt by stealth and are the only shark known to gulp air and store it in the stomach, allowing the shark to maintain near-neutral buoyancy which helps it to hunt motionlessly and quietly. Aquarium observations indicate that when it comes close enough to a prey item, it grabs with a quick sideways snap of the prey.

Reproduction

Raggie mating occurs around August–October in the southern hemisphere. The courtship and mating has been best documented from observations in large aquaria. In Oceanworld, Sydney, the females tended to hover just above the sandy bottom ("shielding") when they were receptive. This prevented males from approaching from underneath towards their cloaca. Often there is more than one male close by with the dominant one remaining close to the female, intimidating others with an aggressive display in which the dominant shark closely follows the tail of the subordinate, forcing the subordinate to accelerate and swim away. The dominant male snaps at smaller fish of other species. The male approaches the female and the two sharks protect the sandy bottom over which they interact. Strong interest of the male is indicated by superficial bites in the anal and pectoral fin areas of the female. The female responds with superficial biting of the male. This behaviour continues for several days during which the male patrols the area around the female. The male regularly approaches the female in "nosing" behaviour to "smell" the cloaca of the female. If she is ready, she swims off with the male, while both partners contort their bodies so that the right clasper of the male enters the cloaca of the female. The male bites the base of her right pectoral fin, leaving scars that are easily visible afterwards. After one or two minutes, mating is complete and the two separate. Females often mate with more than one male. Females mate only every second or third year. After mating, the females remain behind, while the males move off to seek other areas to feed, resulting in many observations of Raggie populations comprising almost exclusively females.

Protection status

They are categorized as vulnerable on the International Union for Conservation of Nature Red List. It is the most widely kept large shark in public aquariums owing to its tolerance for captivity. They are listed in the South African National Environmental Management: Biodiversity Act (10/2004) in terms of Section 56(1) and may not be targeted, caught or killed.