ColinYou must have come across images of these ferocious looking sharks. The sand tiger shark (Carcharias taurus), also known as the grey nurse shark, spotted ragged-tooth shark, or blue-nurse sand tiger is a species of shark that inhabits subtropical and temperate waters worldwide and can be found in the waters around Japan, Australia, South Africa, the Mediterranean and the east coasts of North and South America.
It inhabits the continental shelf, from sandy shorelines (hence the name sand tiger shark) and submerged reefs to a depth of around 627 ft / 191 m.
Species
Despite its name, it is not related to the tiger shark. Tiger sharks are bigger, have a pattern of spots and stripes, which give them their name, and more rounded snouts. Sand tiger sharks have pointed snouts and have reddish spots on their backs.It is rumored that aquariums are the source of the “tiger” in the sand tiger name. Originally called sand sharks, the tiger was added to make them seem more ferocious. However, it is a cousin of the great white shark.
There are four species of sand tiger sharks – the Indian sand tiger shark, the small-toothed sand tiger shark, the large-eyed sand tiger shark and simply the sand tiger shark.
The sand tiger shark is known by other names, such as the grey nurse shark or blue nurse sand tiger, the spotted ragged-tooth shark, slender-tooth shark, ground shark and in South Africa it is often referred to as a “Raggie”.
Sand tiger sharks may look fearsome but they are relatively placid and slow-moving sharks with no confirmed human fatalities. The species has a sharp, pointy head, and a bulky body. All sharks in this family swim slowly with their mouths open, exposing long, narrow, needle-like teeth. A fearsome sight, indeed!
At birth, a sand tiger shark is about 3 ft / 90cm long, doubling its length in five to ten years. On average, they can reach a full length of 10.5 ft / 3.2 m and weigh between 200 to 350 lbs / 90 to 160 kg. As in most sharks, the females are larger because they have to be able to carry their eggs.
Hunting
The sand tiger shark is a nocturnal feeder. During the day, they take shelter near rocks, overhangs, caves, and reefs often at relatively shallow depths (<65 ft / <20 m). This is the typical environment where divers encounter sand tigers, hovering just above the bottom in large sandy gutters and caves. However, at night they leave their shelter and hunt over the ocean bottom, often ranging far from their shelters. Sand tigers hunt by stealth. It is the only shark known to gulp air at the surface and store it in its stomach, allowing them to maintain near-neutral buoyancy which helps it to hunt motionlessly and quietly.
Breathing
Like all fishes, sharks breathe through their gills and they have two different methods of doing so – buccal pumping and ram ventilation. Buccal pumping means the shark pulls water into its mouth and then pumps it over its gills using its powerful cheek muscles. Ram ventilation means that as the shark moves forward, it takes in water and rams it through its gills. Ram ventilators need to move constantly in order to breathe, which is why you don’t see great white sharks keeping still.
Migration
Sand tigers in South Africa and Australia undertake an annual migration that may cover more than 620 mi / 1000 km. They pup during the summer in relatively cold water. After parturition, they swim northwards toward sites where there are suitable rocks or caves, often at a water depth of ca. 66 ft / 20 m, where they mate during and just after the winter. Mating normally takes place at night. After mating, they swim further north to even warmer water where gestation takes place. In the Autumn they return southwards to give birth in cooler water. This round trip may encompass as much as 1900 mi / 3000 km. The juvenile sharks do not take part in this migration, but they are absent from the normal birth grounds during winter: it is thought that they move deeper into the ocean.
Threats to sand tiger sharks
Sand tiger sharks are listed as endangered on the IUCN Red List. They are protected in the United States, Australia, and New Guinea. There are several factors contributing to the decline in the population of the sand tigers.
- Sand tigers reproduce at an unusually low rate, due to the fact that they do not have more than two pups at a time and because they breed only every second or third year.
- This shark is a highly prized food item in the western northern Pacific, off Ghana and off India and Pakistan where they are caught by fishing trawlers, although they are more commonly caught with a fishing line.
- Sand tigers’ fins are a popular trade item in Japan.
- In North America, it is fished for its hide and fins.
- Shark liver oil is a popular product in beauty products such as lipstick.
- It is sought by anglers in fishing competitions in South Africa and some other countries.
- In Australia it has been reduced in numbers by spearfishers using poison but fortunately it is now protected.
- It is also prized as an aquarium exhibit in the United States, Europe, Australia and South Africa because of its docile and hardy nature.
