SAND TIGER SHARK OR SPOTTED RAGGEDTOOTH SHARK
A shark with a menacing ragged-tooth appearance
The Sand Tiger shark (Carcharias taurus), or sometimes called the Grey Nurse shark, or Spotted Raggedtooth shark is a shark belonging to the family Odontaspididae, belonging to the order Lamniformes. Other names include the Blue Nurse Sandtiger shark. They inhabit subtropical and temperate waters worldwide from coastal waters to the surf zone over submerged reefs to a depth of around 627 ft. Despite its fearsome appearance and strong swimming ability, it is a relatively docile and placid and slow-moving shark with no confirmed human fatalities. It will defend itself if necessary, though. They are a much studies shark in captivity and in the wild, and have several social and behavioral traits unique and complex to them. Read below to find out more.
Family: Odontaspididae – Sandtiger sharks
Common Name– Mackerel Sharks
Common Name– Sandtiger Sharks
Average Size and Length: They are born between 95-105 cm/3.1-3.5 feet. Mature sharks have been measured around 220 cm/7.2 feet. The maximum length has been over 430 cm/14.1 feet.
Average Weight: They have been recorded to weigh anywhere from 201 pounds to 351 pounds.
Current Rare Mythical Sightings: The Sand Tiger shark was described as Carcharias taurus by Constantine Rafinesque from a specimen caught off the coast of Sicily. There have been a number of disputes and re-classification attempts over the years, but the current name still stands.
Teeth and Jaw: The mouth is long, and it extends behind the eyes. The teeth are large, slender and pointed. A Sand Tiger shark usually swims with its mouth open displaying three rows of protruding, smooth-edged, sharp-pointed teeth. The teeth have no transverse serrations but they have a large, smooth main cusp with a tiny lateral cusplet on each side of the main cusp. The upper front teeth are separated from the teeth on the side of the mouth by small intermediate teeth. The upper teeth number 44 to 48 and the lower teeth number 41 to 46. The teeth in the corners of the mouth are small and many. Based on the description and their appearance of their teeth, this is where their name Spotted Raggedtooth shark came from.
Head: They have a flattened and conical snout. The eyes are small, lacking eyelids.
Denticles: The dermal denticles of the Sand Tiger shark or Spotted Raggedtooth shark are loosely spaced and ovoid lanceolate shaped with three ridges. The axial ridge is prominent and sharp-edged anteriorly but usually is subdivided and flat-topped posteriorly. In individuals around 3.3 feet long denticle sizes are about 0.016 inches broad by 0.018 inches long.
Demographic, Distribution, Habitat, Environment and Range: The Sand Tiger shark or the Spotted Raggedtooth shark prefers warm, temperate and tropical seas. They can be found in the Atlantic, Mediterranean, and the Indo-west Pacific. They can be found in coastal waters from the surf zone (less than 3 feet) to offshore reefs of at least 627 feet. They mostly stay between 49-82 feet. They are connected with underwater caves, gullies and reefs. They are usually on or near the bottom and occasionally in midwater or at the surface. They are epipelagic and mesopelagic.
In the Western Atlantic Ocean, it is found in coastal waters around from the Gulf of Maine to Florida, in the northern Gulf of Mexico around the Bahamas and Bermuda, and from southern Brazil to northern Argentina. It is also found in the eastern Atlantic Ocean from the Mediterranean Sea to the Canary Islands, at the Cape Verde islands, along the coasts of Senegal and Ghana, and from southern Nigeria to Cameroon. In the western Indian Ocean, it ranges from South Africa to southern Mozambique, but excluding Madagascar. They have also been sighted in the Red Sea, and maybe even as far east as India. In the western Pacific, it has been sighted in the waters around the coasts of Japan and Australia, but not around New Zealand.
Some Sand Tiger sharks or Spotted Raggedtooth sharks are highly migratory, moving to cooler water in the summer. This is the South African population, which may cover more than 620 miles, and round-trip of 1,900 miles. They pup during the summer in relatively cold water around 61 °F. After parturition, they swim northwards toward sites where there are suitable rocks or caves, often at a water depth of around 66 feet. This is where they mate, which is during and after the winter. Being nocturnal, they also typically mate at night. After they mate, they swim further north to even warmer water where gestation takes place. In the Autumn they return southwards to give birth in cooler water. Young shark may move deeper into the ocean while the adult sharks take part in the annual migration.
At Cape Cod, juveniles move away from coastal areas when water temperatures decrease below 61 °F and day length decreases to less than 12 hours. Juveniles, however, return to their usual summer spot, and as they become mature, they engage in migratory patterns that are larger ranges.
Diet: They feed on a wide range of fish and invertebrates. They have complex social feeding aggregations and techniques. The majority of prey items of sand tigers are demersal, suggesting that they hunt extensively on the sea bottom as far out as the continental shelf. 60% of prey is bony fish. They have also been known to prey upon smaller sharks. Based on the data of stomach contents of various sharks, smaller sharks may prey on smaller bottom fish and organisms, and larger sharks, larger benthic prey. Some populations have been observed taking prey about half their size. Prey is typically swallowed in 3 or 4 chunks.
Aesthetic Identification: The Sand Tiger shark or Spotted Raggedtooth shark are large, heavy and grey to light brown, with scattered darker spots. The ventral side is pale. The long gill openings are in front of the pectoral fins. The large dorsal and anal fins are similar in size. The dorsal fins are broad. The first dorsal fin is closer to the pelvic fins than to the pectoral fins. The males have grey claspers with white tips located on the underside of their body.
The most likely problem when identifying the Sand Tiger shark or Spotted Raggedtooth shark is when in the presence of either of the two species of Odontaspis (the Bigeye Sandtiger and the Smalltooth Sandtiger). Firstly, the Sand Tiger shark is usually spotted, especially on the hind half of the body. The second dorsal fin of the Sand tiger shark or Spotted Raggedtooth shark is almost as large as the first dorsal fin. The first dorsal fin of the Sand Tiger shark is relatively non-symmetric. The first dorsal fin of the Sand Tiger shark is closer to the pelvic fin than to the pectoral fin.
In August 2007, an albino specimen was photographed off South West Rocks, Australia.
Biology and Reproduction: Two pups are born every other year, one from each uterus. The surviving embryo kills and eats the smaller embryos and feeds on unfertilized eggs during 8-12-month gestation period. This is called intrauterine cannibalism. Since they give birth only every second (or even third) year, resulting in an overall mean reproductive rate of less than one pup per year, one of the lowest reproductive rates for sharks.
Mating happens around March and April in the northern hemisphere and during August through October in the southern hemisphere.
The courtship and mating of Sand Tiger sharks 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 behavior continues for several days during which the male patrols the area around the female. The male regularly approaches the female in “nosing” behavior 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 sharks separate. (Gordon, I. (1993). “Pre-copulatory behaviour of captive sandtiger sharks, Carcharias taurus“. Environmental Biology of Fishes. 38: 159–164).
Females often mate with more than one male and 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 Sand Tiger shark populations comprising almost exclusively females. (Bansemer, C. S.; Bennett, M. B. (2009). “Reproductive periodicity, localised movements and behavioural segregation of pregnant Carcharias taurus at Wolf Rock, southeast Queensland, Australia“. Marine Ecology Progress Series. 374: 215.)
During the first year, they grow about 27 cm to reach 4.3 feet. After that, the growth rate decreases by about 2.5 cm each year until it stabilizes at about 7 cm/y. Males reach sexual maturity at an age of five to seven years and approximately 6.2 feet in length. Females reach maturity when approximately 7.2 feet long at about seven to ten years of age. (Branstetter, Steven; Musick, John A. (1994). “Age and Growth Estimates for the Sand Tiger in the Northwestern Atlantic Ocean“. Transactions of the American Fisheries Society. 123 (2): 242.)
Behavioral Traits, Sensing and Intelligence: They are nocturnal, active at night.
The Sand Tiger shark or Spotted Raggedtooth shark has complex social courtship and mating behavior. It has been studied in captivity, and in the wild.
They may aggregate in schools of 20-80 for feeding, courtship, mating and birth. One observation has been to herd fish that is to be prey.
Speed: They are slow, but strong swimmers. They swallow air at the surface and hold it in their stomachs, which provides neutral buoyancy. This enables the shark to hover in the water.
Sand Tiger Shark Future and Conservation: They are listed as vulnerable. Many populations have been perilously depleted. In NSW and Australia, they are critically endangered due to large numbers of sharks being killed in commercial fisheries and sport fishing, and even by divers. In many countries they are legally protected.
Sand Tiger sharks or Spotted Raggedtooth sharks are commonly kept in public aquaria around the world and are bred in captivity. They have been found to be highly susceptible to developing spinal deformities, with as many as one in every three captive sharks being affected, giving them a hunched appearance. These deformities have been hypothesized to be correlated to both the size and shape of their tank. If the tank is too small, the sharks have to spend more time actively swimming than they would in the wild, where they have space to glide. In small, circular tanks often spend most of their time circling along the edges in only one direction, causing asymmetrical stress on their bodies. (Tate, Erin E. (2013). “Correlations of Swimming Patterns with Spinal Deformities in the Sand Tiger Shark, Carcharias taurus“. International Journal of Comparative Psychology. 26: 75–82.)
They are important for ecotourism and dive ecotourism in Australia and South Africa, and in North Carolina. In North Carolina many tech divers travel from around the world to see them gather in and around offshore shipwrecks.
In Australia and South Africa, one of the common practices in beach holiday areas is to place shark nets around the beaches frequently used by swimmers. These nets are established around 1,300 feet from the shore and act as gill nets that trap incoming sharks. This was common practice until 2005. This caused a significant decline in the South African population, and due to their slow reproduction rates, the population has not stabilized and or increased. Prior to 2000, nets have killed an average of 200 Sand Tiger sharks per year. 40% were reported to survive and released.
In some locations, like Argentina, humans and sharks’ prey upon the same fish, and therefore the sharks have to compete with us for hood. This has caused a decline in those populations.
Estuaries along the United States of America’s eastern Atlantic coast houses many of the young Sand Tiger sharks. These estuaries are susceptible to non-point source pollution that is harmful to the pups.
Sand Tiger sharks are often the targets of scuba divers who wish to observe or photograph these animals. A study near Sydney in Australia found that the behavior of the sharks is affected by the proximity of scuba divers. Diver activity affects the aggregation, swimming and respiratory behavior of sharks, but only at short time scales. The group size of scuba divers was less important in affecting sand tiger behavior than the distance within which they approached the sharks. Divers approaching to within 3 m of sharks affected their behavior but after the divers had retreated, the sharks resumed normal behavior. (Barker, S. M.; Peddemors, V. M.; Williamson, J. E. (2011). “A video and photographic study of aggregation, swimming and respiratory behaviour changes in the Grey Nurse Shark (Carcharias taurus) in response to the presence of SCUBA divers“. Marine and Freshwater Behaviour and Physiology. 44 (2): 75.)
Sand Tiger Shark Recorded Attacks on Humans: They are considered docile and aren’t a threat to humans, unless provoked or threatened. They could bite if approached too closely. One unborn pup bit an investigating scientist.