The Ragged Tooth Shark (Carcharias taurus) is also known as the Sand Tiger Shark, Spotted Ragged Tooth Shark, Blue Nurse Sand Tiger and a Grey Nurse Shark.
Although rather frightening in appearance, this species is relatively placid and docile, only likely to make an attack if cornered or provoked. Because of it’s somewhat scary look and its slow, passive movements, this is the ideal shark for a manmade aquarium, and can often be seen on display in such facilities all over the world.
Ragged Tooth Shark Appearance
The Ragged Tooth Shark ranges in length from 2m (6.6 feet) to 3.2m (10.5 feet) and in weight from 91 kg (201 lb) to 159 kg (351 lb). The head is pointed and not round, and the snout is flattened, or conical in shape. The eyes of the Ragged Tooth Shark are very small, without any eyelids.
In males, grey claspers with white tips are located on the lower side of body, and the caudal fin is extended with a long upper lobe. They have two large grey dorsal fins with a wide base behind the pectoral fins. Adults often have brownish-red specks on their back end with the rest of their body being a greyish-brown, with a lighter belly.
In August 2007 an albino specimen was photographed near the South West Rocks in Australia. The teeth of these sharks do not have any transverse serrated edges like that of many other sharks.
Instead, the Ragged Tooth has a rather smooth and larger main cusp with smaller cusplets on each side of the main cusp. Upper front teeth are separated by small intermediate teeth on each side of the mouth which makes for a really unique smile!
Buoyancy Of The Ragged Tooth Shark
The Ragged Tooth Shark is very different from other sharks in terms of its buoyancy. Most species remain buoyant by the large amount of oil in their large liver, which is lower in density than the water around them.
However, in the case of Ragged Tooth Sharks, they gulp down and keep air in their stomachs to keep them from rolling over or sinking to the bottom of the ocean.
Ragged Tooth Shark Habitat
The Ragged Tooth Shark is found in all three of the major oceans (Atlantic, Pacific, Adriatic and Indian Ocean) and in the Mediterranean Sea every so often. They prefer the shallower coastlines and reefs, but can actually be found at all depths.
Ragged Tooth Sharks roam in epipelagic (the upper level of the sea) and mesopelagic (slightly deeper at around 200 metres – 650 feet) levels of the sea. This means that they enjoy staying around sandy, coastal waters, estuaries, shallow bays, and rocky or tropical coral reefs up to 190 metres (or 623 feet) deep.
In the Western Atlantic Ocean they can be found in coastal waters from the Gulf of Maine to Florida. They are also often spotted on the northern Gulf of Mexico to the Bahamas, Bermuda, Southern Brazil and northern Argentina.
In the Eastern Atlantic Ocean they have been seen from the Mediterranean to the Canary Islands, Cape Verde, along the coasts of Senegal and Ghana and from southern Nigeria to Cameroon.
In the Western Pacific, they have been located off the coastlines of Japan and Australia, however they do not tend to go as far as New Zealand.
The Western Indian Ocean is home to Ragged Tooth Sharks from South Africa to southern Mozambique, but avoid going to Madagascar. Ragged Tooth Sharks have also been reported as far as the Red Sea and can be found even in some of the far eastern regions of India.
Behaviour Of The Ragged Tooth Shark
This Ragged Tooth Shark is a nocturnal animal and spends the day times hidden in caves and gutters, paying little attention to divers. They make little or no effort or exertion during the day, conserving their energy for their night-time hunting.
This shark sticks to relatively shallow depths of around 200 metres (650 feet). It is the only shark known to swallow air and keep it in its belly, which allows the shark to maintain a close to neutral buoyancy and hunt very still and silently.
Ragged Tooth Shark Diet
Most of the prey of the Ragged Tooth Shark are from the sea floor (this is called demersal prey). This consists of bony fish (teleosts) that make up about 60% of their standard diet. The remaining percentage consists of larger prey that includes other smaller sharks and rays (for example the smaller Smoothhound Shark).
They catch a wide variety of different species of prey, from the surf to the continental shelf, which indicates the truly opportunistic hunting nature of the Ragged Tooth Shark.
Mating & Ragged Tooth Shark Courtship
Females tend to hover just above the sandy ocean floor when susceptible. Sometimes there is more than one male nearby, with the dominant one close to the female intimidating others with an aggressive look. The dominant male shark follows the tail of the subordinate and forces the subordinate to accelerate and swim away.
The dominant male bites at smaller fish and other species to scare them away. The male approaches the female, and the couple then guard the sandy bottom on which they interact with each other.
The male shows an interest with superficial bites of the females anal and pectoral fins, in which the female responds with a shallow bite on the males body.
The behaviour continues for several days, during which time the male patrols the area around the female. The male frequently approaches the female and ‘noses’ the cloaca to ‘sniff’ it.
When they are ready to mate, and the female is fully submissive, the couple roll around together, contorting their bodies, until the males’ claspers enters the female cloaca. This turns into a very aggressive act with he male biting the base of the females right pectoral fin, leaving easily visible wounds and scars afterwards.
The whole mating process only takes a few minutes, then the two separate and the male leaves. The female shark will often take on several male partners as the female will only mate every 2-3 years. At the end of the mating season, you can often find groups of almost exclusively female sharks along the coastline.
Ragged Tooth Shark Migration
The Ragged Tooth Shark is found on the southern and eastern coasts of South Africa.
In November/December they mate at coral reefs in the north of the Eastern Cape and in the southern waters of Kwa Zulu-Natal and then travel north to southern Mozambique to breed in warmer waters, and return to Cape East (south of the Cay River) to give birth. Some females only breed once every two years.
Scientists were able to obtain more detailed information about the movement of Ragged Tooth Sharks along and down the South African coast with satellite and ultrasonic tags.
Teeth Of The Ragged Tooth Shark
The name of this shark comes from the vicious looking teeth. The teeth are like needles, rather than being serrated. These seize the prey, which is then swallowed whole. Favoured meals include bony fish, other sharks, rays, crustaceans and squid. Underneath a picture that shows the teeth of a Ragged Tooth Shark.
Reproduction Of The Ragged Tooth Shark
Mating occurs in the northern hemisphere around August and December and in the southern hemisphere around August-October.
The Ragged Tooth Shark is Ovoviviparous, meaning that eggs are fertilised and hatched inside the mother and that the pups continue to live internally until they are big and strong enough to be born alive.
The mother continues to produce unfertilised eggs inside her uterus so that the pups have sustenance while they are yet to be born, essentially making them cannibalistic (this is a process known as oophagy). Only two pups are born (one from each uterus) and they each measure approximately 100 cm at birth.
Cartilaginous fish (including sharks, skates and rays) reproduce in three ways:
Oviparous – The female lays an egg called the ‘mermaid purse’, which can often be washed ashore. This egg case contains a the embryo and yolk, and eventually a young shark hatches from this case. Cat sharks and shy sharks are Oviparous.
Ovoviviparous – This is where the embryo hatches from the egg into the uterus and feeds on the yolk sac until birth. Ragged Tooth Sharks are Ovoviviparous.
Viviparous – A Viviparous birth is when the embryo grows in the uterus and is fed through the placenta and on milk from the uterus. Hammerhead and great white sharks are viviparous. This is much like a humans reproduction process. Examples of Viviparous sharks include the Hammerhead and the Great White Shark.
Is the Ragged Tooth Shark Dangerous?
While considered to be one of the more passive sharks in today’s oceans, the Ragged Tooth Shark has nevertheless been known to make attacks on humans, with a very small percentage of fatalities. This acts as an important reminder of the capabilities of these fish and the respect they command.
Ragged Tooth Sharks are threatened all over the world because they slowly enter sexual maturity, give birth to few offspring and are highly vulnerable to overfishing due to their coastal habits.
Ragged Tooth Shark populations in Australia and the United States have declined dramatically due to overfishing. In 1984, Australian Ragged Tooth Sharks became the first protected shark species.
Today, they are also protected in the United States, while they can not be sold without a commercial permit in South Africa.
A working group of the International Union for Conservation of Nature stated in 2003 that the state of the population of Ragged Tooth Sharks in South Africa was ‘under threat’, but the actual population size is unknown and currently being investigated.