Ragged Tooth Shark

The Ragged-tooth Shark is a large, coastal shark with an incredible appearance and extremely docile behaviour. The Ragged Tooth Shark, also referred to as Carcharias taurus, is found in all of the world’s oceans, including in subtropical and temperate waters.

It’s worth noting that, depending on the part of the world you find this shark, there are several other common names used to refer to this particular shark:

1.) Sand Tiger Shark (common name for Ragged Tooth Shark in the U.S.)
2.) Grey Nurse Shark (common name for Ragged Tooth Shark in Australia)
3.) Spotted ragged-tooth Shark (sometimes used as a common name for ragged-tooth shark in South Africa).

While the Ragged Tooth Shark appears to have long, sharp teeth that protrude from its mouth whether open or closed, they are non-aggressive and can be very slow-moving. The Ragged Tooth Shark does not seem aggressive towards people and will typically only defend itself when threatened or provoked. The fact that this shark has such a ferocious look and yet is so peaceful makes it possibly one of the most interesting shark species.

The Ragged Tooth Shark is primarily found in the shallower coastal regions of oceans, such as on reefs, rocky coastlines and other shallow structures and environments that provide a place for the shark to hide from predators and feed on a wide variety of fish, crustaceans, etc., as well as providing a place for the shark to breed.

Along the South African coastline, the Ragged Tooth Shark is typically seen in:

• Shallow low-tide reef systems
• Seabeds covered in sand adjacent to rocky outcrops
• Caves and crevices underwater
• Ledges and overhangs beneath the water’s surface
• Drop-offs that are steep and located close to the shoreline

It should be noted that while the Ragged Tooth Shark is typically associated with shallow water, the species has been found at depths from the wave zone to approximately 190 meters or greater.

Maximum reported lengths of Ragged Tooth Sharks are about 2.2 to 3.2 meters for large males or unsexed specimens.

The weight of the largest specimen was around 300 kilograms; some authors have rounded this to 159 kg for exceptionally large sharks (approximately 350 pounds).

Earlier research suggested that the average life span of the Ragged Tooth Shark is about 25 to 35 years in the wild. More recent and credible scientific studies, using vertebral growth band analysis, have indicated that the Ragged Tooth Shark can live much longer than earlier estimates.

Scientific evidence has validated a maximum life span of at least 40 years for females and an approximate life span of 40 years for males. The evidence indicates the Ragged Tooth Shark to be one of the longest-living coastal predators.

Sexual maturity in the Ragged Tooth Shark occurs much later than it does with other types of sharks. Sexual maturity has a significant impact on the population dynamics of the Ragged Tooth Shark.
Male Ragged Tooth Sharks reach sexual maturity at approximately 1.9 meters to 2.2 meters in total length, giving them many years to grow before they can reproduce. Female Ragged Tooth Sharks also reach sexual maturity at similar sizes to males and follow a unique reproductive strategy found among other members of the same family.

Unique Reproductive Methodology

The Ragged Tooth Shark is an example of an ovoviviparous fish, meaning the embryos develop inside eggs within the mother’s body. The embryo hatches internally before birth. What makes the Ragged Tooth Shark particularly interesting is intrauterine cannibalism (also referred to as oophagy) during embryonic development.

Intrauterine cannibalism involves several processes:

• Multiple embryos form in each uterus.
• The largest developing embryo consumes the remaining eggs and may also consume smaller embryos.
• Only one well-developed pup will be born per uterus.

Therefore, females give birth to only two pups at a time; one from each uterus.

How Slow Reproduction Affects Populations

Since the Ragged Tooth Shark produces few offspring, the species’ population grows slowly.

The low reproductive rate has two primary effects on populations:

• Recovering from reduced populations will take many years.
• Any overfishing or destruction of their habitats could cause long-term damage.
• Every mature individual plays a vital role in stabilising populations.

Long-lived adults, whose slow growth rates contribute to the late maturity of the Ragged Tooth Shark, are vital to the survival of the species. Therefore, protecting mature breeding individuals is critical to the continued survival of future generations of Ragged Tooth Sharks in coastal areas of South Africa and worldwide.

Understanding the environment in which the Ragged Tooth Shark exists will help to understand why it selects specific habitats, but identifying exactly where the Ragged Tooth Shark lives, from around the world and within South Africa, will give you an even better understanding of what makes up its behaviour and how far it moves seasonally.

Range of the Ragged Tooth Shark Globally

The Ragged Tooth Shark is located in tropical and temperate waters on the three major ocean basins:

• Indian Ocean
• Atlantic Ocean
• Pacific Ocean

Because of the wide range of the Ragged Tooth Shark, they are able to adapt to many different types of coastal environments. For the Ragged Tooth Shark to be successful, there needs to be a structure for the Ragged Tooth Shark to rest, and prey for the Ragged Tooth Shark to hunt. This species prefers areas on the continental shelf instead of open ocean waters and stays relatively near shore.

Range of the Ragged Tooth Shark in South Africa

On the South African coastline, the Ragged Tooth Shark is most commonly reported on the east coast of South Africa, primarily in the warm waters off KwaZulu-Natal. The combination of warm-water currents, reef systems, rocky outcroppings, and underwater cave systems provides an ideal environment for this species.

There are also numerous other coastal shark species that coexist with the Ragged Tooth Shark in these waters, contributing to a healthy and diverse marine ecosystem.

The Ragged Tooth Shark has been a major feature on South Africa’s coastlines for decades. The unique appearance and specialised features of the Ragged Tooth Shark distinguish it from other shark species.

Some of the most interesting aspects of the Ragged Tooth Shark include:

Distinctive “Ragged-Tooth” Distinguishing Features

• The Ragged Tooth Shark has an easily recognisable appearance due to its long, thin, needle-like teeth, which protrude out of its mouth even when its jaws are closed.
• Although the Ragged Tooth Shark may appear intimidating with its dramatic-looking teeth, it is known to be docile.

Unique Adaptation of Using Air-Gulping for Buoyancy Control

• One of the Ragged Tooth Shark’s most unique adaptations is its ability to suck in air at the surface and hold it in its stomach.
• The air stored in the stomach serves as a buoyant device, enabling the Ragged Tooth Shark to remain relatively still in the water column and thus conserving energy.

Use of Buoyancy-Controlled Hovering and Resting Behaviour

Due to the ability to use air-gulping as a buoyant device to maintain position in the water column, the Ragged Tooth Shark is able to:

• Hover over reefs and sandy bottoms with little effort
• Rest close to rocky formations and underwater caves
• Remain stationary near shipwrecks

Intrauterine (or Uterine) Cannibalism (Embryo Cannibalism)

Reproduction among the Ragged Tooth Shark is perhaps one of the most unique methods employed by any shark. Once pregnant, a female Ragged Tooth Shark:

• Will develop multiple embryos within her uterus.
• The stronger, better-developed embryo will consume its weaker, less-developed siblings.
• Generally, only one healthy pup develops in each uterus.
• As a result, a female Ragged Tooth Shark typically only births one or two pups during each reproductive event.

Slow Population Growth Rates

Because the Ragged Tooth Shark generates low amounts of young and matures late in life, populations grow slowly.

Therefore, the Ragged Tooth Shark is highly susceptible to overfishing, and habitat degradation will likely take longer to recover from, and conservation efforts need to be made as soon as possible.

Each mature individual of the Ragged Tooth Shark plays a significant role in maintaining population numbers, and therefore, conservation of the species is crucial.

A Friendly but Fearsome Species

Unlike its fearsome-looking teeth, the Ragged Tooth Shark is generally a slow-moving and calm creature and poses no threat to humans unless provoked or harassed.

This distinct contrast between the appearance of the Ragged Tooth Shark and its behaviour contributes to its status as one of the most interesting coastal shark species to study and observe in the waters off South Africa.

Why Ragged Tooth Sharks Matter in Ecosystems

The Ragged Tooth Shark is an apex predator, which means that it plays a vital role in regulating the food web and keeping ecosystems balanced. The way that this shark feeds on a variety of prey including bony fish, stingrays, squid and even other sharks, ensures that there are no individual prey populations that become too dominant in the environment, and provides a healthy, balanced food source for all other marine animals.

As well as providing a food source, the fact that the Ragged Tooth Shark rests in caves and along rock ledges also creates what is known as “habitat hot spots.” The presence of these resting sites can affect the behaviour of other marine species in the area and increase diversity at the site.

Due to the slow reproductive rate of the Ragged Tooth Shark, if there are changes to the environment, this can be reflected in the decrease in population of this shark. Therefore, declines in the Ragged Tooth Shark population can serve as indicators of problems in the wider ecosystem, including overfishing, habitat loss, and bycatch. This is why many scientists see the presence of healthy Ragged Tooth Shark populations as an indication of the overall health of the ocean.

Spotting, or studying, this type of shark generally requires a great deal of patience and knowledge regarding the preferences for its habitat and behavior.

• The easiest way to determine if you have spotted a Ragged Tooth Shark would be to examine its long, thin, pointed teeth (that can be seen sticking out of its mouth regardless of whether its jaws are closed). This gives it a distinctive look compared to many other coastal species of sharks.
• Behavioural characteristics of the Ragged Tooth Shark are also very useful when trying to determine if you have identified one. The shark will often remain still in one location or slow down as it moves over the bottom of the ocean. This has been linked to the sharks unique ability to gulp air into its body while remaining underwater, which will allow it to maintain a consistent level of buoyancy without expending much energy.

Sightings and studies of the Ragged Tooth Shark are also most prevalent on the Kwa-Zulu Natal coast of South Africa, where several local dive centres and marine research organisations study and track the movement of individual sharks throughout different times of the year.

When watching the Ragged Tooth Shark, always remember to follow safe diving practices. Keep your distance from sharks; do not disturb them when they are resting in a group, and follow all local regulations for the protection of sharks to ensure the safety of divers and sharks.

The ragged-tooth sharks are currently listed on the IUCN Red List as “Vulnerable”, which indicates that there are still declining numbers in many parts of it’s global range. It’s worse than vulnerable in certain areas. In fact, along the eastern part of Australia, this species is listed as “Critically Endangered” under the name Grey Nurse Shark. There are now fewer than one percent of the number of individuals of this species present today compared to when they were first recorded.

The major threats facing the ragged tooth shark are: overfishing (either intentionally caught or caught incidentally) and habitat loss/deterioration particularly from cave destruction and/or rocky ledge removal and also low reproduction rates. These combined threats will prevent any potential recovery of declining ragged-tooth shark populations.

The waters off Durban are one of the most diverse places on Earth in terms of shark species, and every year we continue to discover new shark behaviours, migrations, and predator dynamics that help us understand the incredible power of these predators.

Durban has many unique marine biodiversity areas, from coastal reefs to deeper offshore areas, providing endless opportunities to study sharks in their natural habitats. Visitors have the opportunity to experience the area’s diverse shark population through both educational marine tours and responsibly operated dive excursions, and to develop greater awareness and respect for ocean conservation and wildlife interactions.