Living in South Africa, I never knew what a sand tiger shark was, let alone what it looked like until I discovered that the ragged tooth and the sand tiger are one and the same.
The South African name for the sand tiger is the spotted ragged-tooth, which sums up its appearance far better than its other names.
Also known as the grey nurse shark, it has very little in common with other nurse sharks, nor is it related to the tiger shark.
With a mouth jam-packed with protruding teeth, the sand tiger looks terrifying, especially when you’re underwater with them.
Fortunately for myself and others who’ve dived with sand tiger sharks, they’re generally harmless, but that doesn’t make them any less fascinating.
This intriguing species has a few unusual adaptations that both intrigue me and differentiate it from other shark species.
What Do Sand Tiger Sharks Look Like?
The most prominent characteristic of the sand tiger shark is its teeth.
With nearly 100 teeth in its mouth, it appears there’s simply not enough room for them all, causing the front rows to protrude out of the shark’s mouth in a random and menacing pattern.
If you can get past the tangle of teeth, you’ll notice that the sand tiger shark has a conical snout and a rather bulky appearance. Their bodies are brownish-grey on top and white underneath with a sprinkling of rust-colored spots.
Although sand tiger sharks have the same fins as most other sharks, their size and arrangement create a distinct profile.
On most sharks, the second dorsal fin is much smaller than the first, but this isn’t the case with the sand tiger. Both dorsal fins are around the same size, as are the prominent anal fins.
The sand tiger shark also has a distinct caudal fin, or tail, with an enlarged upper lobe that is notched just below the tip.
Just behind the sand tiger shark’s eyes are two small holes known as spiracles. The shark uses these to suck water over its gills, so it can continue breathing even when stationary.
Sand Tiger Shark’s Taxonomy
Sand tiger sharks are a species of mackerel shark. They belong to the order Lamniformes and numerous other sharks, including the great white and the prehistoric goblin shark.
The Lamniformes order contains seven different families, of which sand tiger sharks belong to the Odontaspididae family.
The three species of sand tiger sharks are the only living sharks within the Odontaspididae family, although it once contained numerous prehistoric species that have since gone extinct.
The sand tiger shark is closely related to the bigeye sand tiger, also known as the Odontaspis noronhai.
It was also thought to be a close relative of the smalltooth sand tiger shark or Odontaspis ferox. However, recent genetic studies indicate that the latter descended from a different ancestor, indicating that the “O. ferox did not group with Carcharias taurus and so the taxonomic classification of Odontaspididae needs to be revised.”
The sand tiger shark’s scientific name, Carcharias taurus means “bull shark,” which is somewhat misleading as it has no close association with the true bull shark or Carcharhinus leucas.
Sand Tiger Sharks’ Characteristics
The sand tiger is a large shark, averaging between seven and ten feet long. Both the big eye and small tooth sand tiger get even bigger, with the big eye measuring around 12’ long and the small tooth reaching lengths up to 14.8’.
None of these sharks are particularly speedy, usually traveling at around 1.41 kph. This is slightly slower than the great white shark, which usually cruises at around 3.2 kph.
Evidence suggests that sand tiger sharks can hit speeds of nearly 20kph for brief periods, most probably when hunting.
The sand tiger shark has some unique adaptations that set it apart from all other sharks. One of its most defining characteristics is its ability to use air to maintain neutral buoyancy.
Most sharks rely on their large, oily livers to control their buoyancy, but not the sand tiger.
It swims to the surface of the water and gulps in mouthfuls of air which it stores in the front section of its stomach. The shark then uses this as a “kind of built-in swim bladder or buoyancy compensator.”
By releasing air from its mouth or gill slits, a sand tiger shark can float motionless in the water without having to swim to maintain buoyancy.
Studies suggest that this behavior is exclusive to the sand tiger shark and has not been observed in the smalltooth sand tiger shark, presumably because its preference for deeper water makes the adaptation impractical.
Another distinctive characteristic of the sand tiger shark is displayed before the shark is even born.
Sand tiger sharks are one of the only species to practice intrauterine cannibalism.
In other words, the strongest embryos start hunting inside the uterus, getting the nutrition they need by eating their siblings.
Sand Tiger Sharks’ Life Cycle
Sand tiger sharks take several years to reach sexual maturity. Males need to be around 6 to 7 years old and reach a length of approximately 6 feet long before they’re ready to reproduce.
As is common in the world of sharks, the females take even longer. They only mature at around 9 to 10 years old, measuring approximately 7 to 7.5’ long.
Sand tiger sharks reproduce by internal fertilization. Females will mate with multiple males in a process known as polyandry. It’s thought this could contribute to the cannibalistic behavior of the embryos, with each male’s offspring fighting for survival.
Although the female sand tiger shark carries hundreds of eggs, it only ever gives birth to offspring – one from each uterus.
A yolk egg sac initially provides nutrition for these dominant embryos, but once that’s finished, they turn on their brothers and sisters.
After a 12-month gestation period, the two large shark pups are born. Measuring approximately 3’ long, they’re bigger than “baby whale sharks and almost as big as great white sharks.”
Some experts say this demonstrates “the ultimate in parental care.” Not only are the pups large, but they’re also “aggressive enough to survive in the wild.”
Wikipedia claims that the sand tiger shark lives only to around 7 years old, which would mean that all the females died before reaching sexual maturity.
Other estimates suggest that they may live for between 15 to 40 years, which is more consistent with other shark species.
Where do Sand Tiger Sharks Live?
Sand tiger sharks can be found globally in both tropical and temperate water. It lives in the Atlantic, Indian, Pacific Oceans, and the Adriatic and Mediterranean Seas.
Here in South Africa, it’s a relatively common shark along both the Southern and Eastern coasts.
They give birth in the cold waters around Cape Town before heading north to mate in the warmer waters around KwaZulu Natal.
Sand tiger sharks prefer shallow, coastal waters, especially as juveniles, but will also utilize rocky reefs and underwater caves.
Although they are usually found in shallow water, sand tiger sharks will swim down to depths of around 650 feet and can sometimes be found resting on the bottom.
Although juvenile sand tiger sharks will utilize nursery areas, they also perform “extensive seasonal coastal migrations.” In the US, they tend to hang out between Maine and Delaware Bay during the summer before moving south towards the area between Cape Hatteras and central Florida.
As an inshore species, sand tiger sharks come close to land, often cruising the surf zone in search of prey.
Sand Tiger Shark Behavior
For a long time, researchers believed the sand tiger shark to be a largely solitary creature that socialized with others only for specific purposes, like breeding.
By tagging the sharks, researchers at the University of Delaware managed to gain more accurate insights into how they live and who they hang out with.
According to their results, “the sharks were found to spend up to 95 consecutive hours together.” They also found that the size and composition of groups of sand tiger sharks change throughout the year.
For instance, males and females appear to take different migratory routes and don’t necessarily travel with those they’ve previously been socializing with.
Sand tiger sharks are not particularly aggressive and are generally considered harmless to humans. Despite that, some experts believe they may be responsible for a spate of attacks off the coast of Long Island this year.
Over the peak summer period, there were five shark attacks in just two weeks. Florida Program for Shark Research Program Director Gavin Naylor believes sand tiger sharks were likely to blame.
According to him, there are lots of sand tiger sharks off the coast of Long Island, but they don’t usually present a problem. However, this year, much of the baitfish moved closer to shore, bringing the sharks with them.
Naylor is quick to point out that “sharks don’t target people. If they did, we’d have about 10,000 bites a day.”
The juvenile sand tigers are really after fish – they just mistake hands and feet for prey, resulting in the attacks.
None of the attacks off Long Island were fatal, nor were the victims seriously injured.
What do Sand Tiger Sharks Eat?
Sand tiger sharks might be cannibalistic in the uterus, but they don’t eat each other once they’re born.
For the most part, sand tiger sharks eat teleosts and other bony fish, such as hake, herring, wrasses, and snappers.
They also feed on rays, and other small sharks, with one study showing that elasmobranchs make up approximately 42% of their diet.
Sand tiger sharks are voracious predators that usually feed alone and at night. They do sometimes hunt cooperatively, “systematically surrounding and concentrating schooling prey before feeding.”
During such collective hunting sessions, the sand tiger sharks use their tails “to generate sharp underwater pressure waves” that either herd or disorient the fish, making them easier to catch.
Even though they appear to move quite slowly most of the time, they’re capable of bursts of speed that enable them to catch and consume fast-swimming fish like tuna.
In addition to fish, sand tiger sharks also prey on crabs, lobsters, and squid.
Like many shark species, the sand tiger doesn’t require a huge amount of food, with studies indicating that they only consume around 2% of their body weight each week. Their food intake also varies seasonally, dropping by approximately 25% in winter.
Sand tiger sharks use the electroreceptors on their snouts to locate bottom-dwelling prey and to detect potential victims in murky waters.
What Hunts Sand Tiger Sharks?
Adult sand tiger sharks have no natural predators and little to fear, but the same can’t be said for juveniles.
They are vulnerable to predation by several larger shark species, including the bull shark and the great white. It’s also possible that Shortfin Makos and tiger sharks prey on them.
As with most shark species, the greatest threat to their existence comes from us humans. Sand tiger sharks are vulnerable to extinction, due to the combined effect of overfishing and their low reproductive rate.
Between 1980 and 1990, the global population of sand tiger sharks “experienced a 75 percent decline” due to “being caught commercially and as bycatch in bottom trawls and gillnets.”
Some commercial fisheries target the sand tiger shark for its fins, meat, and oil. They are also caught for the aquarium trade due to their ability to survive in captivity.
Conclusion
Sand tiger sharks might look terrifying with their protruding teeth, but they’re generally harmless, showing aggression only when provoked.
They are an unusual shark species as they are the only ones to use air to maintain buoyancy instead of relying on their oily livers. They are also the only species to practice intrauterine cannibalism.
This practice means they have one of the lowest reproductive rates of any shark species, with each female producing just two pups per litter.
This characteristic, combined with pressure from the commercial fishing industry, means the sand tiger shark is now fighting for its survival.
Unless we end the shark fin trade and do more to prevent the overfishing of this species, it could disappear from our oceans before we have a chance to truly understand its curious adaptations.
Nicky is a British adventurer and animal lover who spends her time exploring the natural world and writing about her experiences. Whether on horseback, underwater, running, hiking or just standing with a fishing rod in hand, she embraces everything her adopted home of South Africa has to offer.