Thresher sharks are big, powerful, and very fast, but they aren’t species we should necessarily fear. Although they’re certainly large enough to hurt us, they generally appear too timid to try.
There’s only been one recorded attack by a thresher shark, and that occurred after someone had grabbed its tail. Given that its tail is its secret weapon, I’m not surprised it got angry!
Most sharks are only dangerous at one end, but the thresher shark’s tail is just as deadly as its bite.
This article will reveal how thresher sharks use their tails as deadly weapons, what they eat, where they live, and why you shouldn’t be afraid of them.
What do Thresher Sharks Look Like?
Thresher sharks are among the easiest to identify, with their elongated tails and torpedo-shaped bodies.
There are three species of thresher sharks, all of which have characteristically long tails that set them apart from all other sharks.
The upper lobe of the thresher shark’s caudal fin can be nearly as long as the rest of its body, sometimes reaching over nine feet in length.
Thresher sharks also have large pectoral fins and sleek, aerodynamic bodies. Their backs are usually grey or brown but can also be blue or black, while their undersides are white.
All thresher sharks have large eyes adapted for hunting in low light, but the big-eye thresher shark is the only one whose eyes are so large that they extend onto the top of its head.
Thresher Shark Taxonomy
Aristotle first named the thresher shark the fox shark, because of its intelligence and cunning, and its scientific name, Alopiidae vulpine, still reflects this.
Although all three species of thresher shark belong to the Lamniformes order, making them mackerel sharks, they lack many “obvious mackerel shark characteristics,” such as an equal-lobed tail and large jaws.
The three species of thresher shark, common, big-eye, and pelagic, are the only sharks in the Aplopiidae family and share certain characteristics, the most notable being the long upper lobe of the caudal fin.
A fourth species of thresher shark may exist, but the only evidence we have are “muscle samples from one specimen.”
The thresher shark lineage first appeared around 55 million years ago, which is quite recent for a shark, with some species dating back over 100 million years.
Thresher Shark Characteristics
The thresher shark’s long, powerful tail propels it through the water at an astonishing speed, and can easily reach 30 mph (48 kph), making it one of the fastest sharks in the ocean.
In addition to the long tail, thresher sharks have endothermic capabilities that “make them agile hunters and quick swimmers.”
They can retain metabolic heat by using a blood vessel countercurrent exchange system, warming their bodies to around 3.6°F (2°C) higher than the sea around them.
Thresher sharks are such fast and powerful swimmers that they can propel themselves out of the water, producing breath-taking aerial displays like the one witnessed off the UK coast a couple of months ago.
Only a few sharks breach and scientists are still unsure of the reason for this behavior. The thresher shark may be traveling so fast when pursuing prey that it bursts out of the water before it can stop itself. Alternatively, it could be a form of courtship or a way to remove irritating parasites.
Not only are thresher sharks fast but they’re also big, ranging between 10 to 20 feet.
The common thresher shark is the largest of the three species, averaging between 14 and 19 feet long. The big-eye thresher isn’t far behind at 11 to 13 feet, while the pelagic thresher is the smallest, measuring approximately 10 feet in length.
Thresher Shark’s Life Cycle
Like most sharks, thresher sharks reproduce via internal fertilization, but it takes a while for them to get to that stage. Male thresher sharks only reach sexual maturity at around seven years old, while females take even longer.
One study concluded that female thresher sharks are sexually mature only at 13.2 years old.
In the northwest Atlantic Ocean, common thresher sharks mate in late summer, while in other parts of the world, they breed all year round.
After fertilization, the embryos hatch inside the female’s body. They then remain there for some months, initially feeding off their own yolk sac before moving on to the other unfertilized eggs in the womb.
This form of nutrition is a type of intrauterine cannibalism but isn’t quite as barbaric as that performed by the sand tiger shark. Thresher shark embryos practice oophagy, meaning they eat eggs in the uterus, while the sand tiger preys on its siblings.
After a nine-month gestation period, the thresher shark gives birth to a small litter of two to six pups. At birth, the pups are already quite large, measuring around five feet long.
As juveniles, they grow rapidly, getting approximately 1.6 feet longer each year. This growth spurt soon slows, and the average annual growth of adults is just “0.3 feet (10 cm) a year.”
Scientists aren’t sure of the thresher shark’s life span, but estimate it to be between 19 and 50 years.
Where do Thresher Sharks Live?
Thresher sharks inhabit tropical and temperate waters across the world. These highly migratory sharks can be found in both coastal waters and open ocean, although the common thresher is “most common near land.”
The pelagic thresher shark is more limited in its distribution, only occurring in the Indian and Pacific Oceans.
Juvenile thresher sharks utilize near-shore waters more frequently than adults and can often be found in coastal bays.
Adult thresher sharks prefer the open ocean, although common thresher sharks will also move toward the coastline in search of food.
Although thresher sharks are sometimes seen close to the surface, scientists believe they spend most of their lives in deep waters around 1,800 feet.
Thresher sharks migrate seasonally, sometimes traveling across entire ocean basins. As a result, they are commonly seen outside their normal range, although they prefer warmer waters ranging between 53 and 65 °F.
Thresher Shark Behavior
Thresher sharks have a secret weapon, and it’s not their teeth. With tails that are almost half as long as their bodies, thresher sharks bull whip their victims into submission.
The unique hunting strategy of the thresher shark sets it apart from all other shark species.
Instead of grabbing its prey with its mouth, the thresher shark accelerates towards a shoal of fish, using its large pectoral fins to screech to a halt as it bursts into its target. As it stops, it ducks its snout down and slings its tail over the top of its head.
According to researchers at the Thresher Shark Research and Conservation Project at the University of Liverpool, thresher sharks can unleash their deadly tails at speeds of up to 80 mph (approximately 128 kph).
When the tail strikes, it causes instant chaos, leaving small schooling fish in tatters. Dazed and confused, or even physically injured, the fish can do little more than float in the water and wait for their inevitable demise.
Scientists suspect that the thresher shark’s tail travels so fast that it creates a shockwave “that’s strong enough to debilitate small prey.”
After the strike, the thresher shark leisurely swims back through the fish, feeding on its dazed and injured victims.
Thresher sharks are most active at night but will hunt during the day if an opportunity presents itself.
They are extremely aggressive predators but surprisingly timid around humans. They’re not particularly friendly towards others of their own species either, living a largely solitary existence.
What do Thresher Sharks Eat?
The thresher shark’s whip-like tail makes it a formidable predator and specializes in hunting small pelagic fish like sardines, anchovies, mackerel, and hake.
The big-eye thresher has a more diverse palate, incorporating benthic, or bottom-feeding fish, into its diet. It also feeds on various crustaceans, as well as squid.
Studies suggest that pelagic thresher sharks also have a taste for squid, with one article highlighting the presence of both Humboldt and purple-back flying squid in the stomachs of pelagic threshers off the coast of Ecuador.
Other studies show that the common thresher shark’s diet changes as it moves from a cold-water to a warm-water period.
During the cool-water period, it focuses on squid, while in a warm-water habitat, it enjoys a more varied diet that incorporates anchovies, sardines, hake, and haddock.
The pelagic red crab is also relatively common during those warm-water periods but is absent from the sharks’ cold-water menu.
What Hunts Thresher Sharks?
Orcas have established themselves as the ocean’s apex predators. Not only will they take on blue whales and great whites, but they’ve also been seen hunting both common and pelagic thresher sharks.
It’s also believed that great whites might predate thresher sharks, but these are the only predators big and brave enough to take them on.
Humans present a far greater threat to all three species of thresher shark, hunting them for their meat, fins, and oil.
According to NOAA fisheries, “US wild-caught Atlantic common thresher shark is a smart seafood choice because it is sustainably managed and responsibly harvested.” Despite that, the common thresher is considered to be “highly vulnerable to overfishing worldwide.”
The IUCN lists all three thresher shark species as vulnerable to extinction. That’s mainly because, in addition to being targeted by commercial fishing operations, they are also popular sport fish and have a low reproductive rate, which makes it difficult for the population to recover.
Thresher sharks are unusual sharks with a unique hunting technique that sets them apart from all other species.
Instead of relying on powerful jaws and sharp teeth to make their kill, thresher sharks have turned their tails into weapons of mass destruction.
Although thresher sharks are fierce predators, they rarely act aggressively toward humans. Thresher sharks are shy and timid around humans, moving away swiftly when approached.
Thresher sharks are slow to mature and only give birth to small litters, which makes them vulnerable to overfishing. It takes so long for the population to recover that all three species are “at risk in many regions due to demand for their valuable meat and fins.”
As tasty as the thresher shark may be, I’d still rather see it swimming in our oceans than listed on a menu. How about you?
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.