Meet the Thresher Shark
Neptune's Note VIII
Name: For all of the grumbling I’ve done over the terrible names given to many species of whales, dolphins and porpoises, the sharks, it seems, have avoided this issue entirely. Instead, they swim along happily, in the knowledge that their names are logical and often endearing. As is the case for the thresher shark, named so for its thresher-like tail. Threshing is a farming method whereby seed crops are beaten from their straw in a striking motion, a motion used by the thresher shark when hunting. And so one can’t deny, the name makes sense.
Family: Alopiidae Bonaparte. Yes, the naturalist who coined the term for the thresher’s family name and genus was the nephew of that small man — Napoleon Bonaparte. ‘Alopiidae’ and alopias (genus) both come from the ancient Greek word, alṓpēx, meaning fox and so all three extant species of the thresher shark are commonly known as fox sharks in other languages. The three extant species include the common thresher, the bigeye and pelagic.
Order: Lamniformes1 are an order of sharks otherwise known as mackerel sharks, species include the infamous great white and more obscure members such as the megamouth shark or the goblin shark.
Location: Thresher sharks can be found in all temperature waters around the world and prefer an ocean depth of 500 metres or less, making them a pelagic species. Though they aren’t considered a deep-sea shark, they have occasionally been spotted in even deeper waters than this in recent years. Bigeye threshers have been recorded in new territories, suggesting environmental factors are forcing them to move further afield.
Population: As a primarily pelagic species they can be hard to pin down so no global population estimate has ever been made.
Status: All three thresher shark species are listed as vulnerable on the IUCN Red List due to the multiple threats they face.
Weight: Up to 500 kg for a common thresher - the heaviest and longest of the species by far.
Length: Up to 6 metres for the common thresher, with the bigeye thresher measuring 3 metres at most and the pelagic being the smallest.
Lifespan: A thresher can live anywhere between 19 and 50 years.
Anatomy: Immediately identifiable by the upper lobe of their tail, which can be as long as their bodies, all thresher sharks have a cone-shaped nose and a small downturned mouth. This combination gives one the impression that they’re mildly concerned at all times. They’re a fairly slender animal with a small dorsal fin but quite large pectoral fins. Specific features like their streamlined shape2 make them fast swimmers and their dark backs but light bellies help them to blend with the water, contributing to their place at the top of the food chain. There are several ways to tell the three thresher species apart — primarily from their size and their colouring. It’s worth noting that as someone with a ridiculous, misplaced fear of sharks, the thresher was an easy one to research because they’re just so damn cute!
Diet: Thresher sharks possess a remarkable hunting technique, using their elongated tails not just for swatting or stunning their prey but to strike it so accurately that they slice it in half before eating. This must be one of the most efficient hunting methods in the entire ocean. With a preference for pelagic fish like bluefish, mackerel and juvenile tuna, their diet can also be quite varied and occasionally includes squid, cuttlefish, crustaceans and even seabirds on the menu.
Social habits: Keeping themselves to themselves, thresher sharks take their solitude very seriously and, in the Indian Ocean at least, have been known to separate themselves by depth and space depending on their sex. There are, however, contradictory tales of threshers hunting in groups of two or three on occasion as well. Despite being a skillful, intelligent and versatile apex predator, the thresher shark is not a danger to humans. They are a very shy species of shark and though they are typically non-aggressive, as a wild animal, feeling threatened or cornered may provoke them.
Reproduction: Breeding throughout the year within no specific season, threshers are also ovoviviparous, meaning the egg hatches inside the body and they give birth to live, fully developed young. The gestation period lasts around 9 months and produces around 2-4 pups in the litter.
Unique facts:
There are very few shark species that are able to breach but the thresher shark is one of those few. Using the power of their lengthy tail to burst from the surface and twirl through the air, like most animals who express this behaviour, it’s most likely the best way to rid themselves of any parasites, to communicate, or simply for a bit of fun.
At least two of the three thresher shark species have evolved endothermic capabilities allowing them to retain metabolic heat. This means they can keep their body temperature above the temperature of the water around them, helping them to thrive in the freezing open ocean.3
Threats they face: Thresher sharks are especially vulnerable to overfishing due to their low fecundity, making them a species at high risk of population decline. Targeted for commercial purposes, their meat, liver oil, skin and fins are harvested for various products, including delicacies like shark fin soup, leather goods, and vitamin supplements. The common thresher shark, in particular, has suffered significantly from intense fishing practices as they continue to be directly targeted while also suffering as bycatch across the world’s oceans. Unfortunately, thresher sharks are also valued in sport fishing and are considered one of the strongest fighting sharks along with the shortfin mako. Their strength and power makes them an entertaining catch for the pursuing anglers who must find their agony amusing.
A ban on trophy hunting of any shark is needed. So too a ban on shark finning.. This, alongside stricter bycatch laws is necessary to see an increase in thresher shark population. As a pelagic species, the ratification of the High Seas Treaty would also massively benefit this species and see the vast ocean that they call home better protected against illegal shark finning, pollution, and overfishing
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Amie 🐋
From the ancient Greek word, lamia, meaning a kind of shark.
They can swim at speeds of up to 20 mph.
It comes from a strip of muscle along each flank which has a more compact network of blood vessels working to transfer metabolic heat inwards to the shark’s core.