Big Eye Thresher
The largest of the thresher sharks
Common Name– Mackrel Sharks
* There are possible undiscovered species of Thresher sharks. So far, scientists recognize three extant species of Thresher Shark: The Pelagic Thresher, Bigeye Thresher, and the Common Thresher. A species of Thresher Shark was found of the coast of Baja in 1995. After scientific analysis of its DNA, it was found to potentially be a new species of Thresher Shark. These has only been one sample of this potential species found so far.
Status: IUCN Red List Vulnerable
Average Size and Length: The Bigeye Thresher is the largest of the three species of Thresher sharks. Up to 18 feet. Some accounts of the largest of the three species, the Bigeye Thresher reaching 20 feet in length. The largest ever caught and recorded was 32 feet in length. It was caught by a fisherman named Roger Nowell off the coast of Lands End and sadly didn’t live and was auctioned off. See the story here.
Average Weight: 900 pounds
Current Rare Mythical Sightings: The fox of the ocean. These sharks have a place in history, and were actually named after foxes! The first person to ever write about Thresher Sharks was Aristotle in the book Historia Animalia. In the book, Aristotle claims that Thresher Sharks are able to bite through fishing lines to escape and will temporarily swallow their young to protect them from predators. Both of these behaviors, which are scientifically erroneous, lead Aristotle to praise the high level of intelligence and cunning characteristics of the Thresher Shark, ultimately leading to the name “Alopex.” In Greek, Alopex means fox, which are considered highly intelligent and cunning animals.
There’s a long-standing myth that Thresher Sharks and Swordfish work together to attack whales. The myth says that the Thresher Shark will swim in front of a Whale and district it by violently whipping its tail around, meanwhile the Swordfish will attack the Whale with its sharp nose, piercing it. Then they share the spoils. This cannot be true since neither are able to eat whale. Both predate and do not scavenge.
Teeth and Jaw: The teeth of a Thresher shark are, small, curved and smooth-edged and extremely sharp. They are much more triangular and pointier in the Common and Bigeye rather than the Pelagic.
Sexual dimorphism. For example, the teeth of Bigeye Thresher shark (Alopias superciliosus) females are broader than those of males.
Dermal Denticles: Bigeye Threshers have large and small dermal denticles, with the smaller denticles intermingled among the larger ones. The smaller denticles, which make up the greater percentage, are very widely spaced, shaped like a lance head (tapering to a point at the apex) and are spinous rather than scale-like.
Head: The snout is short, and the head is small flat top.
Tail: The Thresher shark is known for its long upper lobe of the tail. It is about as long as the rest of the shark. It is used primarily to herd fish together and, like a whip, slapping through the water at prey stunning it. It is thick-skinned and leathery.
Demographic, Distribution, Habitat, Environment and Range: Thresher sharks preferably live in open ocean but will come inshore to hunt prey. They will inhabit the surface down to 1300+ feet. These sharks may go deeper than the other two species but stay around 330 feet. They can be found worldwide in cold to temperate to warmer water seas. They are less common in warm regions. They migrate to higher latitudes in summer for breeding and return in autumn. Bigeye Threshers stay in a bit warmer waters than the Common Thresher.
Diet: Mainly schooling fish so they can herd and stun them with their whipping tails. They are known to predate on bluefish, mackerel, herring, lancets and others. They also may feed on squid, octopus and even crustaceans. Thy may also occasionally stun seabirds and prey on them.
Ram-Suction Index: Ram. After prey is stunned they will lunge and bite until it is completely consumed.
Aesthetic Identification: Thresher sharks are bluish grey or shiny brown on the top side of the shark, the sides are a coppery silvery shimmer, and pale white under and belly side of the shark. This does not extend in a patch along the pectoral fins. Again, an example of counter-shading. There is a white dot, or white splotches on the tips of the narrow pointed pectoral fins and pelvic fins.
The most well-known identifier of this shark is its long tail. The upper lobe of the tail is about as long as the whole shark. It has a slight triangular notch on the upper tip, and the upper lobe is triangular in shape pointing downward. It also has a downward facing triangle at the base. Labial furrows are present, and it has fairly large eyes on the sides of its head and almost extend onto the flat-top head. These eyes are used to see in the darkest depths of the ocean.
They have deep, horizontal grooves above the gills.
Biology and Reproduction: Thresher sharks are endothermic and are warm-blooded. They have extra red muscle and are built for speed and power underwater. They have slow-oxidative muscles combined with blood vessel countercurrent exchange which helps them regulate their blood pressure internally. This leads them to have blood that is 3.6°F (2°C) warmer than the surrounding waters. Being warm blooded allows them to stabilize proteins in cooler waters and helps them more efficiently use their muscles.
Male Thresher sharks reach sexual maturity at 9 feet and females at 10 feet. They mate during the summer. Thresher sharks are ovoviviparous, and gestation is between 8-10 months. Thresher sharks engage in intrauterine cannibalism (within the uterus). Therefore post, they will have 4-6 young that average from 4 to 5 feet long. This species is born 110-140 cm long.
Thresher sharks are documented to live between 20 and 50 years. The average is 22 years.
Sensing and Intelligence: Like all sharks, Thresher sharks rely heavily on sensing electrical currents through their Ampullae of lorenzini and their lateral lines.
The Thresher shark as very large, distinct eyes. They have adaptive vision to see prey in the vast darkness of the open ocean, but its vision is poor. “Oh my, what large eyes you have! Better to see you with!” Bigeye Thresher sharks do not have a cone, so they cannot see color.
Thresher sharks may come together cooperatively in twos or more and work together by herding and stunning prey with their tails.
Breaching: Thresher sharks have been documented and are known to breach or leap out of the water.
Speed: Thresher sharks are agile and quick. Thresher sharks reach some of the fastest speeds in the shark world. Thresher sharks reach speeds and bursts up to 30mph. They are torpedo-shaped, reducing drag. They have a strip of aerobic red muscle along its flanks that helps give it extra strength and power.
Thresher Sharks Future and Conservation:
Thresher Shark Recorded Attacks on Humans: There has only be one documented Thresher Shark attack on a person and it was provoked by the individual grabbing the Thresher Shark’s tail. There have been four accounts of Thresher Sharks attacking boats, but were individuals fighting against capture. Thresher sharks are not a threat to humans.