50 Fun Facts About Hammerhead Shark

What is the scientific name for the hammerhead shark family?

Sphyrna is Greek for hammer; Sphyraenidae, confusingly, are the barracudas.

What is the technical name for the hammerhead's flattened, T-shaped head?

The eyes sit at each end and the small mouth directly underneath in the middle.

Which hammerhead is the only species not placed in the genus Sphyrna?

It has its own genus, Eusphyra, and proportionally the largest hammer of all.

How wide can the hammer of the Eusphyra species be, as a fraction of its body length?

The species reaches only about 1.9 m long, so the hammer can span nearly a metre.

How many living hammerhead species are there?

They range from the 6 m great hammerhead to the 1.5 m bonnethead.

What field of vision does the eye placement on the hammer give in the vertical plane?

They can see above and below at all times, plus better binocular vision and depth perception.

Spreading electroreceptors across the wide head lets a hammerhead sweep for prey like what?

The pores are the ampullae of Lorenzini, which detect the electric fields of living animals.

Which are the hammerheads' closest relatives?

That family, the Carcharhinidae, includes bull, tiger and blue sharks.

Definitive hammerhead fossils date back to which epoch?

Older DNA studies had put the family's origin in the Miocene, about 20 million years ago.

What is the largest hammerhead species?

It averages about 4 m and 230 kg; the longest on record was 6.1 m.

What is the smallest hammerhead species?

It tops out around 1.5 m and 11 kg, and is the hammerhead most often seen in public aquariums.

The heaviest known great hammerhead, caught off Boca Grande, Florida, in 2006, weighed how much?

She was 4.4 m long and estimated at 40-50 years old, twice the typical lifespan.

How can you tell a great hammerhead's head from a scalloped hammerhead's?

The smooth hammerhead has a rounded head with no notch at all.

What is the great hammerhead's favourite prey?

One Florida specimen had 96 stingray spines lodged in and around its mouth and seemed untroubled.

How does a great hammerhead use its head when attacking a stingray?

It then pivots to bite each pectoral fin, crippling the ray before sawing it apart with head shakes.

How many stingray spines were found in and around the mouth of one great hammerhead caught off Florida?

The venomous barbs do not seem to bother the shark.

A 2016 study found great hammerheads spend up to 90% of their time doing what to save energy?

'Rolled swimming' uses the tall dorsal fin for lift and cuts drag by about 10%.

Unlike most sharks, where have great hammerheads been observed mating?

A Bahamas pair spiralled upward around each other and mated on reaching the surface.

How long is a great hammerhead's gestation?

Females breed every two years; litters run 6-55 pups, typically 20-40, each 50-70 cm long.

What is the typical litter size for most hammerhead species?

The great hammerhead is the exception with 20 to 40; pups get no parental care and huddle together in warmer water.

How do hammerhead embryos get nourishment in the later stages of gestation?

The depleted yolk sac transforms into a structure like a mammalian placenta.

How does a male hammerhead typically persuade a female to mate?

Reproduction happens only once a year.

In 2007, the smallest hammerhead became the first shark known to do what?

A female at Nebraska's Henry Doorly Zoo produced a pup by automictic parthenogenesis, a perfect DNA match to its mother.

What surprising food makes up as much as half the stomach contents of some of the smallest hammerheads?

They can partially digest it, making the bonnethead the first shark shown to be omnivorous.

The smallest hammerhead is the only shark known to show sexual dimorphism in what?

It is also called the shovelhead for its spade-like cephalofoil.

Which other species was later found to be omnivorous, after the smallest hammerhead?

For a while the bonnethead was the only known case.

What unusual social behaviour do some hammerheads show by day?

Scalloped hammerheads gather in schools of hundreds, then split up to hunt alone at night.

Tagged scalloped hammerheads migrate between Cocos Island and mangroves in which Costa Rican fjord?

Juveniles thrive in shallow bays and mangroves that shelter them from predators.

The scalloped hammerhead was the first shark protected under which law?

It has been Critically Endangered on the IUCN Red List since 2019.

How does the IUCN classify the great hammerhead as of 2019?

Its large fins are prized for shark fin soup, and its low abundance and long generation time make it hard to recover.

How many unprovoked hammerhead attacks on humans are documented since 1580, and how many deaths?

Most species are simply too small to hurt a person seriously.

Roughly how many great hammerheads are estimated to be traded for their fins each year?

That is about 21,000 tonnes of shark; the meat is generally unwanted and the bodies discarded.

Which city is the world's largest shark fin trade market?

Traders say hammerheads have some of the best 'fin needles'.

Recorded hammerhead catches rose from 75 metric tons in 1990 to how many metric tons by 2010?

Their habit of aggregating makes them easy targets for commercial fleets.

Hammerheads were added to Appendix II of which convention in March 2013?

That brought their fishing and trade under licensing.

As of 2014, how many public aquariums worldwide kept scalloped hammerheads?

They are hard to keep: they bash their heads on tank walls and are especially vulnerable in transit.

What is the hammerhead called by Torres Strait Islanders, who use it as a family totem?

It features on the elaborate dhari headdresses worn in ceremonial dances and is linked with law and order.

In native Hawaiian belief, the hammerhead is which kind of shark?

Children born under its sign are said to become warriors and sailors; great whites, tigers and bulls are the niuhi.

What is the Hawaiian name for the hammerhead?

Maui natives see a passing hammerhead as a sign the gods are watching and the ocean is balanced.

The dried remains of hammerheads may have inspired the legend of which headless monster?

Blemmyes were said to have faces in their chests.

What does the great hammerhead's species name 'mokarran' mean in Arabic?

Eduard Rüppell described it as Zygaena mokarran in 1837.

For many years the great hammerhead was wrongly known by which scientific name, coined in 1822?

Enrico Tortonese found in 1950 that Valenciennes's illustrated specimens were actually smalleye hammerheads.

Who placed the species with the biggest hammer in its own genus Eusphyra in 1862?

The name means 'true hammer'; it was ignored until Bigelow and Schroeder revived it in 1948.

Why might the smallest hammerheads swallow marine plants, according to one hypothesis?

A 2018 study with carbon-labelled seagrass showed they really digest and absorb it.

What is the typical lifespan of a great hammerhead?

The record Boca Grande female was thought to be 40-50.

Which structure, rather than the head shape, is most instrumental in hammerhead sharp turns?

The head still shifts and provides lift.

Where does the great hammerhead rank as a threat to divers?

Its size makes it potentially dangerous, but attacks are rare.

According to National Geographic, what do hammerheads do in summer?

They favour warm tropical coasts and continental shelves the rest of the year.

Compared with other sharks, hammerhead mouths are what?

The small crescent mouth sits under the head, ideal for grabbing rays and flatfish off the bottom.

Roughly how heavy was the record hammerhead specimen caught off the Florida coast in 1906?

The 1906 Florida specimen weighed more than 680 kg (1,500 lb), well above the great hammerhead's 230 kg average.