43 Fun Facts About Hammerhead Shark

What is the scientific name for the hammerhead shark family?

Sphyrnidae, from the Greek sphyrna, 'hammer', is the hammerhead family; the similar-looking Sphyraenidae are the barracudas.

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

The cephalofoil is the flattened, sideways-extended head; the eyes sit at its tips, and the mouth lies underneath near the middle.

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

The winghead shark (Eusphyra blochii) has its own genus, Eusphyra, and proportionally the largest hammer of all, while every other hammerhead sits in Sphyrna.

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

Half: the Eusphyra species' hammer can be as wide as half its total length; it grows to about 1.9 m, so the hammer can span nearly a metre.

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

360 degrees: with eyes at the tips of the hammer, a 2009 study found hammerheads can see above and below themselves at all times, with better binocular vision than pointy-nosed sharks.

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

Like a larger radio antenna: spreading the ampullae of Lorenzini, pores that sense the electric fields of living animals, across the wide head lets the shark sweep a bigger area for prey.

Which are the hammerheads' closest relatives?

The requiem sharks (family Carcharhinidae), which include the bull, tiger and blue sharks; molecular studies place the hammerheads as their close relatives or even within them.

Which hammerhead species has the scientific name Sphyrna zygaena?

The smooth hammerhead is Sphyrna zygaena; it lacks the central notch on the front of its head that the scalloped hammerhead has, and ranges into cooler temperate seas.

What is the smallest hammerhead species?

The bonnethead (Sphyrna tiburo) is the smallest, topping out around 1.5 m and 11 kg; it is the hammerhead most often kept in public aquariums.

How much did the 4.4 m great hammerhead caught off Boca Grande, Florida, in 2006 weigh?

580 kg: the Boca Grande female, landed in May 2006, measured 4.4 m and was carrying 55 pups, the largest litter recorded for the species.

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?

Stingrays are the great hammerhead's favourite prey; it sweeps its head over the sand to sense rays buried there, and venomous barbs lodged in its mouth do not seem to trouble it.

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

It knocks the ray down and pins it to the seabed with its head, then pivots to bite off each pectoral fin, crippling the ray before tearing it apart with head shakes.

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

96: one great hammerhead caught off Florida had 96 stingray spines lodged in and around its mouth, and the venomous barbs did not seem to bother it.

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

Swimming on their side: a 2016 study of tagged great hammerheads found 'rolled swimming' up to 90% of the time, using the tall dorsal fin as a lift surface and cutting 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?

11 months: great hammerheads breed every two years after an 11-month gestation, producing litters of 6 to 55 pups, typically 20 to 40, each 50 to 70 cm long.

What is the typical litter size for most hammerhead species?

12 to 15 pups is the usual litter for most hammerheads; the great hammerhead is the exception with 20 to 40, and the pups, given no parental care, huddle together in warm 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?

Reproduce asexually: a female at Nebraska's Henry Doorly Zoo gave birth in 2001 with no male present, and a 2007 DNA study found only maternal genes, proving automictic parthenogenesis.

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

Seagrass: some of the smallest hammerheads have stomachs more than half full of seagrass, which they can partly digest, making the species the first shark shown to be omnivorous.

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

The shape of its head: adult males develop a distinct bulge along the front of the cephalofoil that females lack, the only known sexual dimorphism in shark head shape.

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

The whale shark: a 2022 study of tissue samples from Ningaloo Reef showed whale sharks digest and assimilate algae from sargassum, making the biggest fish an omnivore too.

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?

Golfo Dulce, a tropical fjord on Costa Rica's Pacific coast; tagged scalloped hammerheads travel between Cocos Island and its mangrove nurseries, where juveniles shelter from predators.

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

The US Endangered Species Act: in 2014 NOAA listed four populations of scalloped hammerhead, making it the first shark species protected under the Act.

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

Critically Endangered: the IUCN's 2019 assessment found steep declines driven by the fin trade, and the species' low abundance and long generation time make recovery slow.

By 2013, how many unprovoked hammerhead attacks were recorded since 1580, and how many deaths?

17, with no deaths: the International Shark Attack File had logged 17 unprovoked hammerhead attacks since 1580 and no fatalities; most species are too small to hurt a person seriously.

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

Hong Kong handles roughly half of the world's shark fin trade, making it the largest market; traders prize hammerhead fins for their abundant 'fin needles' (ceratotrichia).

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

6,313 metric tons: reported hammerhead catches rose from 75 tons in 1990 to 6,313 tons in 2010, and their habit of aggregating in schools makes them easy targets for commercial fleets.

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

CITES: at its March 2013 meeting in Bangkok the convention listed the scalloped, great and smooth hammerheads on Appendix II, requiring permits for international trade in their fins and meat.

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

Fewer than 15: scalloped hammerheads are hard to keep, bumping their heads on tank walls and faring badly in transport, so only a handful of institutions had managed to display them.

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

Beizam: the hammerhead is a family totem for Torres Strait Islanders, appears on the dhari headdresses worn in ceremonial dances, and is linked with law and order.

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

A respected aumakua: Hawaiians regard the hammerhead as a family guardian rather than a man-eater; children born under its sign are said to become warriors and sailors, while great whites, tigers and bulls are the dreaded niuhi.

What is the Hawaiian name for the hammerhead?

Mano kihikihi is the Hawaiian name, 'kihikihi' meaning angular or zigzag; Maui families take a passing hammerhead as a sign the gods are watching and the ocean is in balance.

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

Sphyrna tudes: Valenciennes coined Zygaena tudes in 1822 and it was long applied to the great hammerhead, until Enrico Tortonese showed in 1950 that his specimens were smalleye hammerheads.

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

Theodore Gill, the American ichthyologist, erected the genus Eusphyra, meaning 'true hammer', in 1862 for the species with proportionally the largest head.

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

To protect the stomach from spiny blue crab shells, their main prey, is one hypothesis for the plant material; a 2018 study with carbon-labelled plants showed the sharks also digest and absorb it.

What is the typical lifespan of a great hammerhead?

20 to 30 years is the usual lifespan; the record Boca Grande female of 2006 was estimated at 40 to 50 years old, far beyond the norm.

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

Its vertebrae: the unusual structure of the hammerhead's vertebral column is what lets it make its sharp turns; the head shifts during turns and provides lift.

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.