Hammerhead sharks are most common near Wolf Island and Darwin Islands in the north of the archipelago. Galapagos is one of the last remaining places where large schools of scalloped hammerhead sharks can be observed. They can be observed cruising over reefs and boulder-strewn slopes.
There are 10 known species of Hammerhead sharks (9 by some accounts) that range from 0.9 to 6 metres (3 to 20 feet) in length. Of these species, 9 belong to the genus ‘Sphyma‘, and 1 to the genus ‘Eusphyra‘. Together these genera belong to the family ‘Sphyrnidae‘, which itself belongs to the order ‘Carcharhiniformes‘. This is the largest order of sharks, with over 270 species in total, including the families of tiger sharks and requiem sharks.
Hammerhead Shark Appearance And Characteristics
All the species of Hammerhead Shark have a projection on each side of the head known as a cephalofoil. This feature makes the sharks head appear like a ‘flattened hammer’, hence the name ‘hammerhead shark’. The sharks eyes and nostrils are at the tips of their hammer shaped heads.
Hammerhead sharks are silver-grey to grey-brown in color with white undersides.
Like all sharks, the Hammerhead sharks have electrolocation (use of electrical impulses) sensory pores called ‘ampullae of Lorenzini’ (special sensing organs, forming a network of jelly-filled canals found on cartilaginous fishes). By distributing the receptors over a wider area, hammerheads can sweep for prey more effectively. These sharks have been able to detect an electrical signal of half a billionth of a volt.
The hammer-shaped head also gives these sharks larger nasal tracts, increasing the chance of finding a particle in the water by at least 10 times as against the ability of other ‘classical’ sharks. It is suggested that hammerheads are among the most highly evolved shark species.
Another characteristic is that they are known for their schooling behaviour, often found in groups of several hundred.
Habitat And Location
The Galapagos Islands are a significant habitat for hammerhead sharks, recognized for having the largest biomass of sharks in the world. The islands of Darwin and Wolf in the far north-west of the archipelago are particularly notable locations where large schools of hammerhead sharks are observed.
They can however, be found in tropical and temperate waters all around the world. From the tips of South America and Australia, to the coastlines of Europe, North America and the UK. Most species love coastal waters with plenty of prey, and some also like waters over the continental shelf.
You won’t find them in the most northern latitudes in the Arctic Circle, or around Scandinavia, the Baltic, Canada or Alaska.
Hammerhead sharks are aggressive predators, eating fish like sardines, herring, or mackerel. They also hunt for rays, cephalopods and crustaceans.
Hammerhead sharks have rather small mouths and seem to do a lot of hunting at the bottom of the ocean. They are also known to form schools during the day, sometimes in groups of over 100. In the evening, like other sharks, they become solitary hunters.
Reproduction And Lifespan
Reproduction in the hammerhead shark occurs once a year with each litter containing 20 to 40 pups – the average is around 26. Hammerhead sharks are quite aggressive in courtship. The male will bite the female until she submits, allowing mating to occur. Unlike many other shark species, the hammerhead shark has internal fertilization which creates a safe environment for the sperm to unite with the egg.
The embryo develops within the female inside a placenta and is fed through an umbilical cord, similar to mammals. The gestation period is 10 to 12 months. Once the pups are born the parents do not stay with them and they are left to fend for themselves.
Young hammerheads are left in nurseries in shallow coastal waters like flooded mangrove forests, where they grow for one to two years before venturing into the open ocean.
Across the various species, the lifespan of Hammerhead Sharks ranges between 20 – 30 years in the wild, and a similar age in captivity. The oldest on record was estimated to be closer to 40 years old but that range of longevity is exceptional.
Hammerhead Shark Predators
The Great Hammerhead Shark is an apex predator, and as such there are not many other marine animals that they have to worry about, at least when they are mature. But when young, these and other hammerheads do have their threats, particularly from other big sharks. The biggest threat comes during their vulnerable early years in the shallow coastal nurseries.
Many species of Tiger Shark, and Great White Sharks are two of the biggest threats. Their territorial waters often overlap and these sharks have no objection to taking on a hammerhead. The killer whale is another common predator.
Hammerhead Shark fins are also a valuable, though illegal, making them a target for illegal poaching and hunting too. Those that are caught as bycatch when fishing for other species, also rarely survive, making humans one of the biggest predators and threats to these species.
Conservation Status And Efforts
All species of Hammerhead Shark are listed in the IUCN Red List of vulnerable species. Most of the Hammerhead sharks are endangered or critically endangered, and the rest are either labelled as ‘data deficient’ or ‘vulnerable’. Not a single species is believed to be unthreatened, and none have a stable population.
The Galapagos Marine Reserve does provide a safe haven for these sharks, but migratory species like hammerheads lack protection when they leave the reserve’s waters. Conservation work, including tagging and tracking of pregnant female hammerheads, is ongoing, to better understand their behaviour. It is hoped this can improve efforts to provide better protection along their migratory birthing routes.
5 Fun Hammerhead Shark Facts for Kids
- Hammerhead sharks have a unique hammer-shaped head that helps them sense other sea creatures using electric fields and currents!
- Baby hammerhead sharks are born alive and ready to swim!
- Hammerhead sharks can only be outside of the water for up to two minutes before they suffocate and die.
- A large hammerhead shark nursery was discovered in 2017 in the mangroves on the northwest coast of Santa Cruz Island in the Galapagos.
- Hammerhead sharks are not aggressive towards humans; there has never been a human fatality caused by a hammerhead shark!
The 10 Hammerhead Shark Species
While Hammerheads are most often seen in groups around the Galapagos, they can be found in waters around the globe. Different species can be found in their own range and each is uniquely identifiable. Here is a table of all the different species of Hammerhead, along with some important data for each.
|Species||Location||Size||Conservation Status||Identifying Features|
|Winghead Shark – Eusphyra blochii||Tropical and warm temperate waters around central and western Indo-Pacific||Up to 1.9m||Endangered||Extremely wide head, small body|
|Scalloped Bonnethead – Sphyrna corona||Eastern Pacific Ocean, coastal waters from Mexico to Peru||Up to 1.5m||Critically Endangered||Small size, shovel-shaped head|
|Whitefin Hammerhead – Sphyrna couardi||Western Spain coast, West African coast||Up to 1.5m||Data Deficient||White fins, small size|
|Scalloped Hammerhead – Sphyrna lewini||Worldwide in coastal temperate and warm waters – a pelagic species||Up to 4.3m||Critically Endangered||Front edge of head has prominent indentations|
|Scoophead – Sphyrna media||Western Atlantic Ocean coast (from Panama to southern Brazil) and eastern Pacific Ocean (Gulf of California to Ecuador)||Up to 1.5m||Critically Endangered||Small size, scoop-shaped head|
|Great Hammerhead – Sphyrna mokarran||Worldwide in coastal warm waters, particularly around coasts and the continental shelf||Up to 6.1m||Critically Endangered||Largest species, straight front edge of head|
|Bonnethead – Sphyrna tiburo||Atlantic Ocean – the ‘littoral zone’ from New England to Brazil (North Atlantic and Gulf Of Mexico)||Up to 1.5m||Endangered||Small size, shovel-shaped head|
|Smalleye Hammerhead – |
|Coastal waters of the Western Atlantic between Venezuela and Uruguay||Up to 1.5m||Critically Endangered||Small eyes, small size|
|Carolina Hammerhead – Sphyrna gilberti||Southeastern U.S, particularly around South Carolina||Up to 3m||Data Deficient||Similar to Scalloped Hammerhead, smaller second dorsal fin|
|Smooth Hammerhead – Sphyrna zygaena||Worldwide subtropical coasts, from Nova Scotia to Australia. Can tolerate the widest range of waters of all species.||Up to 5m||Vulnerable||The second largest hammerhead, uniquely shaped shape cephalofoil|