Scalloped Hammerhead Shark (Sphyrna lewini)


Class: Elasmobranchii
Order: Orectolobiformes
Family:    Rhincodontidae
Size:    Length: 6 to 14 feet (1.8 to 4 m)
Weight: 350 to 991 pounds (160 to 450 kg)
Diet: Many different types of fish, crustaceans and aquatic animals, sometimes other shark species as well
Distribution: Pacific, Atlantic and Indian oceans
Young:  15 to 31 pups
Animal Predators:  Unknown
IUCN Status: Lower risk, near threatened
Terms: Young: Pups
Lifespan: Unknown



·         Female scalloped hammerheads establish dominance over each other by performing corkscrew spins

·         Between 1554 and 1997 there are only two recorded instances of scalloped hammerheads attacking humans.  

·         Many females carry scars from mating encounters, in which the male wraps himself around the female and holds onto her with his teeth.

·         There are eight different species of hammerhead sharks.



Scalloped hammerhead sharks get their name from the deep indentation in the centre of their hammer-like head. The tips of the hammer each bear an eye and a nostril, and are several feet apart. Like all sharks, they have a cartilaginous skeleton and rough skin, and a streamlined body shape. Their colouring is mainly brownish grey, olive or bronze above, with a white belly. The undersides of their pectoral fins have dusky to black tips. Coloration darkens with age, and large, older individuals may be almost black. They have an anal fin, two dorsal fins without spines, five gill slits, and their mouth is behind their eyes. As they move forward, water is forced through the gills, which extract oxygen from the water, enabling them to breathe. 



Scalloped hammerhead sharks are found in tropical, subtropical and moderate climate zones, in the coastal regions of the Altantic, Pacific and Indian oceans. They prefer temperatures averaging 75 F (24 C) or warmer, and are rarely found in water cooler than 72 F (22 C).  


Feeding Habits

Despite popular belief, scalloped hammerhead sharks do not feed often. Because they have a spiral intestinal valve shaped like a spiral staircase, food passes through the shark slowly, so they eat infrequently. They are able to hear low frequency vibrations made by wounded fish, and they have the ability to detect even a small amount of blood in the water, and this enables them to find wounded prey. As they swim towards it, they swing their head from side to side to sample the water with their nose. They eat a wide range of food, including sardines, herring, anchovies, eel and other types of fish, as well as squid, crustaceans, rays and other, smaller sharks. 



Scalloped hammerheads bear their young alive, after a 10 to 12 month gestation. The size of the litter depends on the size of the mother, so litters range from 15 to 31 pups that measure approximately 15 to 22 inches (38 to 55 cm) at birth. Because of their infrequent need to eat, young scalloped hammerheads grow relatively slowly compared to other shark species. They are pupped in coastal lagoons, then migrate offshore later in life. 



Scalloped hammerhead sharks are sociable and tend to form large schools. They are not usually aggressive towards humans, unless taken by surprise or frightened into defending themselves. Although they are fast swimmers, hammerheads do not swim all day. Because they have a liver that is filled with oil, they are able to float for periods of time and rest. 



Although some declines have been reported, scalloped hammerhead sharks are fairly common throughout their range. More studies are being done to determine their status.  



Sharks! Strange and Wonderful, Laurence Pringle (p. 21)
The Living Sea, Orbis Publishing, Robert Burton, Carole Devaney and Tony Long (p. 68-69)
Creatures of the Deep, In Search of the Sea’s “Monsters” and the world they live in, Erich Hoyt (p. 18, 35, 107)
Sharks, Lee Server (p.21, 32)
The Encyclopedia of Sharks, Steve and Jane Parker (p. 64)
Sharks, A Portrait of the Animal World, Andrew Cleave (p. 7, 28, 59)