Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Chondrichthyes
Order: Carcharhiniformes
Family: Sphyrnidae
Genus: Sphyrna
Species: Sphyrna mokarran
Size:
Great hammerheads are born between 50 and 70 cm (19.7 to 27.6 inches) and can grow to a gargantuan
6 m (19.8 feet). However, the vast majority do not exceed a maximum length of 3.6 m (11.7 feet). The males reach maturity 234 to 269 (7.7 to 8.8 feet),
while females are sexually mature at 250 to 300 cm (8.2 to 9.8 feet). Great hammerhead sharks posses a virtually straight anterior margin of the head
with a deep central indentation. They have high second dorsal fins and the pelvic fins have curved rear margins. The teeth are triangular with
extraordinarily serrated edges, becoming increasingly oblique toward the corners of the mouth. Their coloration varies from deep olive green to
brownish grey above and white below.
Distribution:
Circumtropical
Habitat:
Great Hammerhead sharks are found in both open ocean and shallow coastal waters. During
summer they may make small migrations towards more northerly areas. The great hammerhead is observed in deep water off the fore reef, in channels,
on the reef flat and in lagoons.
Reproduction:
Great Hammerhead sharks are viviparous. At a length of 3m, maturity is reached.
The gestation period is about 11 months. Litters are made up of between 20 and 40 pups. Young are born in the summer season and are approximately
70 cm in length. Head shape of a newborn pup is more rounded than that of an adult but this changes as they grow.
Feeding:
This species, which hunts most actively at dusk, feeds on sharks, bony fishes
(including catfishes, toadfishes, jacks, herring, groupers and boxfishes), squid, and crustaceans (including shrimps,
crabs and mantis shrimps) that occur on or near the bottom. Larger specimens seem to have a particular fondness for skates
and rays (including guitarfishes, butterfly rays, whiptail stingrays, cownose rays and eagle rays), which it has been observed chasing in shallow water.
Behavior:
Unlike the scalloped and smooth hammerhead this is a solitary species. Some
populations display migratory behavior, moving into warmer waters in the winter. This shark has been reported to be avoided by other
shark species, possibly because of its taste for elasmobranch flesh and its superior maneuverability. .
Distinguishing Characteristics:
One of its most impressive characteristics is its large, orca-like dorsal
fin. The hammer-shaped head of this species is nearly straight along the front edge with an indentation in its center. It is the only
hammerhead with falcate pelvic fins. The free tip of the dorsal fin is in front of the pelvic fin origin and there are no markings on the
pelvic fins (as with the scalloped hammerhead).
