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What To Look For:
Hammer shaped head with a nearly straight anterior margin. The
first dorsal fin is very tall and falcate.
Color:
Dark olive green to brownish grey above, white below. Ventral
tips of pectoral fins are not marked.
Size:
This is the largest of the hammerhead sharks. The shark grows
to a length of at least 18.3 feet (5.6m), and may attain a
length of more than 20 feet (16.1m), however, most individuals
encountered by divers are between 10 and 14 feet in length (3 to
4.3 m). Females mature at a length of 8.2 to 9.8 ft (2.5 to 3m);
males mature at a length of 7.7 to 8.8 ft (2.3 to 2.7 m).
Teeth:
Strongly serrate. The tooth formula is: 17-2/3-17 17-1-17.
Habitat:
Coastal-pelagic and semi-oceanic shark occurring close inshore
and well offshore. Found over the continental shelves, island
terraces and in passes and lagoons of coral atolls, as well as
over deep water near land. It is found near the surface and from
depths of 3 ft to more than 262 ft (1 to 80m). It often favors
continental and insular coral reefs.
Distribution:
Circumtropical.
Biology:
• Prey:
The great hammerhead shark feeds on a wide variety of prey, but
favors stingrays, groupers and sea catfishes. It also feeds on
squid, crabs, tarpon, sardines, toadfishes, porgies, grunts, jacks,
herring, grouper, boxfish, other sharks, skates, guitarfish,
cownose and eagle rays.
• Reproduction:
Viviparous, with a yolk-sac placenta. Litters range from 13 to 42
(average 20-40) following a gestation of at least 7 months. Size at
birth is 20 to 28 inches (50 to 70 cm).
Behaviour:
• General:
A solitary, nomadic and migratory species. Some populations move
poleward during the winter.
• Feeding:
The shark feeds mostly at dusk. A shark was seen to use the
underside of its hammer-shaped head to bludgeon and pin a stingray
to the seabed, then the shark pivoted and bit a chunk out of the
ray's pectoral fin.
• Mating:
Mating great hammerheads were reportedly witnessed in 70 ft (21m) in
the Bahamas. The sharks ascended, spiraling slowly around each other
and copulated at the surface. While synchronous swimming as a prelude
to mating has been observed with other species of sharks, copulation
at the surface has not. Most species are though to mate at or near
the seafloor.
Disposition:
The species is thought to be dangerous, though few if any attacks
can be attributed to it because of the difficulty of distinguishing
hammerhead species involved in attacks. In unbaited situations the
shark has approached divers without displaying aggression. However,
due to its size and broad food spectrum the shark should be treated
with caution.
• Danger To Humans:
Due to its large size the great hammerhead shark is considered
potentially dangerous.
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