Range: The Great Hammerhead is a coastal-pelagic,
semi-oceanic shark meaning that it is most commonly found
close inshore and well offshore, over continental shelves,
island terraces, and in passes and lagoons. They exhibit a
cosmopolitan distribution, spanning from North Carolina to
Brazil and the Gulf of Mexico in the Western Atlantic. They
can be found at depths ranging from 3-1000ft (1-300 m).
Similar Species: The
Scalloped Hammerhead (Sphyrna lewini) is similar in
appearance to the Great Hammerhead Shark. The head is the
easiest distinguishing characteristic between these two
species. While the head of both exhibit a curved front edge
with a median indentation, the Scalloped Hammerhead Shark’s
head is more strongly curved. Additionally, the Scalloped
Hammerhead has internarial grooves which are absent in the
Great Hammerhead.
|
Great Hammerhead
exhibits a straighter frontal head form |
Scalloped Hammerhead has
a more strongly curved head |
Identification: The Great
Hammerhead exhibits the characteristic hammer-shaped head
from which it gets its common name. The front margin of the
head is nearly straight with a shallow notch in the center,
distinguishing it from the smooth hammerhead and scalloped
hammerhead. The dorsal side of the great hammerhead is dark
brown to light gray or even olive in color fading to white
on the underside. The largest of the hammerheads, the Great
Hammerhead has been reported up to 20 feet (6.1 m) in
length.
Note: It is thought that
the hammer-shaped head evolved to maximize the area of
sensory organs, such as the Ampullae of Lorenzini which
sense electro-magnetic fields as well as temperature
gradients. The ability to sense electro-magnetic fields
given off by muscle movement aids the Hammerhead in
detecting prey even when the prey is buried in the ocean
bottom. The hammer shape also allows Hammerheads to scan
significantly larger areas of the ocean bottom when hunting
than is capable by other shark species.
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