Page 44 - Shark

Head like a hammer

Distribution
of hammerheads
Of all the sharks, hammerheads Bonnetheads
Winged
have the strangest shaped heads. hammerheads
Included in the nine species of
hammerhead are the bonnetheads,
which have small head projections.
The winged hammerhead has by
far the widest head, which can be
half as long as its body. Most
hammerhead species live in
warm temperate and tropical
coastal waters. The scalloped
hammerhead is one of the most
common species and occurs in 0 1,200 2,400 3,600 miles
warm waters throughout the world. HammerHead scHools
Large schools of scalloped hammerheads There are more females in schools
than males, but the reason why
congregate in some areas where there are they group together is unclear.
features on the seafloor like undersea peaks, These large predators have few
enemies, so it is unlikely they
or sea mounts. A hundred of these sharks school for protection. The females
compete with each other (often
may form a school with them all swimming butting one another) to stay in the
in unison. At dusk they swim off on their own center of the schools. This may give
them a better chance to be courted
to feed (pp. 18–19) and then at dawn they by the males.
regroup in the same place.
difficult diet
Stingrays are the
favorite food of the
great hammerhead
even though their
tails are armed with
venomous spines,
or “stings,”. Hammer­
heads do not seem to
mind being stung—one Blue
individual had nearly a spotted
hundred spines sticking into stingray
two different sHarks its mouth and gullet.
The shape of the hammerhead’s head (top) Mouth
compared to that of other sharks—like the
tope (bottom)—fascinated early naturalists. First dorsal fin Gill slit
a fine bonnet
Bonnetheads are the smallest of the
hammerheads, reaching only 5 ft (1.5 m) long
compared to the great hammerhead, which
can grow as much as 20 ft (6 m) long. They
usually swim together in small groups, but
sometimes huge schools of hundreds
of sharks congregate near
the surface.

Pectoral
fin

wHy a
Hammer?
No one
knows why a
hammerhead has a hammer­shaped head, but the broad, flattened
head may give extra lift to the front of the shark’s body as it swims. The
Anal fin Pelvic two hammerheads (right) differ slightly in that the scalloped one (left) has
fin an indentation in the middle of its head, while the smooth one does not.

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