Great White Shark
Order Family Genus&Species
Lamniformes
Lamnidae
Carcharodon carcharias
Sharks have fascinated man for centuries and no
shark is more formidable
or worthy
of our respect and is more feared than the Great
White Shark. These sharks are
the ultimate predators of the deep and
cruise the great oceans, constantly ( it seems)
in search of prey. Great whites normally do
not eat decaying animals but will attack
weak, young and sick animals.
Double rows of serrated teeth are used to slash
and
tear hunks of flesh from victims and when
their teeth fall
out or are pushed out, they
are replaced in two weeks by back row teeth moving
forward to replace the missing
teeth.
These sharks spend much of their time in coastal
areas around seal breeding grounds
and around reefs where there is a plentiful supply
of fish
and other food items. The
Great Barrier Reef off the coast of Australia
has, perhaps, the
greatest concentration
of great white sharks in the world and is a favorite
stalking spot for oceanographers
and other scientists who study the great white
in intimate detail.
The great white is designed for swimming
and it's sleek, streamlined features allows it
to swim great distances without tiring. Although they are mostly
solitary hunters, they
have been known to hunt in groups of two or more.....especially
when stalking prey
which may be too large for one shark to successfully kill by itself.
Great whites hunt by sensing chemicals in the
water, such as blood, and then homing in
on that chemical until it finds it's prey. It also can
sense difference in pressure through
a group of pressure sensors called the lateral
line system and may actually be able to
detect the thrashing of water, such as that of
a swimmer, from over a mile away. They
also have special sensory organs called the ampules
of Lorenzini which are connected
to the pores through long canals.
These sensors can
transmit extremely weak electric
signals to the brain and give the shark
a "roadmap" to the location of their prey. It's
no wonder these denizens of the deep are so adept at homing in on poor
unsuspecting
victims from great distances away.
These sharks may reach a length of over 20 feet
and
weigh over three tons. Females
are generally a bit larger than males
with both reaching
sexual maturity in 6 1/2 to 7
years. There is a variable mating
season with a
gestation period of one year
and the
resulting offspring usually numbering between 1
and 2, although there are rare cases of
3 or more being born. Sharks have a lifespan
of 40 to 50 years.
All sharks are cold-blooded and cannot create
their own body heat, so they will take
on the temperature of the water around them, but great whites are
fast-swimming sharks
and can save heat built up by their muscles as
they swim. Special blood vessels (retia)
carry this heat and keep their body temperature
several degrees warmer than the sea
water in which they live.
Great whites, like all sharks, must keep moving
to keep a fresh supply of oxygen flowing
through their gills ( five slits along
their body, just in front of their pectoral fins). These
gills absorb oxygen for the bodies use just as
our lungs do for us. Injured sharks who are
unable to keep moving forward will sink to the bottom of the ocean
and drown. Great
whites also have holes in the upper part of their
head called spiracles
which draw water
over the gills.....keeping them clear
of sand and other obstacles which could clog up the
gills and cause the shark to drown.
Body tissues of the great white are heavier
than water
and the natural tendency is for them
to sink, but they also contain several buoyancy
aids which help in this area. They have a
cartilaginous skeleton which is lighter
than a regular bone skeleton.....they have a large,
oily liver which takes up over a fifth
of their body volume. This liver contains a
fatty sub-
stance called squalene which has a lighter density
than sea water and helps to keep the
shark afloat.
Sharks have no vocal cords and cannot communicate
with other sharks in an audible
way and it is not known for sure if they
actually do have some way of communicating
with their species.
Although the great white has a reputation as a
savage man-eater, in truth, few humans are
killed or maimed by this species.
Those that are attacked
often live to tell of the
tale and
report the same type incident.......the great white grabs them and
then lets go. This would
suggest that human flesh is distasteful to the
great white. This doesn't mean that great
damage won't be done while the shark is making up it's mind that it
doesn't really want to
eat this human creature after all. One
encounter with a great white might result in wounds
that would require hundreds of stitches to close.
These sharks are rare but are not in danger, at
this time, of having to be put on the endanger-
ed species list and , in fact, great whites
are
protected in California and South Africa.
Great white sharks are found in the area shaded dark blue in the above graphic.
Watch for December's "Creature of the Month"......The German Shepherd.