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July 18, 2002
A: FROM MENTOR KRISTIN TAGHON. TO READ BIO. CLICK
HERE.
Tremana, your question led me to look up info on sharks
which thoroughly
intrigued me! Thanks!! I typed in "sharks attack humans"
and found the web
site:
http://www.field-guides.com/sci/sharks/
It is basically a tutorial on sharks. It is a wonderfully
organized set of web
sites that is put together to teach you about sharks. The
web sites inform on
shark behavior, anatomy, shark attacks and why they may attack
sometimes. I
list a few of the web sites and some of the information, here.
To use the site, click on "Start Field Trip". Once
you do, information in the
bottom yellow frame tells you what URL you are on. The main
frame has the web
site it has found. The lower rightmost square frame has the
controls for
navigating the tutorial Click on the right arrow to move thru
the collection of
web sites. Left arrow to go backwards thru the sites. This
is an amazing site.
Take a look.
The following info on shark attacks was taken from:
http://www.seaworld.org/infobooks/Sharks&Rays/home.html
Click on "Behavior"
1 . Only 32 species of sharks have been identified with attacks
on humans or
boats. These species have three features in
common: they prey on fish or marine mammals, grow to a large
size, and frequent
warmer coastal waters where swimmers are
apt to be.
2. In 1958, the U.S. Office of Naval Research and the American
Institute of
Biological Sciences set up the Shark Research
Panel-a union of scientists that gathered documentation on
shark attacks and
compiled the information into the Shark Attack
File. The Shark Research Panel documented the following:
a. Humans become prey by accident. Most shark attacks involve
people
handling hooked or snared sharks or
spearfishermen handling wounded fish. Through sight or sound,
a shark may
confuse swimmers or divers for prey.
b. Sharks may also attack from a territorial drive, with no
intention to
feed. A characteristic swimming pattern called
agonistic display usually precedes attacks out of territoriality.
The shark
shakes its head and swims erratically with a
hunched back, pectoral fins pointing down, and snout pointing
up.
A characteristic swimming pattern called agonistic display
usually precedes attacks out of territoriality.
3. An analysis of 1,000 recent shark attacks world-wide showed
that well over
50% of the attacks were not feeding-related.
4. Up to 60% of shark attack injuries are slashes of the upper
jaw teeth. This
behavior is typical of courtship advances by
some male sharks.
5. Sharks may also injure victims by bumping them vigorously,
but most sharks
move in cautiously when attacking.
6. A great white shark (Carcharodon carcharias) rushes towards
its prey,
attacking from beneath and behind. These sharks
rely on stealth and surprise to prey on seals, sea lions,
and other marine
mammals.
a. After a great white shark bites its victim, it swims a
short distance
away, waiting for its victim to bleed to death. If
rescuers are nearby, many human victims survive the attack.
b. Great white shark populations may be increasing along the
coasts of
California and Oregon due to increasing
populations of seals and sea lions. Marine mammal populations
are
increasing as a result of federal protection.
Populations of predators naturally increase as food becomes
more readily
available.
c. To reduce the chance of an attack by a great white shark,
swimmers and
divers should stay clear of seal and sea lion
rookeries, or other known areas frequented by the sharks.
d. Swimmers and skindivers at the surface are more prone to
attack than
SCUBA divers beneath the water. At the
surface, a swimmer's or diver's silhouette resembles that
of a seal. Great
white sharks may not be able to make the
distinction.
e. California has one of the highest great white shark attack
rates in the
world. Yet fatalities average only one every eight
years.
7. There is no known effective shark deterrent.
The following web site has very interesting facts about sharks
that I inserted
here:
http://www.vanaqua.org/Visitor_Information/AquaFacts/Sharks.htm
Sharks have no bones! Their skeletons are made of cartilage.
Sharks renew their teeth throughout their lives; as one tooth
breaks off or wears out, another one rotates forward from
the
inside of the jaw to replace it.
Shark skin looks and feels as though it is covered with tiny
teeth.
In fact, their small, rough placoid scales (also called denticles),
have the same structure as sharks’ teeth! Shark skin
is sometimes
used as sandpaper.
Are sharks dangerous?
All sharks are predators.
Most shark species (about 80 percent) have never been known
to attack humans.
Many shark attacks are caused by people getting too close
to
sharks, or provoking and threatening them.
There are four shark species that are always considered
dangerous to humans: great white shark, tiger shark, bull
shark
and oceanic whitetip shark. Seventeen other species of sharks
have also attacked humans. They are considered less dangerous,
but are aggressive if threatened or disturbed. They include
lemon
sharks, blacktip reef sharks (at the Vancouver Aquarium Marine
Science Centre), nurse sharks, wobbegongs, sand tiger sharks
and spitting sharks.
Although they are slow and sluggish, basking sharks and whale
sharks are considered dangerous because of their large size.
How do sharks detect their prey?
The most important sense the shark uses to detect its prey
is
sound. Their acute hearing can detect a struggling fish two
km
away. Sharks do not have external ears. Instead, a tiny duct
carries sound waves to the inner ear.
Sharks can also detect sound with their lateral line system.
This
system is made up of hundreds of pores along a line on the
side of
the shark's body. It is also highly sensitive to wave movements,
pressure changes and vibrations in the water.
Sharks have an incredible sense of smell; some shark species
can
smell one drop of blood diluted in one million drops of sea
water.
Sharks have good eyesight, especially when prey is closer
than
15 m. Sharks have a sophisticated and complex retina that
is
poorly understood at this time.
This URL gives you 10 safety tips to avoiding shark attacks:
http://www.aloha.com:80/~lifeguards/sharimgs.html
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