By Dr. Erich K. Ritter
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The bull shark (Carcharhinus leucas) belongs to
the potentially dangerous sharks. This rather large species can grow to a length
of 350 cm and weigh 230 kg.
© Shark Info /
Doug Perrine
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The first problem is already revealed in the question. Sharks are basically not
dangerous. Only circumstances may lead to situations which are potentially dangerous for
humans. Now many people may feel this is splitting hairs. But there is a big difference
between animals which are considered dangerous and certain situations which may be
potentially threatening.
Many situations pose no threat whatsoever to humans, even though a large shark may be
swimming around. The dangerous shark is just as rare as the nonaggressive shark. Obviously
there are species which - simply due to their size - should only be approached with great
caution, for body size is a problem when it comes to dealing with sharks. Still, even though
most sharks shown on television or in aquariums are mostly imposing in size, it must be
emphasized that of the over 460 shark species only a small fraction of them grow so large as
to cause serious injuries to people. Most are much too small to accomplish this. However,
size alone only plays an indirect role. Much more important is the fact that many large
species of sharks seek prey whose size is comparable to that of human beings.
In order to attack their prey, sharks inevitably need the respective "tools". Undoubtedly,
shark teeth can cause serious wounds on humans. However, these teeth were developed
amidst a natural environment unrelated to humans in order to guarantee survival in the
natural environment. Yet human beings often tend to view nature and its inhabitants from a
very narrow-minded, anthropocentric perspective which may completely overshadow the
true circumstances. For the genuine danger is not the mere presence of sharks but rather the
fact that the size of people who find themselves in the ocean clearly falls into the spectrum
of prey sought by large-sized sharks. This fact, combined with the shark's inability to analyze
the human "objects" enountered whose vibrations make sharks believe they are prey, are
the most essential factors explaining the possible danger of sharks (also see
Shark Info
2 / 98: "Shark attacks - a continually fascinating mystery"). The root, or imminent danger, is
then controlled by the shark's inhibition threshold which prompts him to either approach an
unfamiliar "object" or avoid it. The inherent danger is thus not the animal itself but rather
the fact that by virtue of his size, man fits perfectly into the shark's range of prey, that
humans spend time in areas where sharks live and hunt, and that sharks cannot analyze and
eliminate us from their normal palette of prey.
If we go by the official list of dangerous sharks (e.g. from the
International Shark Attack File
ISAF, an institution which analyzes and collects reports on shark attacks) the white shark
(Carcharodon carcharias) ranks first, followed by the tiger shark (Galeocerdo
cuvier) and the bull shark (Carcharhinus leucas). Most ranks are established
on the basis of questionable
shark accident statistics which leave the reader with the impression that approximately 78%
of all attacks were not provoked by humans and that the amount of "unprovoked" attacks
by white sharks even amounts to 98.7%.
But does this really mean that a shark practically always bites without having been
provoked beforehand? That is exactly what statistics such as those stemming from the ISAF
would like us to believe. The fact is, however, that when analyzing the situation in greater
detail, the victims usually put themselves into situations, or already found themselves in
situations which sharks find challenging or provoking and which prompt their reaction.
Attack statistics must thus avoid reverting to useless and undiscussed numbers. Innocent
readers who accidentally come across such Internet statistics may otherwise receive a
completely wrong picture on the realistic danger surrounding sharks. Not only because the
numbers are twisted to the disadvantage of sharks, but also because opportunities are
wasted to find explanations for what really happened. In addition, not everyone is familiar
enough with sharks to realize that these tables include species which only reach a maximum
length of 50 cm (e.g. cookie-cutter sharks Isistius brasiliensis) who pose no real threat to
humans. And yet: According to the ISAF even these dwarfs among the numerous shark
families allegedly make unprovoked attacks!
Of course it is legitimate to connect accidents with "danger", but many
of the accidents
listed must be questioned. Nonetheless, when such statistics are used as a benchmark for the
potential menace of sharks, it is clearly proven that only about 25 out of 460 existing species
of sharks have been involved in an accident more than once. In addition, 10 to 15 other
species have only been involved in an accident once. Accordingly, potentially threatening
situations can be reduced to 9% of all shark species. However, this small percentage does
not allow us to draw any conclusion on their frequency. Larger animals, i.e. species, are
found in substantially less numbers than their smaller relatives due to their energy
consumption. Thus, the omnipresent hysteria connected with the few shark species who
under certain conditions can actually cause damage and are classified as potentially
"dangerous", is in no way justified.
We shall now briefly define the three most important species related to
accident statistics,
explaining what makes these animals so exceptional. Even though all other species should
be included, these three are listed in their behalf. To the accidents: The "unprovoked" attack
is only a label which is tagged on these animals. A finer analysis would show that human
beings make the most mistakes in these encounters.
The "danger" connected to this species is undoubtedly associated with its size and the
curiosity with which it approaches its alleged prey. Great whites, as well as other species of
sharks, have no way of precisely analyzing an unknown potential prey. In rare cases, they
will test the object with their jaws, inspecting it with their taste buds. Their curiosity must,
however, not be equated with actually biting. The "unprovoked attacks" cited in over 98%
of the accident reports are thus not only wrong, but also represent an erroneous description
of a biological function.
Rumors often say that white sharks mistook surfers for seals and thus attacked them - a
very appropriate theory if one considers sharks to be stupid. However, these and other
theories only found acceptance because no one doubted or disproved them (also see
Shark Info
2 / 98: "Shark attacks - a continually fascinating mystery"). Latest research shows,
however, that many supposed "facts" are nothing more than the initial impressions of
scientists. Since scientists from earlier generations were neither able nor willing to
substantiate their theories, and since current research funding is usually applied in other
areas, such theories continue to be considered standards by which all incidents are measured.
A new generation of scientists is now putting their efforts into more detailed investigations
and verification of these old theories. Statements to the effect that white sharks mistook
surfers with seals, or that they attacked and then retreated to protect themselves from the
claws or bite of the victim, will soon only be cited as anecdotes. The real "danger"
surrounding these animals is more the fact that their behavior is stigmatized with too many
unanswered questions. Although swimming or diving with white sharks certainly must go
hand in hand with great caution, the timing is appropriate to refute their long-term
reputation as being "notorious beasts", a description which may have filled movie houses but
which in no way reflects their true nature.
The tiger shark is undoubtedly the least described but most questioned species of large
sharks. Although found more frequently than the equally large white shark, it was never
made the focus of behavioral research. Tiger sharks probably have the most perfect teeth
structure of all sharks which, combined with their size, enables them to successfully kill
almost every category of prey. Contrary to old theories which regard omnivorous animals as
primitive, current research is based on the assumption that this type of diet represents a high
type of "specialization". When the food supply is low, these animals are capable of changing
from one prey to another. Tiger sharks live in warm waters and are thus predestined to
come into frequent contact with humans. Their broad spectrum of prey makes possible
confrontations more likely, also because humans unconsciously emerge as competitors. Both
tiger sharks and white sharks are curious animals, a characteristic which, however, must not
be mistaken for being aggressive because it simply reflects the nature of these animals.
Many people believe that these are the "most dangerous" of all sharks: They are fast, strong
and are endowed with teeth which need not fear comparison with those of its tiger or white
shark counterparts The real problem with this shark species is more the fact that they like to
spend time in shallow waters close to the shore and often also in river estuaries. Rivers carry
fresh water and much live food which often dies when coming into contact with salt water.
The broad palette of food attracts a wealth of organisms - including sharks. However, only
few species of sharks can survive in brackish water and this requires physiological
adaptations which can stress the shark's body. The mixture of fresh and salt water is mostly
enriched with a high concentration of organic and anorganic substances, resulting in limited
visibility. The bull sharks which roam these regions must not only cope with physiological
adaptation but also with an overdose of electrical fields which stem from all these
substances. Limited visibility can lead to confrontations with humans and to accidents
because their biting inhibition is considerably reduced due to the unusual environmental
conditions.
All shark species which at some point in time were involved in accidents should theoretically
be described in their biological composition. Up until now this has been lacking, so that
somewhere and at some time when one single shark has bitten someone - most likely
because it was provocated - generations later the entire species is labelled "dangerous",
irregardless of whether or not this one particular animal was really "guilty" or not. There are
no limitations in people's minds when it comes to generally denunciating sharks because of
shark accidents! Still, hope remains that later generations will finally begin to realize and
understand how to properly assess any danger or risks in connection with this animal.
(10145 characters)
*Dr. Erich Ritter is a shark biologist and senior scientist at the Green Marine Institute and
Assistant Professor at Hofstra University, New York.
May be published only by indicating the source: Shark Info / Dr. Erich K. Ritter
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