There are many differences between Dolphins and Porpoises. People might think that the two are the same mammal, but they are not. Dolphins have cone-shaped teeth and porpoises have spade-shape teeth. The easiest way to tell them apart is that the porpoise is smaller in size and is broader across the back. Dolphins are classified in the Delphinidae species and there are thirty to fifty different kinds of species in this family(Minasian 204). The Porpoises are classified under the Phoceonidae family which is Latin for pig-fish. Dolphins are the smartest mammals in the ocean. Navy ships have used dolphins to detect mines in the water and search out enemy submarines. Dolphins are very friendly mammals; there are places in Florida where one can ride the dolphin in the water many dream of such a ride.
This dream might not come true if people and different companies keep on killing them. We need to recognize the value of these dolphins and the dangers facing them, and get to stop these dangers and save this amazing creature. The three main dangers and threats to dolphins are pollutants, tuna boats and people.
Dolphins are very sacred creatures to many people. When two dolphins are in a symbol with one pointing up and the other one pointing down it symbolizes ?The duel cosmic streams of involution and evolution? (McIntyre 31). The symbol is the way of showing how the dolphin evolved and where it is going. The dolphin by itself means ?Allegory of Salvation inspired in the ancient legends which show it as the friend of man?(McIntyre 31). It tells the fable of a dolphin saving a man.
The ancients believed that the dolphin represented the vital power of the sea or water which symbolizes the source of life. The Greek word for dolphin is Delphys which means womb and is known as the ?living womb of the sea of creation?(McIntyre 34). Many of the Gods were based on the dolphin because they believed it could partake in mythological forms. There are many stories about dolphins and gods and how they help the gods from the sea. There are also a lot of symbols that represent the dolphins in little story blocks. This is probably why dolphins are a form of good luck or sacred to us in this century(McIntyre 33).
Dolphins are among a very few mammals and animals with the intelligence similar to our own. Cetacean (which is what dolphins, whales and porpoises are classified under)brains are larger than human brains in memory and conceptual thought. There are three animal types with comparable mental equipment; these are humans, elephants and cetaceans. Humans are superior in the physical sense, but might be lacking in the intelligence phase. According to John Lilly:
dolphins is that the limits are not in them, the limits are in
this all about?(qtd. McIntyre 57)
What Lilly is saying is basically that the dolphins have no limits, they can keep going and do anything for a long time, but we limit ourselves and while we are doing this the dolphins are gaining more intelligence.
The dolphin uses sonar like in a navy ship to detect dangers and other things in the waters. Sonar is a device using underwater sound waves for navigation, range finding, detection of submerged objects, communications and etc.(Readers Digest Dictionary 1278). Since their echolocation system gives them detailed images of objects in the ocean, they might be able to recreate sounds and project images to one another. According to Peter Warshall:
Both man and cetaceans seem to have a tremendous capacity
for digital information exchange (information understood on
Cetaceans may also have analog communications systems
which are so different from our own that we may not
be able to perceive them. (Analog information is information
you understand because the data itself is like what you are
talking about. For example, the word ?loud? spoken loudly.)
It seems, too, that digital speech is used mainly to refer to
manipulable objects, while analog communication deals with
more subjective items like emotions. In this sense, it may
be that Cetaceans have the ability (using their clicking
apparatus) to communicate digitally as well as analogously.(qtd. McIntyre 58)
The way the dolphin communicates is through sound. Sound is its primary sense in the ocean. The reason dolphins use sound is that it is too hard to hunt at night in murky waters because dolphins are so deep the light doesn?t penetrate the water. Thus, they use sound to tell if it is loud or soft, fast or slow, high notes or low notes, short silences or long silences and many other combinations(McIntyre 133). Dolphins evolved two kinds of voice; one is for social communication and the other voice is for navigation and location. The echos they receive are synthesized by the brain into images and information; for example: distance, direction, speed, shape, texture, density and the internal structure of the object. Warshall has written about an experiment with dolphins:
A trainer taught a dolphin to approach a lit electric bulb.
the dolphin always performed correctly but never looked
at the light bulb. The confused trainer hid the light bulb.
He turned it on and, sure enough, the dolphin swam
towards it. The trainer figured it out: dolphins prefer to
listen-to hear the click of the light switch-rather than look.(qtd. McIntyre 134)
is like our eyes. They can see anything and tell everything that is happening around them:
Sonar is a way of ?seeing? with sound. The dolphin sends
out a short click or ping which hits a fish and bounces back.
The Dolphin hears the echo and interprets the size, texture,
speed, location, and other characteristics of the fish from
the echo. An echo can be placed between the outgoing
clicks. In this case, the dolphin interprets the returned
unaltered echo. An echo can also be placed so that it
interferes with the outgoing click. In this case, the
dolphin must interprets the amount and kind of distortion
in the echo.(McIntyre 134)
Bottlenose dolphins have been trained to utilize their sonar to tell the difference between two metals and the thickness of them. Dr. Kenneth Norris did an experiment in which a dolphin could tell the difference between a half inch long gelatin capsule filled with water and a piece of fish the same shape at twenty feet(McIntyre 134). This is useful to dolphins because they use sonar in hunting so they don?t chase after the wrong prey:
A dolphin can see detail using his sonar-sight by changing
from low to high frequencies. When sound waves
encounter a fish with great rapidity (high frequency) they
return many more echos. Each echo provides an additional
detail for the dolphin as he forms a sound picture in his
This is how sound travels in water. Sound is energy.
The way Cetaceans create sound is by a disturbance-an explosion-by snapping the jaws shut, popping a bubble or slapping the flukes. This compresses the water and the variations in the disturbance makes the water ?sound? differently(McIntyre 136). No one knows how the cetaceans produce their sound, but they are guessing it is the air that is recycled in the lungs just as with people who play the saxophone and other instruments like it.
Hearing in water for humans is very hard, but dolphins, who don?t listen through the ears, have other ways of listening. The way they hear is through the jaw and the forehead region or melon. The sound hits the jaw and travels in a thin oil inside the jawbone to the inner ear drum. The way they hear from the melon is that sound enters the oil filled melon and passes though air passages to the inner ear drum(McIntyre 138). The construction sounds in an oceanarium have been known to be so severe it has killed a dolphin in the nearby tank. When it rains, the noise in the outdoor tanks are so painful for the dolphins they leap out of the water just to escape the sounds like that the rain makes when hitting the water. The reason why this doesn?t affect dolphins in the ocean is because they can dive deep enough to avoid the horrifying sound. This is the way the dolphin and other mammals in the ocean listen to one another, but it can be painful if the sound is too high in frequency for the dolphin to take. Nevertheless, dolphins are the only animals on earth that can hear such high tones and be alright with it.
These amazing dolphins have been threatened by man for a long time. Ever since the beginning of time, humans have tried to eliminate their rivals. First it was the Homo Neanderthalensis; then they went on to kill most of the elephant species and other large mammals. In the present century the humans have applied their knowledge to killing off whales:
The cetacean system appears to be a more integrated and
contemplative one, evolved in conditions where immediate
danger was not so likely as it was for most mammals. It is
ironic that our technology, which developed as an adaptation
to danger, has now presented the whales with dangers for
Cetaceans evolved so they could figure out what dangers were ahead, but now that technology has kicked in, it is harder to figure the dangers out because they are not used to the unnatural forms they take.
There are chemicals in the water that kills many of the cetaceans members. People are careless and dump pollutants and other things in the ocean that are very harmful to the species. One of the first occurrences of pollutants found in the ocean was Polychlorinated Biphenyls and DDT?s. Polychlorinated Biphenyls are a very excessive chemical found in tar and used in lacquers and preservatives of citrus fruits(Readers Digest Dictionary 141). DDT?s are a powerful insecticide which are effective on contact( Readers Digest Dictionary 342).
The tests on stranded dolphins were prompted by the
discovery of a baby Bottlenose dolphin, which was beached
in Cardigan Bay, Wales. The baby dolphin had more PCB?s
and DDT in its tissues than animals from a badly polluted
Wadden Sea off the Dutch coast. ?For the levels to be so
high in an animal so young is very worrying,? said John
Harwood. Some dead porpoises stranded in the same place
also had high concentrations of these pollutants.(qtd. in Mackenzie 22)
If the waters in Britain are this bad, no marine life will have a chance to live because the pollutants will kill them with in time of them catching it. The way the dolphins get these pollutants are from the food they eat. They accumulate them in their blubber and the toxic pollutants are released when the dolphin has to live off the blubber when it is ill, pregnant or in stressful times.
Hundreds of dead dolphins were found on the Mediterranean beaches. These dolphins were killed by a virus similar to the one that killed 20,000 seals in the north sea. The dolphins died from pneumonia, because the virus destroyed the brains and lungs which caused their death. Just as with an outbreak among humans, this is the dolphins? plague and according to Seamus Kennedy:
The outbreak is the Mediterranean resurrects fears that the
virus could infect all types of marine mammals, including
whales and the endangered monk seal. ?From what we know
about the behaviour of morbilliviruses in terrestrial mammals,
they are extremely virulent and spread rapidly through a
susceptible population.? said Kennedy. Rinderpest , a
morbilliviral disease of cattle, for example, can kill every animal
in a herd that has not been exposed to the virus before. ?There
is no reason to believe that the virus won?t behave the same way
in marine mammals.? said Kennedy.(qtd. Mackenzie 22)
This disease is like chicken pox or even something worse, for this disease can kill. This disease could start out like a common illness and wind up as an outbreak like AIDS. This epidemic is spreading north to south from the centre around the Balearic Sea. Approximately fifty dolphins and other mammals have washed up on different coast on the east side of the Atlantic ocean. ?We know that both seals and porpoises are so susceptible to these viruses. The chances that the monk seals are not susceptible are so slim as to be non-existent? said Kennedy(qtd. Dolphins in Danger).
?Because we find a few animals positive, it means that the
virus is around in a population of high susceptibility,? he
says. He adds that there is no practical way to halt an epidemic,
at least we know in advance what?s causing it,?(qtd. Dolphins in Danger 13)
Researchers have believed that mysterious deaths of thousands of mammals in Europe and United States have resulted from TBT. TBT is tributyl tin found in paint on small boats which is used to keep barnacles from sticking to the hull. This is probably the most toxic substance ever knowingly introduced to the sea(Pearce 5). The scientists believed that the porpoises picked up the compounds from the food. According to Hisato Iwata:
He suspects that butyl tin compounds may be linked to the
mass deaths of several marine mammals populations in North
Atlantic waters since the 1980’s. The animals appeared to
have died from an epidemic morbillivirus, probably triggered
by some unknown agent suppressing their immune systems.
Iwata says that immunosuppression is ?one of the most
representative toxicities of butyl tin compounds.?(Pearce 5)
They think that the butyl tin may have caused the epidemic morbillivirus which means boats are contaminating the water and killing the dolphins.
The next biggest problem is that dolphins are being killed by nets from tuna boats. In 1992 more than a hundred dead dolphins washed up on the coast of Devon and Cornwell caused by fishing nets. There were marks of net rope on the dolphin that suggested this scenario. In Britain the one hundred and eighteen dolphins were the most mammals killed in their records. The vets searched for what happen:
They looked for signs of the highly infectious morbillivirus
that killed tens of thousands of seals in the north sea in the
late 1980’s, and later caused the deaths of hundreds of
stripped dolphins in the Mediterranean. They did not find
any. Nor was there any suggestion that the dolphins had
suffered from a parasitic disease or pollution.(Bonner 6)
This is how they came to the conclusion it had to be nets because the dolphins didn?t die from any disease, but had marks on them. The scientists then put two and two together and they figured out it was the nets. This also tells them that the dolphins were basically murdered by fisherman just so they could get their fish.
Thirty to thirty-eight of the dolphins examined had bad marks around the beak and flipper areas. They also had other marks that told the examiners that they were caught up in nets. A couple of dolphins had lost their flippers and other parts because the fisherman had to sever the parts to get the dolphins free from the entanglement:
The dolphins died suddenly, with fish still undigested in
their stomachs. The species of fish, mainly mackerel and
pilchard, and the narrow mesh of the nets marks, suggest
that they were caught by purse seiners or pair trawlers,
large boats which ran a net between them up to a kilometre
The fisherman didn?t care what got caught up because they could have shortened the net and watched where they dropped, but they only cared about one thing and that was catching the fish.
Dolphins killed by tuna fleets are expected to be less than five thousand in 1993. In 1992 15,470 died in nets(Marine Conservation News 22). This is a huge increase and no one cared; they just wanted to make money.
Six years ago when a heart-breaking video of a dolphin
thrashing in the net of a Panamanian tuna boat was flashed
for once seemed blessedly simple: Ban the fishing gear and
practices that enmesh the sleek, endearing mammals along
with yellowfin tuna. Congress and the food companies
reacted swiftly. With in a couple of years, the U.S. tuna
market was essentially closed to all but ?dolphin safe? fish.(Carpenter 71)
This story is why tuna companies should stop fishing with nets and dragging them all over the water and maybe find a different way to catch their tuna. Finally, the government came through, but it was still late because another dolphin had died a horrible death.
Five years ago the Eastern Pacific was a killing field for dolphins. Over the past thirty-five years six million cetaceans were killed from the tuna boat?s nets. The dolphins were caught in the nets because tuna swim right underneath the dolphins and this is how the dolphins get captured. Tuna boat captains now have special orders and hopefully this might work:
Before a net is hauled in the captain backs up the boat, allowing
escape channel for trapped dolphins. Skippers also use a special
net with a panel of fine webbing to prevent dolphins from
snagging their beaks and drowning. Moreover, each tuna boat
is granted an annual dolphin kill quota. If a skipper exceeds his
limit, he must stop fishing on dolphins for the year, and the excess
is deducted from his allotment for the next year.(Carpenter 72)
This is a good technique, but they shouldn?t kill any dolphins. The new quota should read: if they kill one dolphin they will lose their boating license and be fined heavily. With the safe nets, they should have no problem keeping dolphins alive. The government should also only let a certain amount of boats to tuna hunt and they should all be professional?s. That way we will have no dolphin killing.
Tuna boats have tried several methods of keeping dolphins away from nets. The first method is by bombing and the second is using fake fish. The bombing procedure works like this. First they find a school of dolphins and then a helicopter or speed boat drops a seal bomb to disorient the dolphins. This method allows the fisherman to net both dolphins and tuna and once they are caught up the fisherman drop another bomb to chase the dolphins out the other end of the net. However, environmentalists say ?the dolphins get caught up in the nets still.?(Anderson 19) Congress finally has done something right:
In the late 1988, the U.S. Congress banned the use of
explosives more powerful then seal bombs, which were
exempted from the legislation pending further studies. Last
November, the national fishery service concluded that no
explosives should be detonated within one and a half feet
of the dolphins(Anderson 19).
The Fisheries Service stepped in and told the boats what to do because the government was too scared.
Dolphins and porpoises forage for food with the help of sonar.
Like bats, they send out sound waves and make sense of their
environment beyond the range of their sight from the echos they
receive back. ?It?s as if the animal has a spotlight on top of its
head, a bit like a miner?s lamp.? says David Goodson., but fishing
nets are too fine to reflect the sonar. ?Essentially, the net is
acoustically invisible to the dolphins.(Coghlan 18)
If they can find a way to make the nets sonar built, then the dolphins will steer away from them and there will be no dead dolphins. The design of the experiment is a lightweight ball: ?The curvature of the inner surface is critical and must be exactly right to give the required reflection from any angle approached?(Coghlan 18). The dolphins are supposed to swim over the nets, but instead they swam around them and then after it was clear they went back to the original course after they bombarded it with sonar. Goodson says ?a much larger scale test is now required to optimize the reflection design and spacing(Coghlan 18). The only hold back for this project is the money needed for the research and without further support this idea will fail.
Humans have directly caused some of the dolphin?s deaths too. The humans alone have done this without any weapons, chemicals or nets. According to C.A.L.M(Department of Conservation and Land Management):
dying because their mothers have become dependent on
food handed out by park rangers to entertain tourists. The
and vulnerable to disease and attack by predators.(Anderson 5)
The rangers are killing the dolphins and the tourists think it is fun. If the dolphins become weak then they will die from sharks and other enemies because they are so weak they can not fight
back. In 1975 tourists were feeding four female dolphins and only two of these dolphins are still alive . The females produced seventeen offspring and only five remain. The mortality rate was seventy percent since 1986(Anderson 5)
Even sometimes dolphins kill their own kind. Nineteen healthy dolphins were stranded on the beach and died because they followed their leader. Every one of the dolphins were healthy except the male leader, the one they followed. Paul Jepsen says ?Sick cetaceans often beach themselves?(qtd. Anderson 5). This is just like a cult doing what ever the leader does. According to Jepsen:
There are three theories about why groups of dolphins
become stranded on beaches, he says. ?It may be through
disease, or because they chase fish inshore or because of
some sort of navigational error–perhaps because their echo
sounding systems do not spot gently shelving beaches.? The
autopsies showed that none of the dolphins had been eating
fish immediately before they die.(qtd. Anderson 5)
This is the fault of the dolphins, even though they are supposed to be the smartest mammal then why are they doing this to themselves.
After all the killing of dolphins by tuna boats, the government has finally made some rules against these fishermen. Tuna companies have agreed that ?they will no longer sell tuna caught by methods harmful to dolphins?(?Tuna w/o Guilt? 63). The companies will put out a label on all cans that will say ?Dolphin Safe.? According to Senator Joseph Biden:
The Tuna company will put a DOLPHIN SAFE logo on its cans,
and may have to charge ?a couple of cents more? to account for
higher costs, O?Reilly said. The dolphin-free promise was matched
on the same day by the other two major canners, Bumble Bee
Seafood and Van Camp Seafood which sells Chicken of the Sea
brand. Environmentalists responded with glee. ?It was an incredibly
responsible action.(?Tuna w/o Guilt? 63)
The canners have agreed as well that ?They will no longer accept tuna caught in the region, unless it has been harvested without saving the dolphins as well?(?Tuna w/o Guilt? 63). When they had announced that the tuna fish would be made dolphin free, they said ?It symbolized the triumph of ecological values that not only can not be measured in dollars and cents, but have no obvious human benefit at all, this ones for the dolphins?(?Swim With the Dolphins? 76). Heinz made the first move to ensure tuna fish to be dolphin safe. Following them were other companies. Heinz did this in concern for customers and in taking this step, it received post cards and letters from concerned school children. Ted Smyth says: ?Hopefully in a few years the safest place for tuna will be swimming
underneath a dolphins.?(?Swim With the Dolphins? 76) If a law is passed that tuna boats can not net around dolphins then tuna will not have anything to worry about because they swim with the dolphins and no one will be able to get to them.
Health experts urge Americans to live longer by eating more fish, but environmentalists warn that netting tuna had already killed 80,000 dolphins. There is concern for this because they are the most intelligent creature next to humans. Now the tuna boats sail behind the banner ? We Love Dolphins.? The problem is that tuna love dolphins too, and love to swim with them. When the boats throw the nets around the dolphins, they just hope to find tuna below, not realizing the danger they are causing to other creatures besides the dolphin:
Dolphins are not yet completely safe. Giant fishing vessels
towing 30-miles-ling drift nets strip mine the sea of both
mammals and fish. Their effectiveness is so complete that
The United Nations has called for an end to their use. And
then there?s pollution. When half the Bottlenose dolphin
population on the U.S. mid-Atlantic coast died, the government
suspected a natural red tide was to blame. But many scientists
wondered whether PCB?s found in the dead creatures, often at
levels fifty times higher then the levels allowed in fish, had
weakened them first.(?Dolphins Get a New Reason? 14)
Finally the government understands that the nets are very dangerous to the dolphins and other cetaceans in the ocean. Now what the dolphins have to worry about is PCB?s, and if they get attacked by anything then they will be defenseless because they will be so weak.
Another problem the dolphins have to face is captivity: ?Hearts are won over when these marine mammals perform, but many critics believed that it is cruel to keep them in captivity?(Riley 58). Laws were passed in South Carolina banning any public display of captive dolphins and whales and in Australia their capture and display has been ban since 1988. The Miami Dolphins football team has a dolphin that is in a tank so it can perform for the fans during halftime. Lawsuits were filed against New England Aquarium over treatment of the dolphins.
existed between the dolphins and humans since the time of
Homer will continue. Even Scientists trained to observe life
with strict objectivity, recognize the human urge to find ?a kindred
journey itself, not some place you arrive at. Dolphins live that way
every day. (Riley 67)
Dolphins and man have always been close and will be like this for years to come. Dolphins live
life in happiness because they don?t realize the danger people cause them.
Dolphins are fascinating creatures which people already know, but now people are understanding them better. We have lost a lot of dolphins over many of years and hopefully people, fishing boats, and chemical plants will watch what they are doing because they are destroying a species that one day could save our lives and be a valuable source. Look at what the dolphins did for the navy during wartime. They helped guide the ships through mine fields and spotted the enemies ships and other things to help the U.S. in the war.
Maybe Congress or even the president will pass a law that prohibits tuna boat fishing unless they can come up with a way not to kill or hurt the dolphins. There are still many dangers out in the ocean that are killing dolphins and hopefully in the future we will be able to find them all and cure them so not another single dolphin will die. Remember dolphins are mammals and they are very close to us so we should protect them as we protect our own species.
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Bonner, John ?Mackerel Lured Dolphins to Certain Death.? New Scientist 22 Jan. 1994: 6
Coghlan, Andy. ?Fake Fish Steer Dolphins Away from Danger.? New Scientist 11 Apr. 1992: 18
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Mackenzie, Debora. ?Poisoned Dolphins Prompts Britain to Monitor Life in the Seas.?New Scientist 14 Jul. 1990: 22
Pain, Stephanie. ?Dolphins Virus Threatens Last Remaining Monk Seals.?New Scientist 3 Nov. 1990: 22
Pearce, Fred. ?Dead Dolphins Contaminated by Toxic Paint.? New Scientist 13 Jan. 1996: 5
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