Dolphins Essay, Research Paper
Dolphins
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:
You see, what I have found after twelve years of work with
dolphins is that the limits are not in them, the limits are in
us. So I had to go away and find out, who am I? What?s
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
the basis of its sequence in time and space, like written words
or the Morse Code) using variations in pitch and frequency.
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)
What Warshall is reminding us is that the cetacean?s information are much more advanced than the information of a human being, possessing not just one , but two ways to communicate.
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)
This proves the theory that dolphins use sonar instead of using their eyes to see. Their sonar
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
brain.(McIntyre 135)
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
which their own evolutionary history leaves them quite
unprepared.(McIntyre 36)
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).
These pollutants were found on Britain?s coast. John Harwood of Mammal Research Unit has done tests on a dolphin lying dead on the shore of Britain:
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).
This epidemic has spread all the way to the Gulf of Mexico where thirty-three dolphins have washed up in Alabama and Mississippi. Kennedy states we think an epidemic is possible:
?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,
and it would simply have to burn itself out. ?If large numbers die,
at least we know in advance what?s causing it,?(qtd. Dolphins in Danger 13)
The scientists know where the virus is located, but there is no way of stopping it because there is no possible way to find a cure right know. The only hope is that it just goes away.
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
apart.(Bonner 6)
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
across the television screens around the world, the solution
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)