Dolphin Essay Essay, Research Paper
Life in the sea: the ways of a Dolphin
The dolphin is a very playful and friendly animal. The exact population of dolphins is unknown, for they are found world- wide in many different waters. Food is often hard to find since fish tend to be distributed in ever- moving schools, making the dolphin have to search for its food. The dolphin is usually a very social animal that swims in-groups. The dolphin playful behavior serves as functions of communication, food, herding, defense, as well as just fun and games. A dolphin s life span does not necessarily depend on age but on its predators. The dolphin is one of the most caring and lovable animals.
In the wild, dolphin s travel in groups called pods. Although the exact number of dolphins is unknown, they are found in coastal waters all over the world. In the Pacific Ocean dolphins range from Japan to Australia and New Zealand, and from Southern California to the coast of Chile. In the Atlantic, they are found from Nova Scotia to Norway, extending south to Argentina and the southern tip of Africa. In the West Atlantic, including the Hudson Bay and the Caribbean Sea, dolphins are fairly wide spread. Dolphins are also common throughout the Indian Ocean from the coasts of India and Sri Lanka to the southern tips of South Africa and New Zealand. We are far from knowing the exact ranges for the various populations of dolphins around the world.
The size of a dolphin pod partially depends on its need for surveillance against predators. The dolphins worst enemy is man. Not only through direct killing, but also through pollution and fishing. Dolphins are also prey for sharks, not necessarily for food but for territory. The dolphin does not have many enemies, because they don t cause a threat to anyone.
Dolphins are mammals. They give birth to one baby at a time and are warm- blooded. At birth a dolphin calf is about 90 to 130 centimeters long and will grow to about 4 meters. The female being slightly smaller than the male. A dolphin has a powerful, stream-lined body to allow it to shoot through the water like a torpedo. The dolphin has a dorsal fin on top of its back. It also has two pectoral fins to steer and tail fins called flukes, that propel them through the water. Their blowhole is also located on top of its head for breathing. The jaws on each side of its beak are lined with 20 or more, small, sharp, re- curved teeth for catching fish. It has dark, soulful eyes that are encircled with black markings that extend to the beak and produce a slippery secretion to protect the eyes from foreign objects and water friction.
Dolphins reach sexual maturity after 12 to 15 years of age. Courtship occurs in spring or fall. Males and females court by stroking each other with their flippers, by rubbing their bodies together and by swimming along side each other. After a playful courtship, the dolphins have belly to belly intercourse. The female usually gives birth to one baby, but will possibly carry twins or triplets. Gestation lasts 10 to 12 months. The baby, or calf is born tail first so it will not drown. Once born the calf stays close to its mother not going more than a few feet from her side. The calf feeds on milk from its mothers teats. Since it has no lips to suck, the mother squirts her milk into its mouth with retracting muscles, the baby then goes to the surface for air and then goes back down for more. Dolphin milk has six times more protein and is much more fattening than human milk. It allows the baby to grow 2 to 3 times faster than a human baby does in the six months.
Dolphins spend most of their day searching for food. Their pods are always traveling to keep up with the ever- moving schools of fish. Dolphins hunt both alone and in groups, although you seldom see them alone. Their diet indirectly depends on the size of the pod. Depending on how much food they can find. They feed on small fish and an occasional squid or octopus. Eating the fish whole and tail first. The natural diet of a dolphin also varies according to its home range. Open water pods feed mostly on pelagic fish. Those living in coastal Atlantic waters feed on mullet, hering, smelt, capelin, catfish, eels, shrimp, and other shell fish. Indian Ocean dolphins feed on coral reef dwelling fish and mullet. Dolphins usually eat a wide variety of fish and sea life.
Dolphins are very social animals. And are seldom alone. They travel, eat, and even breathe together. Dolphins are also very social creatures, they are both active and boisterous. They can do many flips and somersaults, some can even jump vertically into the air. What most dolphins love doing the most is bow- riding. They ride off ships and the pressure wave created by whales, and are able to stay with the vessel for several hours. Dolphins are very affectionate. They care for the sick by using their fins to keep them afloat so they can breathe. They also make friend with members of other pods and show obvious emotion towards them. Adults act as teachers to the young. Younger dolphins are disciplined when proper manners are not performed. Mother in the group share the responsibilities in taking care of the young.
A dolphins intelligence lies somewhere between that of dogs and chimpanzees. They have success in problem solving. Have the capacity for sustaining interests and fears. And have moods as well as emotions. Dolphins have many sign, of anger, happiness, annoyance, which they use in the wild and in captivity. For example, slapping of the tail on the water is a sign of annoyance, or a warning to other dolphins of danger. An open mouth or head nodding is a sign of aggression. And violent jaw clapping is a sign of even greater aggression. A dolphin is a very intelligent creature, and has as much natural intelligence as learning capabilities. In laboratory tests, show that dolphins have an extremely fast thought process. Dolphins are taught to push under water levers to earn fish. The brain of an eight foot long 300 pound, adult dolphin weighs about 1,700 grams. The brain of a 150 pound man weighs about 1,459 grams, meaning the dolphins brain weighs approximately two pound more than an adult males. This chart shows how much some animals brains weigh:
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How Much Does The Brain Weigh?
Adult animal: Average Brain (in grams):
Mouse 0.4
Guinea Pig 4.8
Cat 31.0
Dog 65.0
Chimpanzee 350.0
Gorilla 450.0
Man 1,450
Dolphin 1,700
Elephant 6,075
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Weight is not the only way of judging a brain. Ratio of brain weight to body weight is also important. This chart shows that both man and dolphin have relatively large brains for their bodies,
Ratio Of Body Weight To Brain Weight
Animal Body weights Brain weight Brain weight compared
(in pounds) (in pounds) to Body weight
Man 150 3.1 2.1%
Dolphin 300 3.5 1.17%
Chimpanzee 110 .77 .70%
Elephant 12,000 11.0 .12%
Other way to judge the brain:
· The complexities of the brain- both man and dolphins have complex folds, fissures, and convulsions on the brain s surface.
· The cell density of the brain- both mans and dolphins have a high nerve-cell count.
The number of layers in the cortex (the outer part) of the brain- rats and rabbits have four layers of cell types; monkeys, men and dolphins have six.
Again, the dolphins intelligence is between that of a dog and chimpanzee.
Human beings may directly or indirectly seriously affect mortality rates for dolphins. Some have been found with plastic bags and other debris in their stomachs, which can cause internal injury or starvation. Chemical pollution can poison the dolphins food supply as well as the dolphin. Natural death, on the other hand, is usually a result of predators, parasites or disease. Besides man orcas and sharks are a dolphins predators. Nematoads, tapeworms and paracitic flukes infest their internal organs, causing them to shut down. Bacterial and viral infections are not uncommon and studies have shown that they may account for one- fourth of marine mammals stranded or dead. And they can also die from stress related ulcers. If a dolphin lives through predators, parasites, and disease, they can possibly live to be about 40 years old.