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Marine Mammals
First Marine Mammals
It was at least 45 million years ago that animals resembling pigs or cows began to feed along the shores of ancient seas. As the numbers of animals feeding along the shoreline increased, some of the animals were forced into deeper water to find food. This pressure on the shore line and the animal probably forced them to begin diving for plants growing in deeper water. Diving for food became a practical way of making a living, and from this beginning, the largest animals to live on the earth began to evolve. These animals are called marine mammals. Marine mammals are now found in all of the world's oceans and seas. The evolutionary development of marine mammals is probably the most remarkable in the animal kingdom.
"Marine Mammal" Defined
A marine mammal, like its land-dwelling counterpart, is warm-blooded, is fur-bearing or has rudimentary hairs, and nurses its offspring. All mammals give birth to live young.
There are three major groups of marine mammals found here: cetaceans (whales, dolphins, and porpoises); pinnipeds (seals, sea lions, elephant seals); and sea otters.
The story of the evolution of land mammals into marine mammals can be told by how much the original terrestrial features have changed. Evolution has transformed the basic land mammals into a creatures beautifully adapted to life in the ocean. Their adaptations enable them to swim, dive, breathe, keep warm, and find food in cold, dark, hostile saltwater environment.
Adaptations
The torpedo shape is the latest form for swimming. This spindle-shaped body is circular and thickest near the center of its length like the body of a dolphin. To further reduce impediments to swimming, other body parts have been eliminated or changed through evolution. The external ears are very small or nonexistent. Sex organs and mammary glands retract into the body when not in use. Testes have moved back into the abdomen. Limbs and feet have vanished or changed into flippers. New body parts such as fins and flukes have evolved to stabilize and propel the animal. The hair lies flat so mammal can pass smoothly through the water.
To keep warm in icy cold waters, marine mammals have large appetites, and rapid digestion provides the calories to fuel the high metabolic rates, which produce heat. Loss of heat is minimized by the thick layer of blubber or, in the case of the otter, with a very thick fur coat.
Changes in the circulatory and respiratory systems have supplied marine mammals with sufficient levels of oxygen to withstand long dives. In addition, the heartbeat slows; blood is sent only to essential tissues and organs; metabolism and body temperature decrease; stored oxygen in the myoglobin of the muscles is released; and higher levels of carbon-dioxide and lactic acid are tolerated.
The livers and kidneys of marine mammals are super-filters that remove excess salts from the blood and prevent dehydration. Fresh water is obtained from the fish eaten. Nursing mothers conserve their own body fluids by producing a thick milk, rich in fats. The babies metabolize the fat to gain the nutrients they need.
Marine mammals have excellent underwater vision for finding prey. Toothed cetaceans also have a sonar-like system called echolocation. Teeth, baleen, cooperative hunting and feeding, and tool-using are only a few of the structural and behavioral adaptations that have allowed various marine mammals to successfully exploit the food resources of the sea.
Summer Visitors
During the latter part of summer, other cetaceans are seen off the central coast.Visitors have seen humpbacks, blue whales, dolphins and porpoises searching for food around the rims of the Monterey and Carmel submarine canyons.
Humpback whales reach over 50 feet in length and are stockier than other whales seen here. They differ from other whales by having extremely long pectoral fins. The humpbacks are very dark, almost black on top, with a white underside, and have a small dorsal fin. They are frequently seen breaching and partially spinning as they fall back into the water. They come to our waters searching for anchovies, other small fish, and small shrimp-like animals called "Krill".
Blue whales are the largest of all whales, reaching lengths of 85 feet in the northern hemisphere and weighing well over 100 tons. They are very streamlined, bluish-gray in color, with a small dorsal fin set far back on its body. They frequent our area hunting for the Krill in, above and near the submarine canyons.
If you see white caps on a calm day, there is a good chance you are seeing Pacific white-sided dolphins or common dolphins. The Pacific white-sided dolphin is one of the most abundant species seen in our area. It is about 7 feet long and weigh about 340 pounds. Traveling in a large school, it feeds extensively on fishes in the inshore waters. The common dolphin is comparatively smaller and more slender, with a longer beak. While the white-sided is more common inshore, the common dolphin is more readily seen offshore hunting for fishes.
Protection for the Future
Throughout time man has exploited marine mammals to the extent that many populations are at extreme lows. It was because of this that the Marine Mammal Protection Act of 1972 was placed into law. Now, many species are slowly recovering. The sea otter was hunted for its fur. Other marine mammals were hunted for the oil which is concentrated in their blubber. Whale oil was an early energy source but now petroleum is providing us with energy of that kind. It is no longer necessary to hunt marine mammals because the products that they yield can be obtained from other sources. Marine mammals should be left alone to range freely throughout the oceans. Human involvement should be purely for observation. In this way marine mammals will prosper, and we will continue to learn more about them.



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