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Exploring the beautiful nature of California


California Nature:  Marine Mammals


The ancestors of the marine mammals at one time lived on land. Close to 100 million years ago, in some cases, they began evolving into aquatic creatures, resuming life in the water from which their land ancestors had come originally, but with vastly different structures. The earliest known fossil whales go back some 60 million years, to the Eocene epoch. The earliest fossil seals, much less modified than the whales, go back about 20-25 million years, to the Miocene epoch. The sea otters, closely related to present-day land and freshwater mammals, have taken up a marine life very recently. All, however, are peculiarly adapted to their life in the sea.

Young marine mammals are usually born singly (twins being rare), are born with their eyes open, and are fairly large and precocious, as they need to be to cope with the hazards of their exposed marine environment. Little seals, in particular, are very vulnerable on land or on ice floes, and so are their mothers as long as they stay with them.
seals are just some of the marine mammals found offshor of California Whales combat the cold of ocean waters by insulating their bodies with a thick layer of blubber, or fat. Seals have both a fat layer and hair. Sea otters have no fat layer and must depend to a great extent on their dense fur for warmth. The fat layer found on most marine mammals may also serve the purpose of tiding animals over periods of fasting. Whales migrating through areas where food is scarce can go for considerable periods without eating-though it has been questioned whether they draw on their blubber at such times.

Bull seals holding harems may stay on the beach for long periods without eating-in the case of the fur seal for as much as two months or longer. Baby fur seals may stay several days or a week between feedings while the mother goes to sea for fish. The Arctic harp seal mother stays with her baby for two weeks nursing it, then leaves it, the baby stays on the ice floe for two weeks longer, then tumbles into the water and starts catching food for itself. The sea otter, on the other hand, cannot go long without. feeding. Fat in a marine mammal’s body also aids in flotation.
Baleen whales have no teeth but instead have sheets of baleen, used as strainers. However, their ancestors had teeth, and the tooth buds still appear in the embryos.

While some of the toothed whales have large numbers of teeth, others seem to be in the process of losing their teeth, having functional teeth only in the lower jaw, with rudimentary teeth in the upper and sometimes the lower jaw.

A question which often arises is how marine mammals exist in an environment where most of their available drinking water is salty. Seals have not been observed to make use of fresh water in the form of ice. On the other hand, four seals that were shipped in a warm railway car drank fresh water greedily as soon as it was made available to them.
dolphins and porpoises are hard to tell apart in California nature Of all things that have interested people about whales and seals the most fascinating is perhaps how air-breathing animals can dive so deep and stay down so long, and how they can return to the surface without getting the “bends,” or decompression sickness. This sickness, which afflicts human divers, is caused by nitrogen gas, which first accumulates in the blood in dissolved form, then separates out in bubbles if the return to the surface is too sudden.

Sperm whales can stay down as long as 60 to 90 minutes, seals 5 to 15 minutes, and southern elephant seals perhaps more than 30 minutes; yet the lung capacity of marine mammals is not notably greater than that of land animals. In the sperm and bottlenose whales it is only half that of many terrestrial mammals in proportion to body weight and up to one and one-half times in others.

Whales grow to be the largest animals known today. In fact, the blue whale, attaining a length of about 100 feet and a weight of over 100 tons, is the largest animal that ever lived. The finback whale, reaching 70 to 82 feet, may attain a weight of something like 70 tons. Other whales may reach lengths of up to 50 to 70 feet. A 44-foot gray whale weighed about 35 tons. Whales can attain these great sizes because their body weight is supported by the water.
The terms “dolphin” versus “porpoise” almost always create confusion and controversy. Properly speaking, the long-beaked forms are called dolphins, while the small, snubby-nosed forms, especially those of the genus Phocoena, are called porpoises. But the terms are often used interchangeably. To further complicate things, a fish also goes by the name “dolphin.”

Whales and dolphins have always caught the fancy of man, because of their huge size in some cases, because of their beauty and playfulness in others, and because of their amazing adaptation to the strange world of water. Also of course they have for centuries been valuable to man as a source of food and oil, and for a time, of whalebone.
Dolphin      Porpoise      Sea Lions      Sea Otter      Seals     Whales
 
 
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