MARINE MAMMALS

by Jerry Loomis
Retired State Park Ranger

definition  |   adaptations  |  sea lions  |  harbor seals
northern elephant seals  |  southern sea otters  |  more about cetaceans
pacific gray whales  |  orcas  |  summer visitors  |  protection for the future

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 a 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 sonartype 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.

A Closer Look at the Marine Mammals

Sea Lions
The barking California sea lion (Zalophus californianus) is the most conspicuous of the marine mammals found at Point Lobos. It is also the animal that gave Point Lobos its name. The Spanish named Point Lobos Punta de los Lobos Marinos which means the "point of the sea wolves". Point Lobos is the home of hundreds of sea lions from August to June. During the summer months the sexually active males go south to the Channel Islands. There the males protect an area of females in a harem and mate with females that live on the islands year-round.

Male California sea lions reach weights of 700-800 pounds and can be up to 8 feet long. Females grow to 250 pounds and reach lengths of 6 feet. Sea lions are brown and have external ear lobes. They live on a diet of squid and fish, competing heavily with fishermen for salmon. Sea lions are intelligent animals that are mobile on land. They are able to rotate both fore and hind flippers enabling them to walk or run on land. Sea lions are very vocal as well. Take a few minutes at Sea Lion Point to hear the raucous vocalizations.

Steller sea lions (Eumetopias jubatus) were once common at Point Lobos but now are uncommon south of Point Año Nuevo. These animals prefer to stay offshore and are most often seen hauled out on coastal islands. A male Steller sea lion is three times heavier than a California sea lion. Fully grown males reach average lengths of 10 feet and weigh as much as 2,200 pounds. Females are about one-third the size of males and can measure eight feet long.

Harbor Seals
The harbor seal (Phoca vitulina) is a true seal which has concealed internal ears and short flippers. The shorelines and rocks of Moss Cove, Whalers Cove, Blue Fish Cove, Headland Cove, and Bird Island are areas where this spotted harbor seal can be found hauled out and resting. Harbor seal fur varies in color from light gray to nearly black. Males and females reach weights of 250 pounds and lengths of 6 feet.

Harbor seals, like sea lions, have evolved to utilize a layer of fat called blubber. Blubber is used for warmth and as a source of energy when fasting. These seals are not very mobile on land; however, in the water they are fully capable of capturing free-swimming fishes. Harbor seals are here year-round and do not migrate. They pup in April. Mating occurs when the pup is weaned, up to 6 weeks after birth.

Northern Elephant Seals
The northern elephant seal (Mirounga angustirostris) is the second-largest pinniped in the world. The adult male has a large pendulous snout, measures up to 16 feet in length, and weighs over two tons. The female is smaller, weighing a ton and measuring up to 10 feet in length. They feed on deep-water, bottom-dwelling marine life like swell sharks, dogfish, rockfishes and squid.

Although sightings of adult male elephant seals are rare, occasionally a juvenile elephant seal can be seen at Point Lobos. During the molting phase, when the old pelage is replaced by new fur, the juvenile elephant seal will haul out on the sandy beaches or even on rocky beaches like those at Sea Lion Cove to rest. They can be seen trying to flip sand onto their backs. The eyes become weepy to protect them from drying out, and their overall appearance is like that of a mangy dog. Generally there is nothing physically wrong with these animals, so leave them alone and keep at least 50 feet away. You can report a sighting of a hauled-out marine mammal to the reserve staff, who will check its condition. Año Nuevo State Reserve, just north of Santa Cruz, is the best place to see these animals during the breeding season (December through February).

Southern Sea Otters
The most recently evolved marine mammal is the sea otter (Enhydra lutris). A member of the weasel family, it is related to river otters, badgers, weasels, and skunks.

Sea otters can be observed in Monterey Bay and in the kelp beds of Point Lobos. Prior to their being hunted for the fur trade, they numbered between 10,000 and 16,000 off the California coast, and along with the northern sea otter, in the hundreds of thousands throughout a range from northern Japan to the Baja California coast. Hunting between 1741 and 1911 was so intense that sea otters were finally thought to be extinct in California. However, a remnant population of about 50 otters survived off the Big Sur coast in the early 1930's. With full protection by state and federal laws the population began to recover and expand north and south along the coast. The 1993 census counted about 2,100 southern sea otters in a range extending from Point Conception to Pillar Point.

Having left its land and river habitat for a marine existence only three million years ago, the sea otter has not evolved to the extent that it has blubber. Instead, sea otters have the densest fur of any animal. The coat maintains its insulating properties only so long as the fur is kept scrupulously clean. A sea otter spends many hours each day grooming. A soiled sea otter can die of exposure to the cold water within just a few days.

Sea otters eat a variety of invertebrates, including mussels, clams, abalones, snails, crabs, urchins, sea stars, squid, and octopus. Otters eat many animals that graze on kelps and therefore protect the kelp from being overgrazed. Food is gathered with the forepaws and carried to the surface where the otter floats on its back and consumes the prey. Otters need to eat about 25% of their body weight each day to stay warm. They seldom come ashore and can be seen in the kelp where they rest. When sleeping, the otter may wrap itself in kelp fronds so it won't float away. Several otters may raft together in the kelp. They are not sound sleepers and are easily disturbed by any sort of noise or activity.

Male sea otters are about 5 1/2 feet long and can reach average of 80-85 pounds, and average 62 pounds. Female sea otters are about a foot shorter and lighter than males. Once sexually mature, female otters can pup annually. Mating occurs year-round. During mating, the male will bite the female's nose, sometimes resulting in extensive scarring of the muzzle. Look for the white scar tissue or a pink muzzle on a recently bred female. Pupping can occur anytime after a 4- to 6-month gestation period.

Pups are usually born in the water and receive round-the-clock care. Mom will carry the pup on her chest while at the surface and leave the pup floating like sea otter & pupa cork in the water while she hunts for food. The pup will make a shrill cry calling for the mother. Pups learn to dive at 6 weeks and are weaned by the mother at 5 to 8 months.

Otters have few natural predators, although attacks by white sharks and killer whales have been documented. Humans are by far the most effective predators. Some otters are lost each year to gill net fishing and gunshot wounds. When an oil spill coats the fur, an otter is kept from effectively grooming, and the animal can die in a short time from exposure and the inhalation and ingestion of the toxic oil and fumes.

More About Cetaceans
Whales and dolphins are the most highly adapted of the marine mammals. Most are fast-swimming predators with many adaptations for finding food. They can dive to great depths and hold their breath for a long time. These animals are so well adapted to the ocean that when stranded on land they are helpless and nearly always die. There are two groups of whales: the toothed and the baleen whales. The toothed whales (like killer whales, sperm whales, porpoises, and dolphins) have teeth and a single blowhole. A baleen whale has a series of long plates called baleen that hang from the gumline on the upper jaw to help filter food from the ocean. Baleen whales have paired blowholes.

Pacific Gray Whales
One of the most awesome events in nature occurs annually and is witnessed here during the months of December through April, just offshore. This is the migration of the Pacific gray whale (Eschrichtius robustus), which makes the longest migration of any mammal. This migration can be as long as 14,000 miles. During the summer most gray whales feed on the Arctic seafloor on amphipods and other bottom-dwelling invertebrates. In the fall when the ice starts forming over the feeding grounds, the migration begins. Full-term females (cows) are the first whales to be seen on their way south to the lagoons of Baja California. The calves need to be born in a warm, protected environment that the lagoons offer. The 15-foot, 1,500-pound calves are born without blubber, and therefore have no thermal protection. This situation is soon remedied as the calves begin to nurse on some of nature's richest milk. They are able to gain 8 pounds per hour while nursing and double their body weight in a short time. The fat stores they need to make a 7,000-mile trip will be secured before the trip begins. The cows will lose up to 25% of their total mass during this process. A mature cow may reach 45 feet in length and weigh in at slightly less than a ton per foot. Males are slightly smaller, seldom reaching 42 feet in length. Mating occurs every other year during migration. Gestation is roughly 12 months. Gray whales are mottled by barnacles and whale lice which contribute to their grayish color.

Orcas
These large, toothed whales are actually the largest members of the dolphin family. Black on top with white markings on their sides and below, and with a large dorsal fin, they are easy to recognize. Sometimes, during the spring and summer months, transient pods appear along our coastline. The Big Sur pod is seen all year. These killer whales feed on other marine mammals and fishes and are sometimes seen during the gray whale migration. These killer whales feed as individuals, or in groups as a pod. They will cooperate to hunt and herd fishes, and will attack gray whale calves, and older, unhealthy animals.

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 shrimp-like euphausiids.

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 shrimp-like euphausiids 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.