Alaska's Marine Wildlife
Sea Otters
largest member of the weasel family, but the smallest marine mammal, the sea otter is built for swimming at sea with its long, flat tail and webbed hind feet. The retractable claws on their front paws do not assist them in swimming, but rather are used for foraging and grooming their dense fur. Having a round head with small eyes, a triangular nose, visible ear pinnae, and an extensive, overgrown mustache gives one the impression of a little, old man floating at sea. This impression is further perfected as their head and neck becomes bleached out with age; turning white in old animals. Younger adults have a body coloration that ranges from dark brown to blond with the head being lighter in color. The size of an adult male is typically 5 feet in length and 70 pounds in weight. Females are slightly smaller, weighing 60 pounds and measuring 4 feet in length, on average.
Sea otters become sexually mature at 3-6 years, after which they will begin breeding during the peak mating season, in Alaska, from September through October. They have a variable gestation period of 5-8 months, but in Alaska, a single otter pup weighing 5 pounds and measuring 10 inches, is commonly born to a female each May. Sea otter pups, which are usually born in the water, are dependent on their mothers for a period of 5-12 months, after which they must venture out on their own. Male otters live for 10 to 15 years, while females can survive for 15 to 20 years.
Sea otters have enormous appetites, eating an amount equal to about 25 percent of their body weight each day. Adult sea otters have been documented consuming 14 Dungeness crabs a day. The sea otters retractable claws on its front paws has been found to be advantageous for prying abalone loose from rocks and digging crabs out from within a rock pile. They can dive to depths of sixty feet in search of clams, mussels, sea urchins, or other favorite foods, but will swim back to the surface to eat their catch. Sea otters will only stay underwater for a minute or two while foraging for food, but will spend approximately one-third of their day diving and eating. The meticulous otter will eat while floating on its back, using its chest as a tray to hold its food. To get at the meat in a hard-shelled prey, an otter will use a rock to crack open the shells positioned on its chest, or sometimes an otter will place a flat rock on its chest and, using it as an anvil, will smash shells against it to open them. To protect its eyes from exploding shell fragments, the otter will turn its head aside and close its eyes at the moment of impact. Sea otters will often carry a favored pounding rock in a loose flap of skin under their armpits while they dive for more food in subsequent foraging dives.
Very young sea otter pups can’t dive, so they spend their early life riding on their mother’s chest. However, it is still necessary for the mother otters to make foraging dives to meet the nutritional requirements for her pup and herself. This is a vulnerable time for the young pup due to the threat of predation; bald eagles have been known to swoop down and snatch a helpless pup while its mother is diving for food. In addition, coyotes have preyed upon sea otter pups when they and their mothers have come ashore around Prince William Sound. Transient killer whales may take both young and adult sea otters, but humans have had the greatest impact on otter populations. Because their fur is so thick and luxurious, they were nearly harvested to extinction until they were protected in 1911. Currently their populations are increasing, numbering approximately 150,000 in Alaskan waters, and sea otters have reoccupied much of their historical range.
Sea otters spend a good part of every day grooming their dense, rich fur in order to keep them dry and warm. They have the densest underfur of any mammal, varying in density from 170,000 hairs per square inch on their feet to 1 million per square inch on their forearms (by comparison, a dog has 1,000 to 6,000 hairs per square inch). Unlike other marine mammals, sea otters have very little blubber to keep them warm, but relies on trapped air in their underfur to keep their skin dry and insulate them from the bitter cold sea water. If the fur becomes dirty, oiled or matted it loses its air-trapping, insulating abilities allowing water to penetrate to an otter’s skin, leading to hypothermia and eventually to death. This is why sea otters are so vulnerable to oil spills, like the one that occurred in Prince William Sound in 1989. Therefore, the otters twist and barrel roll in the water and scrub their fur with their forepaws after eating, in order to keep their coats clean. Otters capture air in their coat by floating belly down, blowing bubbles, and rubbing them into the fur. Air trapped in the sea otter’s coat also has a second purpose by functioning like a buoy to keep the animal afloat.
Sea otters are most commonly encountered in the Kenai Fjords National Park, in Prince William Sound, in Glacier Bay and throughout the Inside Passage. Hundreds may be seen holding hands, floating together in a sex-segregated "raft," while resting.
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Harbor Seals
seals are medium-sized, torpedo-shaped pinnipeds with relatively large, round heads and short limbs. The size of the average adult is 6 feet in length and weighing 250 pounds. Their coloration varies from almost black to nearly white with contrasting colored spots, rings, or blotches. However, it is their big, brown eyes that make them so irresistible.
Harbor seals are opportunistic feeders in that they will eat what ever they can catch. Their diet consists of a wide variety of schooling fish, such as sand lance, herring, and smelt, and flatfish, cod, salmon, squid, octopus, and crustaceans, such as shrimp. Seals will often go up rivers to feed upon fish that travel upstream on the high tide, then haul out at low tide to sleep until the next rising tide. In turn, transient killer whales, sea lions, bears, and humans prey upon them, and bald eagles will sometimes take a pup.
In Alaska, Harbor seals breed in July through August and females give birth to a single pup the following May or June after a 10 month gestation. Harbor seal milk has 10 times the fat content of cow’s milk; so seal pups grow rapidly. Pups are 3 feet long and weigh 25 pounds at birth, and within a month, they will have doubled in size. It is imperative that they do so because the pups will be weaned from their mother at 4-6 weeks. Harbor seal pups will become breeding adults in 3-5 years, and can live for 30 years in their coastal waters or estuarine habitats.
Harbor seals are solitary in water, but haul out on remote intertidal sandbars, rocky shores, or ice floes, in groups numbering in the hundreds. Individuals in a group are more efficient at watching for predators than a single seal; therefore seals in a colony can get more rest. After harbor seals haul out on land, they rub, scratch, yawn, sleep, and scan the area for predators from time to time. Harbor seals usually rests on land or ice in a banana-shaped position that appears to be quite uncomfortable.
Unlike sea lions, harbor seals can’t swivel their hind flippers forward to assist them in walking, nor can they elevate their abdomen off the ground. Therefore, they are quite slow and clumsy on land; they steer and brake with their front flippers and just drag their rear flippers behind them. Watching them ambulate on land in a writhing and humping fashion makes them look like pudgy inchworms
During the summer months, harbor seals are commonly found in fjords, such as ones found in Glacier Bay, Prince William Sound, Kenai Fjords National Park, and Tracy Arm Fjords. Hundreds of harbor seals haul out to have their pups on top of drifting ice floes in glacier-fed waters, which offer refuge from terrestrial predators, such as bears. In addition, orcas don’t usually hunt in these silty, ice-choked fjords. For example, deep within the West Arm of Glacier Bay lies Johns Hopkins Inlet, which contains the largest breeding concentration of harbor seals in Alaska, with an estimated 5,000 to 7,000 seals! They are attracted to the safety of the iceberg-choked inlet where they can haul out on bergs, give birth, and nurture their pups..
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Steller Sea Lions
for their lion-like roar, long whiskers, and a thick mane-like ruff, the Steller sea lion was first described by a German naturalist-explorer, Georg Steller in 1741. They are the largest sea lions, with the biggest bulls weighing in at eighteen hundred pounds and up to eleven feet long. The females weigh on average about one-third as much as the huge bulls, and are about 3-4 feet shorter. These efficient predators grow so large due to their diet of pollock, cod, herring, salmon, squid, and octopus. The pups are dark brown at birth, but fade to a light brown to blond coloration as adults. The adults undersides and flippers retain the dark brown color, though. When swimming in the water, they appear to be tan in color.
As mating season approaches each year in May, male sea lions head to the rookeries on rocky islands where they will fast while defending their breeding territories. They won’t eat for the next 60 days, as all of their energy is spent getting face-to-face with other breeding males. With heads roughly the size of a grizzly bear, they try to intimidate each other by growling, hissing, and neck jostling. Occasionally, these threats will escalate into serious fights with biting. The females, who are gregarious during the mating season, arrive at the rookeries in late June, and tend to ignore territorial boundaries and combating males. She will not hesitate to cross a territorial border, but the male will try to herd her back, often without success. After 11.5 months of gestation, she will give birth to a single, 45-pound, 3-foot pup, and then mate again within 10 days. A nursing female will give her pup almost 2 quarts of fat-rich milk per day, and she will lactate for 1-3 years. Two weeks after they’re born, pups are swimming in tide pools, and within another two weeks they are taking short trips offshore with their mothers.
Steller sea lions become sexually mature in 3-7 years. Male sea lions apparently live a rougher lives since their life expectancy is only 20 years as compared the female’s expected lifespan of 30 years. These sea lions live primarily in coastal habitats, and they especially seek out secluded rocky islands for haulouts and rookeries. A great place to spot Steller sea lions is in the Kenai Fjords National Park, where they especially like to haul out on island at the entrances to Aialik and Nuka Bays. Other prime Steller sea lion haulouts are in Prince William Sound and in Icy Strait in the Inside Passage.
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Humpback Whales
humpback whale is a black-bodied, stocky cetacean with some white on throats, belly, and commonly on flippers. Characteristically, they are individually identified by biologists who recognize their black and white patterns on their flukes, which they show prior to making a deep dive. Adult males average 46 feet and weigh 25 tons, while adult females are slightly larger at 49 feet and attain weights of about 35 tons. Their dorsal fins are small, while their flukes are broad with an irregular trailing edge. They have long flippers that are equivalent to one-third of their body length and that expands out like wings when they heave themselves out of the water. This fact was not lost on the scientists that gave them a Latin name that means, "big winged."
Humpback whales are frequently observed performing their high-energy display of catapulting their forty-seven-foot, thirty-ton bodies almost completely out of the water. This spectacular leaping display, known as breaching, is an incredible, awe-inspiring sight. Why these ostentatious cetaceans do this is not fully understood, but they are probably trying to remove barnacles or parasites from their bodies, or they may simply do it because they enjoy it. These aquatic acrobats may also be seen flapping their long flippers on the surface of the water in a manner that could almost be construed as waving at you. Female humpbacks also use their flippers to caress their calves. When a whale shows its flukes, as if to signal goodbye, it usually means that it is going to make a long, deep dive for up to 20 minutes to a half-hour.
Humpback whales, which eat herring and other small schooling fish along with small, shrimplike crustaceans known as krill, are clever hunters, catching fish with a technique known as "bubble-net feeding." As a method to concentrate its prey, one or more whales swim in circles below a school of fish, and blow bubbles as they spiral upwards. This creates a curtain of bubbles, which acts as a "net" when the fish ball up in the middle of the bubbles. The whales then burst through the center of the conglomerate with their baleen-roofed mouths wide open, scooping up great numbers of fish with a single lunge to the surface. Humpback whales will also roll on their sides to utilize a technique called "flick feeding" by using their flukes to concentrate and stun food.
The upper jaw of a humpback whale contains long plates of material called baleen, instead of teeth. When feeding, a humpback will take in about 500 gallons of water at a time, filtering it through the baleen plates, and trapping as much as 100 pounds of krill and other food. During their summer stay in Alaska, humpbacks will consume up to two tons of food per day, giving them the 3- to 4-inch-thick layer of blubber needed for the fall migration.
Female humpback whales usually gives birth to a single calf every 1-3 years after a gestation period of 11.5 months. At birth the calf will weigh about 2 tons and will measure about 12 feet in length. The calf will lactate for 6-10 months, and will then become sexually mature in 4-7 years. If the young whale isn’t preyed upon by transient killer whales or by humans, then it can live a long life of about 50 years.
Many humpback whales spend the summer months feeding in nearshore waters along the southern coast of Alaska. The largest concentrations of these whales are in the Inside Passage, in Prince William Sound and in the waters of the Kenai Fjords National Park. One of the prime places to locate these magnificent creatures is Icy Straits, which is located at the mouth of Glacier Bay National Park. The best method used to spot humpback whales is to look across the water for their blow, which is the cloud of vapor that humpbacks force through their blowholes as they surface and exhale.
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