Gray whales (Eschrichtius robustus) are the only large whales which can be regularly observed in large numbers from Alaska shores. They are found in the North Pacific Ocean and adjacent waters of the Arctic Ocean where they are two geographically isolated stocks: the Korean or western Pacific stock and the California or eastern Pacific stock. The California stock migrates between Baja California and the Bering and Chukchi seas each year, a round trip distance of over 10,000 miles (16,000 km).

General description: Gray whales are the most primitive of the living mysticete (moustached) or baleen whales. They are mottled gray in color and covered with abrasions, blotches, scars, and clusters of parasitic barnacles which are most abundant on their heads and backs, particularly the parts that are exposed to air when they breathe. Gray whales have no dorsal fin but have a low hump followed by a series of 9 to 12 knobs on the dorsal ridge of the tail stock. The upper jaw is narrow and slightly arched, and there are two to four pleats on the throat which allow the mouth cavity to expand when feeding. The flippers are large and paddle-shaped and the tail flukes very broad, their width equalling almost 25 percent of the total body length.

Baleen whales take their name from the horny fringed plates called baleen which hang downward on either side of their upper jaws. The inner margins of the plates are fringed with coarse bristles forming a hairy curtain that acts as a sieve to filter food. Gray whales have the coarsest baleen of all whales, with about 20 bristles per inch (7-8 per cm) of plate as compared to over 100 per inch (42-50 per cm) in sei whales. There are 130 to 180 plates on each side of the jaw.

Distribution and migration: The eastern Pacific stock of gray whales winters in the warm coastal waters of Baja California and the southern Gulf of California. From late February to May the whales begin a northward migration, following the coast closely. They enter the Bering Sea, primarily through Unimak Pass, mostly in April and May, and continue moving along the coast of Bristol Bay. After passing Nunivak Island, they head toward St. Lawrence Island, arriving there in May or June. The whales disperse to spend the summer feeding in shallow waters (usually less than 200 feet (60 m) deep) of the northern and western Bering Sea and the Chukchi Sea. Gray whales begin their southward migration in mid-October, passing through Unimak Pass between late October and early January. They arrive in Baja California mainly in December and January.

Life history: Unlike other large whales, gray whales concentrate in shallow protected lagoons to have their young. The most famous of these is Scammon's Lagoon, named after the whaling captain who first discovered the calving areas. Breeding occurs mainly in late November and early December on the southward migration. A single calf is born in late December to early February of the following year, after a gestation period of about 13 months. Most females bear calves once every two years. Newborn calves are about 16 feet (4.9 m) long and weigh about 1,500 pounds (680 kg).

Gray whale calves grow very rapidly on their mother's milk (which is over 50 percent fat) and are about 28 feet (8.6 m) long by August when they are weaned. Growth slows as the whales reach sexual maturity at about age 8 but continues until the age of 40. Adult whales are about 36 to 50 feet (10-15 m) long and may weigh 16 to 45 tons (15-41 metric tons); females are larger than males at any given age. Although some may live as long as 70 years, 40 or 50 years is the usual lifespan.

Food habits: Gray whales are the only baleen whales that are mainly bottom feeders. They apparently feed by lying on their sides and sucking up sediment from the sea floor. Small invertebrates are captured on the baleen while sediment and other particles are expelled through the baleen fringes. Oblong bowl-shaped pits, measuring about 3 feet by 6 feet (1 x 2 m) are left behind as a record of their feeding. Gray whales eat primarily amphipod crustaceans. Concentrations of 12,000 to 20,000 amphipods per square yard have been found in the southern Chukchi Sea and northern Bering Sea where the whales feed. In fact, that area was called the large “kitchengarden” by Soviet whalers. The estimated daily consumption of an adult gray whale is about 2,600 pounds (1,200 kg). In the approximately five months spent in Alaska waters, one whale eats about 396,000 pounds (180,000 kg) of amphipod crustaceans.

In general, gray whales feed little along their migration route and on the calving grounds. Animals taken by early whalers before the northward migration weighed 11 to 29 percent less than whales of similar length taken on the northern feeding grounds.

Predators: The only major predators of gray whales are killer whales and humans. Many gray whales have healed scars and killer whale teeth marks on their flukes and flippers. Early whalers and Eskimos from coastal Alaskan villages have reported many instances of gray whales fleeing into very shallow water and sometimes beaching or stranding themselves while trying to escape pursuing killer whales.

Behavior: Gray whales are noted for their protective behavior toward their calves. They were called “devil-fish” by Yankee whalers, and Eskimo hunters are wary of them because they sometimes attack boats when their calves were threatened.

They are generally slow swimmers, averaging 3 to 5 miles per hour (5-8 km/hr) during migration. While traveling they make shallow dives of four to five minutes, then surface to blow three or four times. In a single breath, 80 to 90 percent of the air in their lungs is exchanged in comparison to 10 to 20 percent in land mammals. Feeding dives range from 3 or 4 minutes up to 15 minutes.

Gray whales sometimes breach or spyhop, particularly during migration and breeding. During breaching, the whales leap partially out of the water and reenter on their backs or sides with a large splash which can often be seen several miles away. When spyhopping, the whales raise only their heads out of the water, then slip back below the surface. Breaching is thought to be associated with breeding. The purpose of spyhopping is unknown, although some have suggested that the whales are looking for landmarks along the shoreline.

Use by humans: In the 1800s and early 1900s gray whales were heavily hunted. First on their calving grounds and later, with the advent of modern technology, in other areas. It is estimated that by the 1930s only a few hundred to a few thousand remained. In 1948 the International Convention for the Regulation of Whaling banned all hunting of gray whales except by aboriginal people and by contracting governments when the meat and products are for aboriginal use. Since then, gray whales have recovered to pre-exploitation abundance, and their population is now estimated at about 21,000. Since 1960 the Russians have harvested an average of 167 animals per year for use by the Chukchi Eskimos. Alaska Eskimos have harvested an average of two gray whales annually (range 0-6) in recent years.

Text: Kathy Frost
Illustration: Taylor
Revised and reprinted 1994