Although the gray whale once roamed the oceans of both the North Atlantic and North Pacific oceans, their present range is restricted to the North Pacific and adjacent Arctic seas (the eastern North Pacific population), with a small separate, and distinct population of about 130 animals (the western North Pacific, or Asian, gray whale), whose migratory route is presumed to be between the Sea of Okhotsk and southern Korea. Gray whales are inshore animals, generally inhabiting waters less than 820 ft (250 m) deep. They are also migratory, presumably navigating by following learned routes over the bottom topography and perhaps by following coastal promontories.
The Eastern North Pacific gray whale’s passage from summer feeding grounds in the Bering and Chukchi seas to calving and wintering grounds along the peninsula of Baja California in Mexico is the longest known annual migration for any mammal and is remarkably precise in its annual timing. Each autumn, as chill winds begin to whip across the Bering and Chukchi seas, and the ice pack moves down from the polar cap, thousands of grays abandon the shallow, food-rich Arctic waters and begin their journey toward the warm, protected lagoons of Baja California. There the pregnant females bear their young while other whales relax and swim around the lagoon entrances. In their migration, virtually all of these whales pass through Unimak Pass in the Aleutian chain, and most then follow the continental shelf south past southeast Alaska and British Columbia to Washington, where they encounter and follow the shoreline to Mexico, providing a spectacular sight for coastal residents and tourists who whale-watch from the headlands and coastal sight-seeing vessels.
Pregnant females lead the migration, then adult males and sub-adults of both sexes, following the route that has become a ritual of the species. Gray whale counts at several strategic points along the migratory path indicate that between 18,000 and 20,000 individuals make up the eastern North Pacific stock — a substantial increase from the few thousand whales that survived the first three decades of the twentieth century, when modern whaling ravaged the population for a second time. (Gray whales had been nearly extirpated by American whalers earlier in the 1850s and 1860s). The western North Pacific (or Korean) stock was hunted to near extinction and today there are only an estimated 150 to 300 individuals making up that decimated population. Because this population is so small and because we know so little about them, we are only describing the natural history of the eastern North Pacific gray whales on this website.
On the one hand the recovery of the eastern North Pacific gray whale is a notable achievement in conservation and a measure of the species’ tenacious hold on existence. On the other hand, the western North Pacific gray whale stock is depleted to the point where it might be unrealistic to think of a similar recovery. Contemporary threats to the remaining gray whales derive, not from the direct exploitation that destroyed their predecessors, but from contamination and usurpation of their highly restricted habitat, or intense underwater military sonar — conditions that we still fail to acknowledge as our responsibility to control.