Gray Whale

Description

The gray whale is a medium-to-large baleen whale distinguished by its mottled gray coloration and the extensive patches of white barnacles and orange whale lice (cyamids) that encrust its skin. Adults typically measure 43 to 49 feet in length and weigh between 30 and 40 tons, with females being slightly larger than males. Unlike other baleen whales in the rorqual family, gray whales lack a dorsal fin. Instead, they have a low dorsal hump followed by a series of 6 to 12 bumps or “knuckles” along the dorsal ridge extending to the tail. Their heads are relatively small compared to body size, and the upper jaw is arched when viewed from the side. Gray whales have the shortest and coarsest baleen plates of any whale species, with 130 to 180 plates on each side of the upper jaw, each measuring about 5 to 10 inches in length. Their blow is heart-shaped when viewed from directly in front or behind, produced by their paired blowholes.

Habitat & Range

Gray whales are found exclusively in the North Pacific Ocean. The eastern North Pacific population, numbering approximately 27,000 individuals, undertakes one of the longest annual migrations of any mammal, traveling roughly 10,000 to 12,000 miles round-trip between summer feeding grounds in the Arctic seas (primarily the Bering, Chukchi, and Beaufort Seas) and winter calving lagoons along the Pacific coast of Baja California, Mexico. The coast of Orange County sits squarely along this migration corridor, making it one of the premier locations in the world for gray whale watching. Southbound whales typically pass through Southern California waters from December through February, while northbound whales and mother-calf pairs pass from February through May. Gray whales prefer shallow coastal waters, often swimming within a few miles of shore, and they are one of the easiest great whales to observe from land.

Diet

Gray whales are unique among baleen whales in their primary feeding strategy: they are benthic feeders that suction sediment from the ocean floor to filter out small invertebrates. Their primary prey includes amphipods, particularly species of the genus Ampelisca, along with isopods, polychaete worms, and other small bottom-dwelling crustaceans. To feed, a gray whale rolls onto its side (usually the right side, as evidenced by more wear on the right-side baleen in most individuals) and scoops mouthfuls of sediment, then uses its short, stiff baleen to filter food from the mud. This feeding behavior leaves distinctive pits on the sea floor, which can be observed on sonar surveys of Arctic feeding grounds. During migration and in Southern California waters, gray whales may also skim the surface for mysid shrimp, schooling fish, and crab larvae. They typically fast or feed only opportunistically during the winter breeding and calving season in Mexican waters.

Behavior

Gray whales are moderately social and may be found singly, in pairs, or in loose groups, particularly during migration. They are known for their “friendly” behavior in the calving lagoons of Baja California, where mother whales and their calves sometimes approach small boats and allow humans to touch them. Gray whales are slow but steady swimmers, typically traveling at 3 to 6 miles per hour during migration but capable of bursts up to 11 miles per hour when threatened. They can dive to depths of about 120 meters but usually feed in shallower waters of 50 to 80 meters. Their dives during migration typically last 3 to 5 minutes. Gray whales are known to breach, spy-hop, and engage in other surface-active behaviors, especially during the breeding season. Females give birth to a single calf every two to three years after a gestation period of approximately 13 months. The calving lagoons provide warm, shallow, protected waters where newborn calves can build the blubber layer they need before undertaking the long northward migration.

Conservation Status

The eastern North Pacific gray whale population is one of the greatest success stories in marine conservation. Nearly hunted to extinction by commercial whaling by the early 20th century, the population was protected by international agreement in 1946 and has since recovered to an estimated pre-whaling population size of approximately 27,000 individuals. This population was removed from the U.S. Endangered Species List in 1994. The IUCN lists the species overall as Least Concern. However, in recent years, an Unusual Mortality Event has been declared along the Pacific coast, with elevated numbers of emaciated and dead gray whales observed since 2019, potentially linked to reduced prey availability in Arctic feeding grounds due to warming ocean temperatures. The western North Pacific population, which migrates along the coast of eastern Asia, remains critically endangered with only about 200 individuals. Ongoing threats to gray whales include ship strikes, entanglement in fishing gear, habitat degradation in feeding and breeding areas, and the cascading effects of climate change on Arctic marine ecosystems.