The Gray whale is a giant of the ocean, mottled light to dark gray in color and encrusted with barnacles and whale lice. It has no dorsal fin, instead having a series of bumps on the last third of its back along a dorsal ridge. It has two deep grooves on its throat, which enable its mouth to expand when it feeds. The baleen, which it uses to filter food, is creamy-white. When it surfaces, its 'blow' is distinctly bushy, and is short and ‘heart-shaped’ or forked, as it comes from a pair of blowholes. Females are usually larger than males and otherwise look the same as males.
There are two separate geographic distributions in the North Pacific Ocean of these whales: the Eastern North Pacific stock, which inhabits North America’s west coast, and the “Korean” stock of the Western North Pacific, which occurs along the coasts of eastern Asia. The Gray whale typically lives in coastal waters of up to 100 meters deep. The eastern Pacific whales migrate each year from Arctic feeding grounds to Mexican waters for breeding, whilst the western Pacific whales migrate along Russia’s east coast.
Gray whales feed mainly during the long daylight hours of the summer months and often feed near to the shore where the water is very shallow. They live in small groups, though sometimes form large pods, but don’t stay in the same group for all of their life; instead, the bonds they form are very loose and then they move on to another group. Gray whales exhibit the behavior of “spyhopping” - lifting their heads right out of the water, exposing their entire rostrum for some minutes. They do this while looking out for predators or other whales. They also “breach” (jumping up into the air then splashing down onto their back or side, known also as cresting or lunging), which is understood to be a form of communication, a form of play, and an attempt at removing skin parasites. This whale makes the furthest migration known by any mammal: each spring and autumn they go from their summer feeding waters in the Arctic to the warm equatorial lagoons where the females give birth.
Gray whales are opportunistic feeders and their diet include a wide range of crustaceans including ghost shrimp and amphipods, as well as herring eggs, polychaete worms, and various kinds of larvae.
Gray whales are polygynandrous (or promiscuous); courtship and mating behaviors are complex, and often involve 3 or more individuals simultaneously. They mate throughout the year, though most conceptions take place between late November and early December. After a gestation period of 13 to 14 months, a female bears a single calf, which she nurses until it is the age of 6 to 7 months. Calving grounds are usually in shallow lagoons less than 4 m deep and are hyper-saline. The cows often hold their newborns at the surface in order to help them breathe. They are fiercely defensive of the young against potential predators. The offspring inherit the feeding grounds of their mothers and are often seen in them a year after they become independent. Gray whales achieve sexual maturity from 5 to 11 years of age.
The main threats to Gray whales are shipping and industrial activities along the coastal migratory routes, increasing the risk of entanglement in fishing nets, collisions with ships, and pollution. Habitat degradation from dredging and drilling is also a problem.
According to the IUCN Red List, the eastern Pacific population is 15,000-22,000 whales, while the western Pacific population is only about 100 individuals, of which 20-30 are mature females. Overall, Gray whale numbers are stable currently, western population is listed as Critically Endangered (CR), while eastern population is Least Concern (LC).
Being at the top of the food chain, Gray whales have an important part to play in the marine environment’s overall health, consuming large numbers of their prey items.