Gray Whale, Eschrichtius robustus

Gray Whale, Eschrichtius robustus. Whale photographed in coastal waters off Puerto Adolfo Lopes Mateos, Baja California Sur, March 2019.

Phylogeny:  The Gray Whale, Eschrichtius robustus (Lilljeborg, 1861)  is a member of the Eschrichtiidae  Family of Gray Whales. They are marine mammals in the Order Artiodactyla. This places them in the same order as hoofed ungulates, from which they evolved. They are in the Infraorder Cetacea, the Baleen and Toothed Whales. The Escherichtiidae Family consists of only one species, the Gray Whale, Eschrichtius robustus. Historically there were two genera in this Family during the Pliocene Era, 2,580,000 to 5,330,000 years ago, and just one in the Miocene Era, 5,330,000 to 23,000,000 years ago. Presently there is just one family member, the Gray Whale, Eschrichtius robustus. The family and genus names refer to Daniel Eschricht, a Danish zoology professor. In Mexico this species is called ballena gris. Early whalers called Gray Whales “Devil Fish” because of their ferocious response when harpooned.

Morphology:  Gray Whales are large bodied, with a dorsal hump and 6 to 12 smaller bumps running along the ridge from the dorsal hump to the flukes. The flukes and flippers are of moderate size. Viewed from above, the head is narrow and tapering. The mouth is slightly arched. They have mottled gray coloration. Whitish barnacles, scars, and whale lice are usually scattered about the body and head. They raise their flukes when diving. Gray Whales measure 4.9 m (16 feet) at birth and weigh around 680 kg (1,500 pounds). Adults reach 15 m (49 feet) in length and weigh 35,000 kg (80,000 pounds).

Habitat and Distribution:  Gray whales are generally found in open ocean waters, over the continental shelf. Most of the time, they are in shallow coastal waters. There are at least two distinct populations of Gray Whales- the Eastern North Pacific and the Western North Pacific. The Eastern North Pacific population breeds and calves in warmer lagoons and bays along the Baja Peninsula and southern Sonora, Mexico. They spend summers feeding in the cooler waters of the Bering Sea, Chukchi Sea, Southern Alaska, British Columbia, and Northern California. The Western North Pacific population breeds and calves in the South China Sea and feeds in the Sea of Okhotsk. Historically, in Mexican waters Gray Whales were found throughout the Gulf of California. Whaling activities appeared to extirpate them from the northern Gulf. Within the past few decades there have been occasional sightings at least as far north as Bahia de Los Angeles. They are found along the entire west coast of the Baja Peninsula, either migrating or in their calving grounds. Laguna Ojo de Liebre (Scammon’s Lagoon), Laguna San Ignacio, and Magdalena Bay are primary calving locations along the Peninsula. Tojahui/Yavaros in the Mexican state of Sonora and Bahia Santa María in Sinaloa are the primary calving locations along the mainland coast. The North Atlantic population of Gray Whales was thought to have been extirpated since the 1700’s. Within the past two decades, sightings of Gray Whales in the Atlantic Ocean and Mediterranean Sea have given hope that Gray Whales are either recovering in that area, or vagrant whales are moving in from the Pacific. Eastern North Pacific Gray Whales migrate south, in the fall, for 2 to 3 months, covering 8,000 to 11,000 km (5, 000 to 6,800 miles). The return the following spring. They seldom venture more than 10 km (6 miles) from the coastline during migration.

Diet:  Gray Whales can feed either benthically or planktonically.  When feeding on plankton they roll onto their side, skim the water with their mouth open, and filter out the food by expelling the water through their baleen plates. With this method of feeding, they eat crab larvae, polychaete worms, herring eggs, various other forms of larvae, and small fish. When benthic feeding, they roll onto their side and scoop up sea floor sediments, expel the sediments through their baleen plates and filter out food such as amphipods, isopods, polychaete worms, mollusks, and other invertebrates. Gray Whales have also been observed lunge feeding on anchovies, though this seems to occur rarely.

Predators:  Orcas are the primary predator of Gray Whales. White Sharks will also attack Gray Whales calves or injured whales.

Reproduction:  Gray Whales reproduce through sexual reproduction, with internal fertilization. The gestation period is between 12 to 13 months. Females calve at two to three year intervals. Calves mature within seven to nine months, in time to be independent for the next southward migration.

Ecosystem Interactions:  Gray Whales host Whale Lice (cyamids) and three species-specific types of barnacles.

Human Interactions:  Aboriginal hunting of Gray Whales has occurred for hundreds of years. Commercial hunting in the North Atlantic caused the extirpation of the North Atlantic population of Gray Whales in the 1700’s. Commercial hunting of the Eastern North Pacific population began in the mid-1800’s, primarily in the Baja calving grounds. This significantly reduced the population, to the point where targeting this species was no longer commercially viable. International protections put in place during the past several decades have allowed the current population to reach around 20,000. This was sufficient to remove them from endangered status under the United States Endangered Species Act. The IUCN Red List currently list them as a species of Least Concern. The Western North Pacific population has not faired as well. They are down to about 250 individuals, and are listed as Critically Endangered. Aboriginal hunts are still allowed in Russia. Poaching of Gray Whales, vessel strikes, entanglement in fishing gear, and inappropriate whale watching activities are among the greatest threats that Gray Whales currently face.