Aquarium of the Pacific - Online Learning Center - Species Print Sheet
Conservation Status: Safe for Now
Eastern Pacific Gray Whale
(Eschrichtius robustus)Cetaceans • Whales • Mammals • Marine
Whalers called gray whales “devilfish” because of the way they fiercely defended themselves and their calves from being attacked by humans and non-human prey. Today we call them the “friendly” whales because of the way they seek out close contact with humans in selected lagoons in Baja California, Mexico.
At the Aquarium
Due to the space requirements for these intelligent and dynamic animals, we do not exhibit live whales or dolphins. Gray whales are featured in signage. The voices of gray whales can be heard in the interactive kiosk’s Whales: Voices in the Sea and may also be spotted during the whale watch season on one of our whale watching trips.
Seasonally from the Artctic’s Beaufort, Chukchi, and Bering Seas, along North America’s Pacific coast to Baja California, Mexico, Sea of Cortez, and Gulf of Mexico.
Gray whales require different habitats for foraging and reproduction. The water in the subtropical breeding/calving grounds of the Baja lagoons is about 4 m (13 ft) deep, temperature 15-20o C (50-68o F), hypersaline due to evaporation, and the bottom is sandy or muddy with eelgrass growth in some areas. In the Arctic feeding grounds, where 95% of the whales’ food is gammarid amphipods, the bottom is muddy, the water depth under 60 m (197 ft) and the water temperature a frigid 2.8-3.9o C (37-39o F). The “summer residents” of northern California to southeastern Alaska inhabit a variety of temperate water habitats—muddy and sandy bottoms, rock and boulder substrates, and kelp and eelgrass beds with depths from 3-30 m (9.8-98 ft).
Gray whales are mysticetes, baleen whales. They have a robust but slender body tapered at both ends and a small head that appears triangular when viewed from above. Their upper jaw is arched in profile and extends beyond the lower jaw. Their rostrum (top of head) is dimpled and in each of the depressions there is a single, irregular, bristly hair. These hairs are also found along the side of the lower jaw. Called vibrissae, they are tactile sensors like cat and sea lion whiskers. These whales have two to five ventral throat grooves or creases that are about 1.5 m (5 ft) long. Their flippers are small, paddle-shaped, and pointed at the ends. Their flukes are 3-3.6 m (10-12 ft) in width, pointed at the tips, deeply notched in the center, and often frayed, scarred, and scraped (presumably from attacks by killer whales). Instead of a dorsal fin they have a prominent dorsal hump about two-thirds of the way down their back. This is followed by a series of 6-12 bumps or knuckles along the ridge of the back that create a saw-toothed appearance.
These whales have 130-180 overlapping, cream to whitish-yellow baleen plates that fray into fine hairs on the ends inside their mouth next to the tongue. These plates are 5-15 cm (2-10 in) in length.
As their name indicates, gray whales are gray in color but their coloration is not uniform. Younger whales are darker gray and older ones lighter. Both have gray patches, varying degrees of white mottling, and scattered encrustations of whitish barnacles and orange whale lice.
They are are 11-14 m (36-46 ft) long and weigh 16,000-45,000 kg (38,000-99,000 lbs). Their tongue is about 1.5 m (5 ft) long, can weigh 454-1361 kg (1000-3000 lb.
Diet and Feeding
While several whale species feed on the bottom, the bottom feeding technique of gray whales is unique. The gray whale takes a deep inhalation of air, arches its body, throws its flukes high into the air, and dives to the muddy bottom usually in relatively shallow water that is 10-15 m (30-50 ft) deep. On the bottom it rolls on its side (normally the right side) and pushes its head through the top few inches of sediment. It then opens its mouth slightly and by expanding and contracting its throat grooves and retracting its huge tongue creates a powerful suction to suck up the food-filled sediment. It uses its tongue to force the mud and water through the baleen plates on the opposite side of its mouth. The baleen acts as a filter or strainer retaining only the food, which the whale maneuvers with its tongue so the gammarid amphipods, tube worms, mollusks, and other bottom invertebrates can be swallowed. The whale leaves a trench in the ocean floor and trails a plume of mud behind it as it surfaces.
Recent observations have dispelled the beliefs that gray whales are only bottom feeders and that they do not eat during their migrations. Opportunistic feeders, they surface-feed, gulping small schooling fish, pelagic crabs, and swarms of krill when encountered. They also forage in kelp for mysid shrimps.
Gray whales become sexually mature at 5-11 years of age or when they reach 12-14 m (39.6-46 ft) in length. Mating usually occurs during the southbound migration. Courtship is complex and may involve three or more whales of mixed sexes, milling, circling, and rolling for two hours or more. Groups of three are common, usually a female and two males. At one time it was thought that the second male was an assistant, helping to keep the female close to the mating male. Researchers today believe that both males mate with the female.
Not all calves are born in the warm waters of the Baja lagoons. Females with calves are commonly seen on the southbound migration from observation points along the U.S. Pacific Coast. The calf, born after a gestation period of 12-13 months, is pinkish at birth rapidly changing to dark gray to black in color, 4.5-5 m (14.9-16 ft) in length, and weighs about 50-68 kg (1100-1500 lb). The flukes of newborns are weak and curled under at birth with the result that the almost helpless calf usually has to be supported by the mother using her back and flukes to get it to the surface for its first breath of air. Within about three hours the calf becomes coordinated enough to swim a steady course.
The cow’s nipples are recessed in narrow folds on her belly. When the calf’s mouth touches one of the folds, the mother’s muscles push the nipple outward and she forcibly ejects a stream of milk into the calf’s mouth. It rapidly accumulates the blubber layer that will help keep it warm by consuming about 189 l (50 gal) of milk a day that is 50-53% fat and the consistency of cottage cheese. The calf will grow about 3 m (10 ft) and double its weight before its swim north begins. It will be weaned after reaching the Alaskan feeding grounds when it is about seven to eight months of age.
Females with calves usually stay in the back shallow waters of the lagoons with their calves, away from the males and single females (who are often at the entrance to the lagoons). Very young calves may rest or ride on the back of the mother. The pair is often observed “napping” with eyes closed and blowholes at or just below the surface of the water. They surface every 8-10 minutes for a breath of air. As the calves grow they try to mimic the acrobatic behavior of adults. They also practice bottom feeding and are observed in the lagoons with their immature tail stocks and flukes sticking straight up in the air. Before the journey north begins, the female takes the calf to various parts of the lagoon so that it can become stronger and learn how to handle itself in strong tidal currents.
The Blow: Gray whales usually take three to five breaths 10-20 seconds apart, then dive for three to seven minutes, staying underwater for up to 20 minutes. When they resurface, they exhale about 378 l (100 gal) of air in a blow that is up to 4.6 m (15 ft) high. If winds are calm, the blow appears to be heart-shaped.
Acrobatics: Although they are not as noted for their acrobatic behaviors as humpback whales, grays still manage to be “showy”. Why the whales display is not known. Their acrobatics include: breaching: throwing as much as ¾ of the body out of the water and landing on the surface belly down or on the side with a huge splash. Is this to get rid of parasites, communicate with other whales, a courtship display, a temper tantrum, or just for fun? spyhopping:lifting the head out of the water vertically, usually clearing the eyes above the water surface to scan for about 30 seconds, then slowly sinking down. Why look around? Perhaps, to see who is in the area, where obstacles are, to navigate, or just out of curiousity. sailing: lifting flukes and tailstock into the air to catch a strong gust of air and “sail” downwind with the breeze (a lagoon behavior). snorkeling: a rise to the surface to inhale air without a blow, (exhalation is underwater). This behavior is believed to be unique to gray whales. It may be a reaction to boat noises and traffic or a desire to be “hidden”.
The Migration: Eastern Pacific gray whales have one of the longest migrations of any animal. They travel 16,000-23,530 km (10,000-14,000 mi) round trip during their journey from Arctic summer feeding grounds to winter breeding and calving grounds in Baja lagoons and the Gulf of California. The total distance is dependent on the exact starting and turn-around points.
When freeze-up starts and food supplies dwindle in the western Beaufort, Chukchi, and northern and Bering seas, something tells the whales to start swimming south. After feeding for about 20 hours a day, they have managed to gain back a good deal of the weight lost during their migration. Pregnant females leave first in late September to early October, then sexually mature males and females, and last, the immature of both sexes. The peak southern migration off southern California is mid- February. Most of the whales stop in the Baja lagoons while a small number go as far as Cabo San Lucas and an even smaller number, the Sea of Cortez.
By the time these whales start their migration back to the Arctic two to three months later they are lean and hungry having lost 15-30% of their weight and not having had a good meal since they left the Arctic four to six months earlier. Impregnated females leave Baja first starting north as early as late January. The peak of the southern migration along the southern California coast is late February so north and south bound whales are often seen. Cow-calf pairs usually do not leave Baja until April so as to give the calf a maximum time to strengthen and put on blubber. The female stays close to the coast in an effort to protect the calf from transient killer whales. The trip north is slow for the cow-calf pair because of stops for nursing and the occasional meal of mysid shrimp or other food encountered.
Not all gray whales make the entire migration back north. For several years a small number of whales have been regularly observed throughout the spring-summer-fall feeding in northern California waters in the Gulf of the Farallones and Point Reyes Headland, central Oregon, Washington, along the outer coast of Vancouver Island, British Columbia, and southeastern Alaska. Formerly called summer residents, these “short distance” travelers who don’t swim all the way to the Arctic feeding grounds are now called the Pacific Coast Aggregation Group. They join the southbound migration in the late fall.
Gray whales feed in icy-cold Arctic waters for as long as 20 hours a day without becoming hypothermic, despite loss of heat through their cavernous mouths. How do they maintain body heat while taking in gallons of frigid water? They have a number of “countercurrent heat exchangers” scattered throughout the tongue consisting of a single central artery encircled by a network of veins. As the blood circulates, heat is transferred from the warm arterial blood to the cooler venous blood. Scientific observations indicate that a whale loses more heat through its body-encasing blubber than through its not-too-well insulated tongue. It appears that the development of these tongue heat exchangers was as important in the evolution of gray whales as the development of its filtering baleen.
These whales are believed to have a life span of 30-70 years.
At one time three populations of gray whales could be found in the coastal waters of the north Atlantic and north Pacific Oceans. The north Atlantic population became extinct 300 years ago. The western Pacific gray is critically endangered and scientists believe it may become extinct. In contrast, the remarkably resilient eastern Pacific gray whale has twice made a recovery from near extinction to today’s population of about 26,000, equal to what has been estimated to be the pre-whaling number.
In 1971 the Mexican government established Scammon’s Lagoon as a Whale Sanctuary, the first in the world. Subsequent decrees strengthened protection laws and also made San Ignacio, Guerrero Negro, and Manuela Lagoons whale sanctuaries. In addition they were declared Maritime Attraction Zones. The primary calving area in San Ignacio Lagoon was made off-limits to tourism. Eastern Pacific gray whales were removed from the United States Endangered Species List in 1995; however, they are still protected under the Marine Mammal Protection Act. The IUCN Red List rating is LR/CD (lower risk/conservation dependent).
Conservation of gray whales means addressing threats resulting mostly from human activities. These include collisions with vessels, especially in the crowded shipping lanes along the California coast; entanglement in fishing gear, (gill nets, long lines, and lobster pot buoys); reduced food sources due to global climate change in the Arctic; behavior alterations along migratory routes and in the lagoons caused by increasing numbers of whale watching boats and tourists; noise pollution (ship traffic, Navy sonar testing, oil and gas exploration and operations) interfering with their communication; industrial activities and resort development in Magdalena Bay, a calving ground; establishment of LNG facilities in the Baja Peninsula; and the pressures by some countries for resumption of commercial whaling. Also to be considered is whether the available feeding grounds are adequate to support the food needs of the growing population.
The International Whaling Commission (IWC) lists gray whales as a category “sustained management stock permitting”. Under this listing IWC has permitted taking 620 gray whales for aboriginal subsistence in the period 2003-2007 with no more than 140 to be killed per year. Five per year have been allocated to the Makah Native Americans who live on Washington’s Olympic Peninsula and the rest to Siberian aboriginals. Legal action has halted hunting by the Makah who have now asked for exemption from the Marine Mammal Protection Act so as to be able to continue their hunts.
Gray or grey?: In the United States the spelling of the color is “gray”. In other parts of the world it is spelled “grey”. The international community has accepted the American spelling for the whale’s common name so it is the gray whale with an “a”, not an “e”.
Whale harvesting to whale watching: In the early 1870’s a popular weekend outing was a trip to shore whaling stations along California’s coast to picnic and watch whalers bring in gray whales for rendering. Over the years this changed to watching the annual migration of the “California” gray whales from shore. The December 31, 1956 edition of a San Diego newspaper reported that 10,000 people watched 42 grays swim by on their way to the Baja lagoons. The gray whales were approaching extinction when commercial whale watching from boats started in 1955-56 in either San Diego or San Pedro, California. Today, whale watching is not just a southern California industry, it has spread to 87 countries generating more than a billion dollars annually. Right whales in Patagonia; humpbacks in Hawaii, the Caribbean, and Australia; sperm whales in the Azores; finbacks, humpbacks, minke, and pilot whales in the Sea of Cortez; friendly gray whales in Baja lagoons; blue and humpback whales in California’s Santa Barbara Channel—it all started in Southern California with “California” gray whales as the attraction.
A whale of many names: The gray whale’s scientific genus name Eschrichtius refers to a Danish zoology professor Daniel Eschricht and the species name, robustus means strong or oaken in Latin. Then there are the common names: devilfish for its ferocity and violent defensive behavior; mussel-digger for its bottom feeding behavior: scrag whale, the name used by Nantucket whalers, and California gray whale when California laid claim to the species. The latter was replaced with Pacific gray whale because of the objections of the states of Washington, Oregon, and Alaska plus the Canadian province of British Columbia, and Mexico. Today‘s common usage is eastern Pacific or eastern gray whale, and western Pacific, or western gray whale to distinguish the two populations. Some governmental agencies use eastern North Pacific and western North Pacific whales.
Gray whale cleaner fish: When the whales are in the Baja lagoons, topsmelt, silvery schooling fish, serve as cleaning fish for the whales. Normally feeding on marine plants and tiny shrimp, these fish pick at the whale’s barnacles and whale lice as an alternate food source.
Ocean going hitchhikers: Gray whales are one of the most heavily parasitized of all cetaceans. The barnacle species that they host, Cryptolepas rhacianecti, is unique to these whales. The larvae are water-borne through several moltings until they attach to the whales, usually at the time of the sixth molting to become hitchhikers. They burrow into the skin of a whale, especially around the head, back, flippers, and flukes, where they live the rest of their life. When they finally fall off or are scraped off, they leave behind a whitish patch. As the whale grows, barnacles do also—forming large, solid, whitish-brown clusters. Filter feeders, the water column is the source of their food, not the whale itself. The whale just provides a free ride.
There are three species of whale lice that prey on these whales, two of which parasitize only gray whales. Each species occupies a different area of the whale’s body in folds and slits of skin and around the barnacle clusters where there is damaged tissue. Whale lice are not actually lice. They are small crustaceans 1.8-2.54 cm (0.5-1 in) long that act like lice. The whales first acquire them by physical contact with an infected whale. Once attached, new lice emerge from the brood patch on their parents as miniature adults, immediately dig into the whale’s skin with sharp corkscrew-like legs, and proceed to dine on the whale’s flesh.
Aboriginals and the gray whale: Siberia’s Chukotka and Koryak peoples, Alaska’s Inuit and Tlingit, Vancouver Island’s Tse-shahts, Washington’s Olympic Peninsula’s Makah, and the Chumash of California and Baja Mexico—all knew the gray whale. Many hunted them from canoes, ate the meat, rendered the blubber to use as oil for cooking, turned the baleen into combs and brushes, constructed roof and door supports from the bones, and used the vertebrae as stools. Rituals were conducted in honor of the whales—dances to invoke the whale’s spirit and ask for forgiveness for hunting it and songs sung at festivals about its greatness. Some tribes believed that Whale People lived in underground dwellings as men, turning into gray whales when they emerged from beneath the sea. The Chukotka built memorials to the whales that still exist in an area of the Kuril Islands called Whale Alley. The Makah called the gray whale “the ruler of the sea”. California’s Chumash, who believed the whale was the guardian of the sea, are not believed to have been whale hunters, eating the meat and using the bones only of beached, dead animals.
California’s Chumash, who believed the whale was the guardian of the sea, are not believed to have been whale hunters, eating the meat and using the bones only of beached, dead animals.