Gray Whales: Characteristics, Behavior, Feeding, Reproduction

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20120522-Gray_whaleickr_-_NOAA_Photo_Library.jpgGray whales (Scientific name: Eschrichtius robustus) are mid-size baleen whales that reaches a length of 15 meters (50 feet) and a weight of 40 tons (36,290 kilograms, 36.3 tonnes). They are virtually unchanged form ancestors that lived millions of years ago. [Source: Steven L. Swartz and Mary Lou Jones, National Geographic, June 1987; Theodore Walker, National Geographic, March 1971]

The lifespan of gray whales is unknown. Estimates range from 25 to 80 years old. Mortality rates are highest for young gray whales with an average annual calf mortality of 5.4 percent. About 75 percent of first-year mortalities occur during the first two weeks after birth. Mortality records indicate that calves represent about 91 percent of deaths at winter calving grounds, followed by yearlings (0 to 19.5 percent) and adults (0 to five percent). Annual adult mortality is estimated to be between 0.1 and five percent per year. [Source: Travis Kidd, Animal Diversity Web (ADW) /=]

Eastern Pacific gray whales make the longest annual migration of any mammal on Earth, traveling about 19,000 kilometers (12,000 miles round trip between their feeding grounds between the Arctic Seas of Alaska and Siberia and their calving ground in the shallow lagoons off Baja California. . Gray whales are one of the more recognizable whale species. They can often be observed from shore during migrations and have been known to come within arm’s length of whale-watching boats.Due to their large size and feeding requirements, gray whales cannot be held in captivity.

Websites and Resources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Fishbase; Encyclopedia of Life; Smithsonian Oceans Portal ; Monterey Bay Aquarium ; MarineBio

Gray Whale History

20120522-Gray_whale blowhole 18_-_Flickr_-_NOAA_Photo_Library.jpg
Gray whale blowhole
The gray whale population is relatively healthy and strong with an estimated 20,000 whales. But it wasn’t always that way. Their pre-whaling numbers are thought to have been around 24,000. By the end of the 19th century only 2,000 or so were left. In the 1700s, whalers hunted to extinction a separate stock of gray whales in the Atlantic Ocean.

Gray whales have been hunted for thousands of years by indigenous populations along the coasts of North America and Russia. Beginning in the 1840s, commercial whalers hunted them in their breeding lagoons in Baja California and later up north. Some whalers harpooned calves in order to lure their mothers. A 19th century captain who witnessed the practice wrote, the mother whale "in her frenzy, will chase the boats, and...overturn them with her head, or dash them in pieces with a stroke of her ponderous flukes." Such behavior earned gray whales nicknames like "devil fish" and "hardhead."

Gray whales were one of the first whale species to become endangered. Their migration patterns made them very easy to hunt.Commercial whaling rapidly brought both Pacific populations to near extinction. International conservation measures were enacted in the 1930s and 1940s to protect whales from over exploitation and in the mid-1980s the International Whaling Commission instituted a moratorium on commercial whaling. [Source: NOAA]

An effort to protect gray whales began in 1937 with partial protection from whaling. In 1946, they received full protection from commercial whaling. Since then gray whales have stages a remarkable comeback. By the mid 1980s their numbers had rebounded to 18,000. In 1972, Laguna Ojo de Liebre and Laguna Guerrero Negro in Baja California were declared a whale sanctuary. In 1979, Laguna San Ignacio were added to the list. Although commercial whaling is illegal, indigenous subsistence hunting is allowed in North America and Russia. Ecotourism and whale watching are important components of local economies along gray whale migratory routes.

Kate Linthicum wrote in National Geographic,: With the rise of petroleum as lamp fuel, the establishment of the International Whaling Commission in the 1940s, and passage of the Marine Mammal Protection Act in 1972, the eastern North Pacific gray was able to bounce back. By the 1970s, foreigners were again descending on the Baja coast not to hunt whales but to admire them. Eventually the Mexican government, setting a standard for sustainable eco-tourism worldwide, stipulated that tours must be conducted by local guides, which brought new job opportunities to a region formerly dependent on commercial fishing. The whales responded with unusual friendliness, often seeking out boats on their own and prodding tourists to stroke their heads or massage their baleen. [Source: Kate Linthicum, National Geographic, April 14, 2021]

Gray Whale Habitat and Where They Are Found

Gray whale range
Gray whales are found mainly in shallow coastal waters in the North Pacific Ocean. They live in temperate, tropical and polar saltwater and marine environments typically at depths of less than 4 to 60 meters (13 to 200 feet). Gray whales feed in shallow coastal waters with muddy or sandy bottoms. They are migratory and rely on a variety of coastal habitats. During summer, they stay in waters of up to 60 meters in depth and within 0.5 kilometers to 166 kilometers of shore. [Source: Travis Kidd, Animal Diversity Web (ADW), NOAA]

There are two geographic distributions of gray whales in the North Pacific: the eastern North Pacific stock, found along the west coast of North America, and the western North Pacific stock, found along the coast of eastern Asia. U.S. federal scientists believe the eastern gray whale population is holding steady at 18,000 but the western one has only about 200 members. A third north Atlantic gray whale population existed until the 1700s and was described by whalers and colonists in North America, Iceland, Great Britain and Scandinavia. They have since become extinct in North Atlantic, likely due to over-hunting by whalers along with other human influences such as coastal development in their former calving grounds.

Most of the eastern North Pacific stock spends the summer feeding in the northern Bering and Chukchi Seas, but some gray whales have also been reported feeding along the Pacific coast during the summer, in waters off of Southeast Alaska, British Columbia, Washington, Oregon, and northern California. Eastern gray whales spend the winter in waters of less than 4 meters in depth. These waters tend to be hyper-saline and are between 15 and 20 degrees C. Winter calving grounds usually have muddy or sandy bottoms and may contain eelgrass beds or be adjacent to mangrove swamps.

Relative to eastern grays, western Pacific gray whales are poorly understood and are often referred to as the Korean, Western Pacific, or Okhotsk Sea stock. Their feeding grounds extend from the Okhotsk Sea, south along the east coast of Russia to the southern tip of south Korea. During the fall, they likely migrate to the South China Sea.

Gray Whale Physical Characteristics

Gray whale size
Gray whales range range in length from 11.1 to 15.2 meters (36.4 to 50 feet) and reach weights of 45 US tons (41,800 kilograms, 41.8 tonnes, 90,000 pounds). Females are slightly larger than males. They are between 11.7 meters and 15.2 meters (38.8 to 50 feet) while males are between 11.1 meters and 14.3 meters (36.4 to 47 feet) in length. Gray whales are endothermic (use their metabolism to generate heat and regulate body temperature independent of the temperatures around them) and homoiothermic (warm-blooded, having a constant body temperature, usually higher than the temperature of their surroundings). [Source: Travis Kidd, Animal Diversity Web (ADW) /=]

Gray whales have a mottled gray body — a trait shared among several baleen whale species — with lighter patches. They have small eyes located just above the corners of the mouth. Their pectoral flippers are broad, paddle-shaped, and pointed at the tips. Lacking a dorsal fin, they instead have a dorsal hump about two-thirds of the way back on the body, and a series of 6 to 12 small bumps, called “knuckles”, between the dorsal hump and the tail flukes. The tail flukes are nearly 10 feet wide with S-shaped trailing edges and a deep median notch. [Source: NOAA]

Gray whales often have dense infestations of parasites such as, barnacles and orange whale lice on their skin, which gives them rough and patchy appearance. They have barnacles and whale lice all over their bodies, with higher concentrations found on the head and tail. Among other baleen whales such as right whales and humpback whales the parasite concentrations are more limited to specific parts of the body. /=\

Gray whales have twin blowholes Their fluke (tail) can reach a size of three meters (ten feet) across. Individual gray whales are identified by scientists by distinctive colorings and makings on their bodies. Unlike humpback whales, with which they are commonly confused, gray whales do not have dorsal fins. The “knuckles” are of decreasing size. Gray whales have small, paddle-shaped flippers, compared to the large white flippers of humpback whales. The caudal fin has two wide, gray flukes separated by a deep notch. Their upper jaw extends past the lower jaw, and they have two to five throat pleats, which allow the mouth and throat to expand while feeding. Adults have 130 to 180 cream-colored baleen plates that are five to 25 centimeters in length. /=\

Gray Whale Behavior and Communication

gray whale

Gray whales surface to breath every four to 15 minutes. They have regular and predictable breathing patterns, exhaling three to five times from their blowhole, about 15 to 30 seconds apart. Prior to diving, they raise their tail flukes out of the water, after which they may stay submerged for as long as 15 minutes. Gray whales are said to have a particularly nasty blowhole smell. The cruise at a speed of 7.4 kilometers per hour (4.6 miles per hour) and can reach speeds of 55.5 kilometers per hour (34.5 miles per hour)

Gray whales prefer to stay close to shore. They are frequently observed traveling alone or in small, unstable groups, although large aggregations may be seen in feeding and breeding grounds. Like other baleen whales, long-term bonds between individuals are thought to be rare. [Source: NOAA]

Like many whale species, gray whales practice “spyhopping”, un which they lift their heads out of the water for several minutes at a time. Individuals may spyhop while looking for predators or fellow whales. Gray whales also “breach” (jumping into the air and splashing down on their side or back, also known as lunging or cresting), which has been interpreted as a form of communication, an attempt to remove skin parasites, and a form of play. Gray whales often feed close to shore in very shallow waters, which may lead to the appearance of an individual being stranded. [Source: Travis Kidd, Animal Diversity Web (ADW) /=]

Gray whales sense using vision, touch, sound, echolocation (emitting sound waves and sensing their reflections to determine the location of objects) and chemicals usually detected by smell. They communicate with sound and employ choruses (joint displays, usually with sounds, by individuals of the same or different species) to communicate. Gray whales emit an array of short pulses and moans. They monotonous series of high-frequency clicks are forms of echolocation used to locate objects. Most whales communicate using a variety of high and low frequency "whale songs", including prolonged deep moans. /=\

Gray Whales Feeding

Gray whale are primarily bottom feeders that consume a wide range of benthic (sea floor) and epibenthic (above the sea floor) invertebrates, such as amphipods. Gray whales suck sediment and food from the sea floor by rolling on their sides and swimming slowly along, filtering their food through 130 to 180 coarse baleen plates on each side of their upper jaw. In doing so, they often leave long trails of mud behind them and "feeding pits" in the sea floor. They have been referred to as "mussel diggers" for their bottom feeding behavior. [Source: NOAA, /=]

gray whale feeding method

Gray whales strain meals through horny baleen plates. They feed primarily on food found in the cold nutrient-rich waters of their feeding areas around Alaska and the Bering Sea. They also feed on crustaceans and plankton in waters off Mexico when the breed. They feed in shallow water with muddy or sandy bottoms or in kelp beds Sometimes they feed by swimming open mouthed into tidal currents or skimming through beds of eel grass. Scientists believe they get 95 percent of their food is from the Bering Sea.

Gray whales are the only large cetacean known to be primarily bottom feeders.. To feed, they dive to the ocean floor and fill their mouths with huge mouthfuls of mud, water and invertebrate by running the side of their mouth in the mud on the sea floor, using their tongue to create suction, and then expelling clouds of silt. Undersea photographs in the Bering Sea have revealed numerous long pits made in the sea floor that most likely were produced by feeding gray whales.

Gray whales are considered opportunistic feeders. They force sediments through their baleen plates, which trap a wide variety of crustaceans including amphipods and ghost shrimp as well as polychaete worms, herring eggs and various forms of larvae. Food items are scraped off baleen plates with their large tongue and ingested. Gray whales use group feeding strategies on schools of small fish during their southern migration. During feeding episodes, three to four whales corral a school of fish, as a single whale swims up through the school with its mouth agape. The head of the feeding whale emerges out of the water and remains in this position for up to a few minutes. Each whale in the group repeats this process until the school of fish has been significantly depleted. [Source: Travis Kidd, Animal Diversity Web (ADW) /=]

Gray Whale Migrations

Gray whales have one of the longest migrations of any mammal species, traveling from 16,000 to 22,530 kilometers (10,000 to 14,000 miles) per year. During migration, they swim at a steady speed of 4.8 to 9.6 kilometers per hour (three to six miles per hour). .

In the fall, gray whales migrate from their summer ground in the Bering Sea, Chukchi Sea north of Alaska and Siberia up to 8.000 kilometers (5,000 miles) along the Pacific coast to Mexico between October and February They spend the winter in Baja California, mating, calving and rearing their young, and migrate back to Arctic waters between late January and early May. Some whales return to the same small lagoons on Mexico in the breeding season. Others move among different lagoons.

gray whale east Pacific migration route

Calves are born during migration or in the shallow lagoons and bays of Mexico from early January to mid-February. From mid-February to May, eastern North Pacific gray whales can be seen migrating northward along the U.S. west coast. Photo-identification studies indicate that gray whales in this stock move widely within and between areas on the Pacific coast. They are not always observed in the same area each year, and there may be gaps of several years between repeat sightings. Although western and eastern DPS gray were thought to be relatively isolated from each other, recent satellite tagging data have shown that at least some western North Pacific DPS gray whales migrate across the northern Gulf of Alaska, and along the west coast of British Columbia, the United States, and Mexico. [Source: NOAA]

Off coast of Baja California, four specific locations have been identified as important calving grounds for eastern gray whales: 1) Laguna Ojo de Liebre, 2) Guerrero Negro, 3) Bahia Magdalena, and 4) Laguna San Ignacio. Eastern gray whales are often seen during migration, off the western shores of the United States and British Colombia. During the return migration in the spring, a small population of about 80 individuals remains in more southerly Canadian waters. [Source: Travis Kidd, Animal Diversity Web (ADW) /=]

The western Pacific gray whales' feeding grounds extend from the Okhotsk Sea, south along the east coast of Russia to the southern tip of south Korea. During the fall, they likely migrate to the South China Sea to give birth to young in sheltered lagoons and bays along the southern Chinese coast. However, this has not been well documented. /=\

There are around 17,500 gray whales that migrate along the west coast of the Americas. Their numbers are regarded as healthy. But that in not the case with their Asian-Russian cousins on the other side of the Pacific, who spend their summers of the coast of the Russian Far East and their winters in the South China Sea. About 100 or so gray whales feed during the summer off of Sakhalin island, near where large foreign energy companies are drilling for oil and gas. There are worries that the whales could be harmed by collisions with boats or contamination of their feeding areas by an oil spill. The use of explosives in seismic testing appears to disturb them and drive them from the area. There are plans to put pipeline and offshore platforms right in the middle of their feeding areas. The oil companies are planning to limit construction while the whales are feeding and other measures. [Source: NOAA]

Rare Western Gray Whale Swim Eastern Gray Whale Routes

20120522-Gray_whale bb.jpg In the winter of 2010-2011, scientists tracking a rare western Pacific gray whale were to find that when the whales left the Asian coast they crossed the Bering Sea and swam south along Alaska, British Columbia and the Pacific Northwest coasts instead of towards the South China Sea. A science team coordinated by the International Whaling Commission had attached satellite tags to several of the western gray whales. according to an announcement by Oregon State University, which is taking part in the study. [Source: Dan Joling, Associated Press, September 19, 2011]

Associated Press reported: Only about 130 western Pacific gray whales remain and little is known of their winter habits. They spend summers near Russia's Sahkalin Island. In October 2010, researchers limited by foul weather placed only one cigar-size satellite tag on a whale on the last day of field work. The 13-year-old male dubbed "Flex" spent more than two months feeding near Sakhalin Island before moving across the Sea of Okhotsk to the west coast of the Kamchatka Peninsula. In January 2011 to the surprise of researchers, it began swimming steadily east across the Bering Sea. Eighty miles north of Alaska's Pribilof Islands, the whale turned south, and swam between Aleutian Islands into the Gulf of Alaska. It continued southeast to shallow coastal waters off Washington and Oregon. Its last confirmed location was Feb. 4 off Siletz Bay, Ore., where researchers believe the satellite tag fell off. The whale had traveled 5,335 miles over 124 days.

Bruce Mate, director of the Marine Mammal Institute at Oregon State University, told The Associated Press in January that little was known about the winter habits of western Pacific gray whales. One hypothesis was that they swam south down the Asian coast to the southeast China Sea. Tracking one to North America waters was "surprising everybody," he said. Marine researchers later determined that Flex had crossed the Pacific at least once before. Researchers sent a photo of Flex to Cascadia Research Collective, a scientific and education organization based in Olympia, Wash., which matched the photo to a whale photographed in 2008 off Canada's Vancouver Island.

Gray Whale Mating and Reproduction

Gray whales are viviparous, meaning they give birth to live young that developed in the body of the mother. They engage in seasonal breeding and year-round breeding. The breeding season is every year or every other year. Most often conceptions occurs in late November to early December. The number of offspring is usually one. One occurrence of twin fetuses was reported in 1987. The gestation period ranges from 13 to 14 months.The weaning age ranges from six to seven months and the average time to independence is unknown years. Females and males reach sexual maturity at six to 12 years.[Source: Travis Kidd, Animal Diversity Web (ADW) /=]

Gray whales have a high reproductive rate, relative to other baleen whales. They are polygynandrous (promiscuous), with both males and females having multiple partners. Males have two-meter (six-foot) -long penises. Females roll on their side to show they are receptive. Sometimes there are huge orgies that last for hours involving 18 to 20 individuals, with a several females mating with multiple partners. Group mating events of three or more individual have been documented. The fathers are probably unknown. In breeding areas males often outnumber females two to one. Each season about a hundred cows and calves find refuge from aggressive males in San Ignacio Lagoon.

Gray whales become sexually mature at an average of about eight to nine years old. Females gray whales often begin mating at age six and calve every season. Studies suggest that size may be a better indicator of sexual maturity than age. Males average 11.1 meters in length at time of sexual maturation and females average 11.7 meters. Sixty percent of the population consists of sexually mature adults. The average generation length (number of years between an individual's birth and the age at which they give birth) for gray whales is 22 years. /=\

Gray Whale Calves

Gray whale young are precocial. This means they are relatively well-developed when born. Parental care, and pre-birth provisioning is provided by females. During the pre-weaning and pre-independence stages provisioning and protecting are done by females.Calves are typically born dark gray and lighten as they age to brownish-gray or light gray. Gray whales inherit their mother's feeding grounds and are often seen, one year after they become independent, in their mother's feeding grounds. [Source: Travis Kidd, Animal Diversity Web (ADW) /=]

At birth they measure 14 to 16 feet (4.3 to 4.9 meters) in length and weigh between 680 and 907 kilograms (1,500 and 2,000 pounds). They are nurses for six to seven months on milk that is 53 percent fat, among the richest in the world, and grow quickly. By the end of winter they are 1.2 meters (four feet) longer and have doubled their weight to two US tons. Before the migration, calves train by swimming into oncoming currents. As they become more confident they leave their mothers for periods of time and play with things like kelp.

In the upper San Ignacio Lagoon most gray whale females give birth in the relatively shallow water, averaging about five meters (16 feet) in depth. Mothers with calves prefer to stay separate from mating and courting males and females. "Play groups" of up to a dozen mother and calve pairs bond with one another by touching, rubbing, rolling and blasting each other with bubbles. They even teach young whales what to do if they are beached.

Gray whale cows often hold newborn calves to the surface to help them breathe and are fiercely defensive of their young, especially against potential predators such as orcas and human whalers. Historical accounts of whalers who attempted to exploit their calving lagoons, frequently referred to cows as "Devilfish". Gray whales replenish fat reserves during the summer. Pregnant females are especially dependent on these reserves. From the time they leave the summer feeding grounds in the fall, to when they return in early summer, females rely on fat reserves for energy and milk production. During times of limited food availability, interval between individual calving events may be extended.

Eastern gray whale calves are born in late January in the warm coastal waters of Baja California, Mexico; however, early calving during the fall migration has been documented. Western gray whales are believed to have winter calving grounds along the coast of the South China Sea and likely have calving patterns similar to those of eastern gray whale. Calving grounds are typically in shallow lagoons that are less than four meters in depth and are hyper-saline.

Image Source: Wikimedia Commons, NOAA, migration map: San Luis Obispo County Office of Education

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated May 2023

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