Gray whales

(Eschrichtiidae)

Class Mammalia

Order Cetacea

Suborder Mysticeti

Family Eschrichtiidae

Thumbnail description
Medium-sized, bottom-feeding baleen whales with black or slate-gray skin, much blotched, mottled and encrusted with barnacles; gray whales are distinguished by their short, coarse baleen plates and by having a dorsal ridge instead of a dorsal fin

Size
43–46 ft (13–14.1 m); 44,000–81,500 lb (20,000–37,000 kg)

Number of genera, species
1 genus; 1 species

Habitat
Shallow coastal waters

Conservation status
Lower Risk/Conservation Dependent

Distribution
Extant populations migrate seasonally between Arctic and warm temperate waters of the North Pacific; western population summers in the Sea of Okhotsk and winters off the coasts of South Korea and Japan; eastern population summers in the Bering, Chukchi, and Beaufort Seas off northeastern Alaska, then migrates south along the west coast of North America to winter on calving and breeding grounds in coastal Baja California and western Mexico

Evolution and systematics

The gray whale, Eschrichtius robustus, is the only species in the family Eschrichtiidae (formerly Rhachianectidae). Escrichtidae is one of four families in the suborder Mysticeti (the other three are Balaenidae, the right whales; Neobalaenidae, the pygmy right whale; and Balaenopteridae, the rorquals). Of these groups, Eschrichtiidae is considered to be the most primitive. Evidence suggests that gray whales, rorquals, and right whales diverged from a common ancestor during the Miocene (26 to 7 million years ago). Concerning the fossil record, only a single fossil gray whale specimen, dating to the Pleistocene (50,000 to 120,000 years ago) has been found in southern California.

The taxonomy for this species is Eschrichtius robustus (Lilljeborg, 1861), Sweden. Other common names include: English: devil-fish, desert whale, the friendly whale; French: Baleine grise; Spanish: Ballenna gris.

Physical characteristics

Although they are called "gray," these whales are actually black—at least, they are at birth. The skin color changes with time, primarily because of scarring caused by barnacles. These sedentary marine crustaceans attach to whale skin after it has been scraped during feeding bouts; they mostly cluster on the head but may occur anywhere on the body. A large whale may carry hundreds of pounds of barnacles. Although scarring is what changes the skin color, the presence of so many barnacles and also sea lice (orange or yellow in color and which also routinely infest gray whales) contributes to a gray whale's overall light, mottled appearance.

Gray whales have been described as "living fossils" and as "the most primitive of the great whales" (Nollman 1999) because of their short, coarse baleen plates and their lack of a dorsal fin. On the back, toward the tail, where most other baleen whales have a dorsal fin, gray whales have a series of 8 to 14 bumps that form a "dorsal ridge". The short baleen plates are less than 20 in (50 cm) long (compare this to bow-head whales, which have the longest baleen, 14 ft [4.3 m] long). The plates are ivory to yellow in color; thicker than the baleen plates of other baleen whales; and arranged in two groups of 130 to 180 plates each on either side of the mouth; the two rows of baleen plates do not meet at the front of the mouth, as they do in members of the closely related family Balaenopteridae. The mouth itself is slightly arched and the outside of the jaw is studded with small, sensitive hairs. Gray whales have two or three (rarely four) shallow furrows on their throats; these "throat pleats" are shorter and less numerous

than those of many other baleen whales (for example, Bryde's whales have as many as 70).

Baleen whales as a group include large species and small; the largest living animal on earth, the blue whale (Balaenoptera musculus), is 90 ft (27.5 m) long, whereas the minke whale measures a mere 25–30 ft (7.9 m). Compared to these relatives, gray whales are considered medium-sized. Adult females average 46 ft (14 m) in length with an average weight of almost 70,000 lb (32,000 kg); adult males are somewhat smaller than females, averaging 43 ft (13 m) in length. Gray whales are comparatively slender for their size, with narrow heads that are small in relation to the total body length. The pelvis is relatively large, however.

Other distinguishing traits include two blowholes; 56 vertebrae (with the neck vertebrae being separate, not fused); and flippers with only four digits (the first finger [thumb] is absent; some baleen whales have five digits in the flippers). Male gray whales have very large testes for their body size, and are assumed to produce large volumes of sperm.

Distribution

Historically, gray whales occurred both in the North Atlantic and North Pacific basins; however Atlantic populations were extinct by the mid-1700s due to whaling. The eastern Atlantic population is thought to have spent the summer in the Baltic Sea and wintered off the Atlantic and Mediterranean coasts of southern Europe and also North Africa. The western Atlantic population of gray whales may also have summered in the Baltic sea; this population migrated south along the eastern coast of North America to breed and bear young in shallow lagoons and bays off southeastern Florida.

The Pacific basin continues to support two genetically distinct gray whale populations, one in the western Pacific and one in the eastern Pacific. Members of the eastern population spend the summer on feeding grounds in the Bering, Beaufort, and Chukchi Seas between northern Alaska and Siberia (although some whales do feed farther south in summer, off the coasts of southeast Alaska, British Columbia, Washington, Oregon, and California). Starting in October and continuing through January, whales in the Arctic move south along the east side of the Bering Sea and through Unimak Pass in the Aleutian Islands, then continue down the western coast of North America. By January or February a significant portion of the population has arrived at breeding and calving grounds in warm, shallow, nearly landlocked lagoons and bays along the west coast of Baja California and the eastern side of the Gulf of California in western Mexico. (Some members of the population do pass the winter farther north along the coast.)

Members of the western or Korean gray whale population are thought to spend summer months feeding in the sea of Okhotsk and then move south to breed in winter somewhere along the coast of southern Korea or Japan. (A western population that bred in the Inland Sea of Japan was extinct by the

beginning of the twentieth century; a population that bred off southern Korea was all but wiped out by the 1930s.)

Habitat

Gray whales are notable for their habit of migrating and feeding in very shallow water; they are typically found closer to shore than any other large whale—usually within 1.9 to 3.1 mi (3–5 km) of land.

This species is sometimes referred to as "the desert whale" because it leaves the open sea to breed and calve in shallow desert lagoons—the only whale to do this routinely. As of 2003, the gray whales' most important winter breeding habitat consisted of just four areas on the coast of Baja California: Guerrero Negro Lagoon, Scammon's Lagoon, San Ignacio Lagoon, and Magdalena Bay.

Behavior

Gray whales make the longest known migration of any whale—and indeed of any mammal. Members of the eastern Pacific population travel as much as 10,000–12,000 mi (16,000– 19,300 km) round-trip each year. In contrast to their relatives, the humpbacks and blue whales, which migrate across the open ocean, gray whales migrate exclusively in coastal waters.

Gray whales swim slowly, averaging 4.4–5.6 mph (7–9 km/hr), but can speed up to 8 mph (13 km/hr) when pursued. The "spout" or "blow" (exhalation) is described as low and spreading; it rises only about 118 in or about 10 ft (300 cm) above the ocean surface (in comparison, the blow of a blue whale rises more than twice as high).

Swimming whales follow a characteristic pattern; they make a series of short surface dives followed by a longer, deeper dive; observers will see three to five blows, 30 to 50 seconds apart, followed by a dive that typically lasts for 4 to 5 minutes; the whale blows three to five times when it surfaces. Gray whales do not arch their backs before diving the way humpbacks (Megaptera novaeangliae) do; their tail flukes rise above the surface of the water at the start of a deep dive but not a shallow one. The deepest documented dive by a gray whale was to a depth of 248 ft (75.6 m). To put this in context, sperm whales—the deepest-diving whales—are known to reach depths of 6,560 ft (2,000 m) when they feed.

Whales on migration dive to shallower depths than do feeding whales. Diving whales sometimes engage in a behavior

called "bubble-blasting" —they submerge, then release air underwater, so that it bubbles to the surface. It is not clear whether this behavior is a stress response or a mechanism for regulating buoyancy.

Although female gray whales accompany their calves on the northward migration, migrating gray whales do not otherwise appear to travel in family groups. Whales on migration may swim alone, in groups of two or three, or in pods of up to 16 animals; a typical migration group has about nine animals. The composition of these groups is not stable; instead the group make-up changes constantly (shifting social alliances are typical of baleen whales).

Of all migrating gray whales, female whales and their calves often swim the farthest. On their northward migration, they continue past the Bering Sea—where the majority of gray whales congregate to feed—until they reach the Chukchi Sea. Here, food may not be quite so abundant, but neither are predatory killer whales, or orcas (Orcinus orca).

Gray whales seem to be able to detect their orca enemies from a distance, by their vocalizations. In one study conducted along the coast of California, researchers broadcast killer whale vocalizations underwater; migrating gray whales avoided the sounds by rapidly changing course, swimming toward shore, and moving into concealing beds of kelp. Females with calves defend their young fiercely—not just from killer whales but from any perceived threat. This behavior caused nineteenth-century whalers working the breeding lagoons off Baja California to give gray whales the nickname of "devilfish." They were described as "a cross between a sea-serpent and an alligator," as American whaleboat captain Charles Scammon wrote in his landmark 1874 book on whale behavior, adding, "The casualties from coast and kelp whaling are nothing to be compared with the accidents that have been experienced by those engaged in taking the females in the lagoons. Hardly a day passes but that there is upsetting or staving of boats, the crews receiving bruises, cuts, and, in many instances having limbs broken; and repeated accidents have happened in which men have been instantly killed, or received mortal injury."

Though fierce when threatened, gray whales that feel secure will allow humans to approach remarkably close. Since the latter half of the twentieth century, whale-watching has been a popular activity in the lagoons of Baja California. In 1975, tour operators first noticed that some whales would actually approach whale-watch boats and allow themselves to be petted. This behavior has earned them a new nickname: "the friendly whale."

Gray whales display such common cetacean behaviors as breaching (in which the whale leaps above the water's surface, then falls back into the water, landing on its back or side) and spy-hopping (positioning the body vertically in the water, with the head raised above the sea surface, sometimes while turning slowly). Gray whales rarely breach outside of their southern breeding lagoons, however, leading some researchers to hypothesize that this behavior is a component of courtship. Alternately, breaching may represent an effort to get rid of itchy parasites, or it may be an expression of stress, or a form of play. The function of spy-hopping also is not known. One idea is that it helps whales to orient while on migration; however whales sometimes spyhop while allowing their eyes to remain underwater.

Among the baleen whales, humpback whales are known for their long, complex courtship songs. Gray whales do not make such sustained or complex vocalizations. Most vocalizations are at a frequency range of less than 1500 Hz. Researchers have described several types of calls, including "pulses" that sound like clangs, pops, and croaks; low-frequency "moans" that, to human ears, sound like a cow mooing; "rapid upsweeps"; and grunting and groaning sounds, like a zipper being pulled open. Bubble blats and bubble trails are also categorized as vocalizations. Field observations suggest females use pulses to communicate with their calves.

Feeding ecology and diet

Like all mysticete whales, gray whales use their comb-like baleen plates the way humans use a tea-strainer or colander—to collect small food items from the water. Most baleen whales strain free-floating plankton out of the water column, and gray whales are capable of doing this too—but usually, they take their prey from the sea floor. A feeding whale dives to the bottom, rolls onto its side—usually the right side—then shoves its body forward and upward, taking in a mouthful of soft sediment and water. Then, with its large, muscular tongue—which is the size of a compact car—the whale pushes the muddy mouthful forward against its baleen. Mud and water filter through, leaving edible components caught against the baleen strands. This unusual bottom-feeding behavior

earned gray whales the nicknames of "hard head" and "mud digger" from nineteenth-century whalers.

Amphipods make up the major part of a gray whale's diet. These small crustaceans, which are related to shrimp, live in burrows on the ocean floor. Amphipods are particularly plentiful in the cold waters off the northern Pacific Coast, where whales spend the summer; a single species, Ampelisca macrocephala, can account for 95% of the whales' intake on their Arctic feeding grounds. Gray whales do eat various other small, bottom-dwelling invertebrates, however, including clams, crabs, and marine worms; a study of whales feeding in Clayquot Sound, British Columbia, documented mysid shrimp, pelagic porcelain crab larvae, and benthic ghost shrimp as part of the diet. Other studies of gut contents reveal that gray whales sometimes consume small fish, as well as kelp and other marine vegetation; however it is not clear whether the whales eat algae on purpose or accidentally, simply because it happens to be growing on the bottom.

Gray whales do most of their feeding between May and November, while they are in Arctic waters. This means the insides of their mouths are constantly exposed to freezing water; however a network of blood vessels at the base of the tongue functions as a highly effective countercurrent exchange mechanism to reduce the loss of body heat. In one study, scientists measuring heat loss by a captive gray whale calf were surprised to discover that the animal lost more heat through the thick, insulating layer of blubber covering its entire body than it did through its tongue.

A lone adult whale may eat as much as 65 tons (59 tonnes) of food per year—except that feeding is not spread out over an entire year but is concentrated in the five months spent on the summer feeding grounds in the Arctic. The whales accumulate a thick layer of blubber during the summer, then eat very little on migration and while at the breeding lagoons, living off the stored energy in their blubber. Pregnant female whales store enough calories that they can make the long southward migration, give birth, nurse a calf, and swim north again—all while fasting.

Reproductive biology

Gray whales are one of the three species of baleen whales (right whales [Eubalaena spp.] and humpback whales are the other two) that form "breeding aggregations," in other words, gather in large numbers to mate and give birth. The other eight mysticete species do not gather to breed.

Gray whales use different habitats for mating than for calving. Mating typically occurs at the entrances to the lagoons, or just outside (although courtship and mating can also occur while on migration); while this frenzied courtship goes on outside, the females and their calves stay well inside the lagoons. Although gray whales are not particularly social, there are some reports of whales supporting laboring females or injured animals so they can stay at the surface and breathe.

Courting gray whales are very active; they can be seen rolling and breaching and swimming in line. These whales are not monogamous; observations suggest each female probably mates with a number of different males. This, along with the fact that males have large testes and produce large amounts of sperm, suggests that sperm competition occurs.

Gray whales are sexually mature at the age of six to eight years; however the average age of females when they first give birth is nine years. The breeding cycle takes two years, with gestation lasting for 13.5 months of that period. Pregnant females are the first members of the population to leave the breeding lagoons; they depart in mid-February. During the more than year-long gestation period, females make the long trip north to the feeding grounds and then back to the breeding lagoons.

Most gray whale calves are born in the Baja lagoons between early January and mid-February (a few newborn calves have been also sighted along the California coast, suggesting that some births occur outside of the lagoons). A typical newborn calf may be 15 ft (4.6 m) long and weigh about 1,100 lb (500 kg). It drinks 50 gallons of milk (190 l) a day and grows rapidly. By the end of winter most calves reach a length of 18–19 ft (5.5–6 m).

If pregnant females leave the breeding lagoons early, mothers with calves are the last to leave, sometimes heading north as late as May or June. By spending the maximum possible amount of time in protected habitat, they give their calves

time to grow large enough and strong enough to evade killer whales on the trip north. (Killer whales will not enter the shallow lagoons.) Like most female baleen whales, gray whales nurse their calves for about six to seven months. This means the calves are nursing throughout the northbound migration. They are weaned in late summer, on the Arctic feeding grounds where food is plentiful. Maximum longevity is reported at 70 years.

Conservation status

The eastern population of Atlantic gray whales is thought to have become extinct as early as a.d. 500; the western Atlantic population, which migrated seasonally along the eastern coast of North America, became extinct in the eighteenth century. As of 2003, the western Pacific or Korean population of gray whales is critically endangered, with fewer than 100 individuals remaining.

In contrast to these sad stories of extinction, the eastern Pacific population of gray whales represents one of the few success stories in whale conservation—indeed in the conservation of any endangered species. The exploitation that came with the European settlement of North America led to near-extinction of the eastern Pacific population by the middle of the twentieth century, but the species made a remarkable and rapid recovery once it was protected, with populations returning to pre-exploitation levels by the mid-1990s. In 1946, the International Whaling Commission banned the commercial take of gray whales; they were later additionally protected under the U. S. Endangered Species Act in 1973. With these protections gray whales made a remarkable recovery. In 1994, when the population numbered about 22,000 individuals, the U. S. Fish and Wildlife Service removed the gray whale from the U. S. Endangered species list. Experts hypothesize that the gray whale's habit of forming breeding aggregations helped the species to make this remarkable recovery; in species that breed solitarily, such as blue whales, it's thought that individuals have a hard time finding a mate when populations are very small.

The western Pacific population of gray whales does remain very small, despite having been protected at the same time as the eastern population. The probable reason this population failed to recover was that illegal whaling continued. The World Conservation Union (IUCN) listed the western gray whale as Critically Endangered in 2000.

Habitat quality is of concern. The Mexican government and Mitsubishi Corporation have proposed joint development of a salt-production facility in San Ignacio Lagoon, which is

one of the whales' key calving grounds. However experience suggests the noise and activity associated with this development would be harmful to the whales; when dredging for a salt works was conducted in Guerrero Negro Lagoon for several years, breeding whales deserted it. As of 2003, a coalition of Mexican and U. S. environmental groups has been able to prevent development in San Ignacio.

As whale populations have rebounded, animals have started to move back into the waters around such major cities as San Diego, San Francisco, and Seattle, where they historically occurred, and this has led to more concerns; decades of industrial discharge, discharge from sewage treatment facilities, and agricultural runoff have left the sediments in these coastal areas highly polluted—a potential problem for a bottom-feeding whale that wallows in sediment. Offshore oil exploration and oil production are other issues. In controlled experiments, gray whales actively avoided the noise from these activities and, as a result, sometimes moved into very shallow water, risking stranding.

Even though gray whales were removed from the Endangered Species list in 1994, researchers have continued to monitor populations. A significant increase in gray whale strandings was noted in 1999 and 2000. The population estimate in 2001–2002 was 17,500 individuals—significantly down from a high of 26,635 in 1997–98; however, researchers estimate the total carrying capacity for the western Pacific at 20,000 to 24,000 whales and say the most recent decline is probably within normal fluctuation parameters—and possibly due to a natural climate cycle that has temporarily put food in short supply. Population monitoring continues.

Significance to humans

Indigenous peoples of northwestern North American and eastern Siberia hunted gray whales for oil, meat, hide, and baleen for hundreds if not thousands of years; indeed, indigenous whaling was the major economic activity along the Chukchi, Bering, and Okhotsk seas before Europeans came on the scene and began taking large numbers of whales.

Indigenous peoples of Europe and Japan probably hunted gray whales as well. The indigenous peoples of eastern North America and Baja California are not thought to have hunted the whales, but evidence shows they did take advantage of stranded whales as a source of food and other materials. Images of gray whales can easily be identified in cave and rock paintings made by indigenous people northeast of San Ignacio Lagoon.

In Baja California, Magdelena Bay was the center of American whaling from 1845 to 1874. In the United States and Europe at this time, whale oil was a valuable commodity, burned in lamps for household illumination and used to lubricate machinery.

With the recovery of eastern Pacific populations, whale watching has replaced whaling as a major money-making industry in Baja California and along North America's West Coast. Millions of people watch these whales on migration each year. Magdelena Bay has sponsored a major gray whale festival since 1994.

Resources

Books

Dedina, Serge. Saving the Gray Whale: People, Politics, and Conservation in Baja California. Tucson: University of Arizona Press, 2000.

Mann, Janet, Richard C. Connor, Peter L. Tyack, and Hal Whitehead. Cetacean Societies: Field Studies of Dolphins and Whales. Chicago: University of Chicago Press, 2000.

Mead, James G. Whales and Dolphins in Question. Washington, DC: The Smithsonian Institution, 2002.

Nollman, Jim. The Charged Border: Where Whales and Humans Meet. New York: Henry Holt and Company, 1999.

Simmons, Mark P., and Judith D. Hutchinson. The Conservation of Whales and Dolphins: Science and Practice. New York: John Wiley & Sons, 1996.

Periodicals

Buckland, S. T., and J. M. Breiwick. "Estimated Trends of Eastern Pacific Gray Whales from Shore Counts (1967/68 to 1995/96)." Journal of Cetacean Research and Management 4, no. 1 (2002): 41–48.

Dunham, Jason S., and David A. Duffus. "Foraging Patterns of Gray Whales in Central Clayquot Sound, British Columbia, Canada." Marine Ecology Progress Series 223 (2001): 299–310.

Heyning, John E. "Thermoregulation in Feeding Baleen Whales: Morphological and Physiological Evidence." Aquatic Mammals 27, no. 3 (2001): 284–288.

Moore, Sue E., and Janet T. Clarke. "Potential Impact of Offshore Human Activities on Gray Whales (Eschrichtius robustus)." Journal of Cetacean Research and Management 4, no. 1 (2002): 19–25.

Weller, David W., Alexander M. Burdin, Bernd Wursig, Barbara L. Taylor, and Robert L. Brownell, Jr. "The Western Gray Whale: A Review of Past Exploitation, Current Status, and Potential Threats." Journal of Cetacean Research and Management 4, no. 1 (2002): 7–12.

Wolff, Wim J. "The South-eastern North Sea: Losses of Vertebrate Fauna During the Past 2000 Years." Biological Conservation 95, no. 2 (2000): 209–217.

Other

Gray Whales (Eschrictius robustus): Eastern North Pacific Stock. National Marine Fisheries Service. December 10, 2000. <http://www.nmfs.noaa.gov.prot_res/PR2/Stock_Assessment_Program/Cetaceans/Gray_Whale_(Eastern_N._Pacific)/AK00graywhale_E.N.Pacific.pdf>.

Cynthia Berger, MS