The Gray Whale: A Life History
Photo by Josh Withers on Unsplash
Photo by Josh Withers on Unsplash
Charles Melville Scammon, a whaling captain who hunted gray whales in Baja California beginning in the mid-1850s, was also an ardent naturalist and amateur biologist. His meticulous sketches of Pacific cetacea include some of the first detailed images of the "California gray whale." Image in public domain, courtesy of Wikimedia Commons.
The eastern North Pacific gray whale (Eschrichtius robustus), is a mid-sized baleen whale, reaching lengths nearly fifty feet and weighing up to thirty tons. Historically, gray whales were hunted intensively for their meat and oil, first by Indigenous people along the west coast of North America and the northeast coast of Eurasia and later by commercial whalers.
Early written observations of "California gray whales" were made by U.S. whalers hunting them in their calving lagoons as well as their feeding grounds in the Bering and Chukchi Seas. Whalers noted mottled gray skin scarred with barnacles and sea lice, as well as a conspicuous lack of a dorsal fin - a row of ridged bumps, known as 'knuckles,' instead protruding along the length of each individual's spine. Fragile, planked whaleboats stood little chance against the nearly ten foot wide tail flukes of adult gray whales, and logbooks from whaling voyages to Baja California are replete with accounts of the carnage caused by a single blow from the tail of an adult gray whale.
Although rarely aggressive in open water, gray whale mothers proved fiercely protective of their calves. As a crewmember of the New Haven whaler Arab observed in 1858:
[A mother gray whale's] maternal affection is so strong that she will never leave the calf unless spouting blood or else mortally wounded. The calf, having recently come into the world, is unacquainted with the danger he is in when pursued and therefore does not exert his utmost abilities to escape, or perhaps he may be so young and weak as to be unable to swim fast enough, but in either case the cow endeavors to impress the little fellow with a sense of his dangerous situation in order to help him along as fast as possible. Sometimes she assists him by lifting him along with her flukes, and takes him under one of her fins and in this manner frequently gets him along as fast as a boat can pull, but she will hardly every be more than a fathom from him, no matter what danger she may thereby place herself in.
Scientists have witnessed similar behavior in areas of killer whale predation along the migration route of eastern North Pacific gray whales. Orcas will often use natural bottlenecks and deep water to ambush migrating gray whale mothers and their calves, attacking from below and targeting juveniles. While predation is prevalent along the entirety of the migration route, attacks are particularly frequent in the Monterey Canyon just off Moss Landing, California, and in Unimak Pass, a shallow passage between Unimak and Akun islands in Alaska's Aleutian island chain. In these areas, gray whale mothers will often hoist their calves onto their stomachs, swimming upside shield them from killer whale attacks.
Gray whales are unique among baleen whales in their feeding habits, in that they forage on a wide variety of microorganisms depending on their location along their migration path. In the cold, nutrient-rich waters of the Bering and Chukchi Seas, gray whales seek out a variety of benthic (bottom-dwelling) amphipods and other invertebrates, which they suck into their mouths as they swim slowly along the sea floor. Broad “feeding pits” have been discovered in the sandy seafloor of the Bering Sea, paying testament to this method of gathering food. Sediment, gravel and debris is filtered out by the hundreds of short, cream-colored baleen plates hanging from their upper jaw, while edible organisms are trapped against the coarse baleen and consumed.
Along their migration route, however, gray whales have been observed surface feeding, filtering out and eating millions of tiny mysid shrimp in the vast coastal kelp beds of the eastern Pacific coast. Smaller populations of semi-resident whales in Puget Sound - known as the "Sounders" - feed in shallow water, targeting burrowing ghost shrimp and leaving behind deep feeding pits in the tidal flats. This generalized feeding habit – the ability to subsist on a wide variety of different food sources – has allowed gray whales to shift their feeding strategies in response to changes in prey abundance due to feeding pressures and ecological change.
Long thought to be silent, gray whales actually have a complex vocal repertoire, with a variety of calls based on context and behavior. You can click below to hear a migrating gray whale call. This variety of call, known as a conga, is a modulated frequency sweep that sounds much like its name.
This call was picked up off Vancouver Island by hydrophone array
operated by
Ocean Networks Canada, a
project based at the University of Victoria. You can find more gray
whale vocalizations, as well as blue whale songs, orca vocalizations,
and more on their Soundcloud, below.
Scientists studying gray whale vocalization in the calving lagoons of Baja California have noted that vocal behaviour is more common in these protected areas. When gray whales are migrating, they tend to vocalize much less often - likely to avoid attracting the attention of killer whales, their primary predators. In fact, when gray whales are threatened, they often hide in kelp beds or behind shoreline rocks (which help to frustrate orcas' echolocation), and fall completely silent, breathing silently with their blowholes just above the waterline in a behaviour called "snorkelling." In the relative safety of the Baja lagoons, however, gray whales have been recorded via hydrophones making up to nine discrete varieties of call. You can find recordings of the various calls heard in the calving lagoons at the Laguna San Ignacio Ecosystem Science Project's acoustic gallery.
A largely discrete gray whale population exists in the western Pacific. Now known as “western gray whales,” they number only a few hundred individuals. But the population was once much larger. Early accounts from land-based whaling stations along the western coast of Japan record these gray whales caught in significant numbers beginning in the sixteenth century. By the 1860s, US and French whalers hunting in the Sea of Okhotsk likewise noted the presence of gray whales in the western Pacific, and Japanese and Russian whaling ventures, based in imperial Joseon (Japanese-occupied Korea) and eastern Russia respectively, hunted the species in the Sea of Japan into the early twentieth century. The pressures introduced by whaling along the western gray whales’ migration route, as well as in feeding areas in the Sea of Okhotsk, resulted in rapid population decline, though not as rapid as the eastern Pacific population, which some believed was extinct by the turn of the twentieth century. When American naturalist and adventurer Roy Chapman Andrews heard rumors of "Devil-fish" sighted off the Korean city of Ulsan in 1911, he initially responded with disbelief. Visiting the city the following year, he was amazed to find Japanese colonial whaling companies landing gray whales in the western Sea of Japan. Andrews collected several specimens of whalebone from the Ulsan station, and documented his findings in his monograph, The California Gray Whale (Rhachianectes glaucus Cope)
Western gray whales appear to be genetically distinct from the main eastern Pacific population, although some admixture occurs between the two populations, particularly in northern feeding grounds. The precise location of the western gray whale’s main breeding areas is unknown, though reports of gray whales near the island of Hainan in the South China Sea indicate that these whales migrate south to the sheltered bays of the Chinese provinces of Guanxi, Guangdong, and Fujian to breed, but some scientists also speculate that they breed off the southern coast of the Korean peninsula. The population seems to frequent two main feeding grounds in the Sea of Okhotsk – one coastal area just off the northeast coast of Sakhalin Island, and another off the southeast coast of the Kamchatka peninsula. Over the past decade, Russian deepwater oil exploration off Sakhalin Island has impacted feeding areas. This population is considered at high risk of extinction.
Gray whale cows and calves slowly make their way north, hugging the coastline off Piedras Blancas in central California.
The main population of eastern Pacific gray whales undertakes an epic migration every year from the northern reaches of the Bering Sea to the calm, warm waters of Baja California. This population's migration patterns have historically been well-studied and monitored since at least the late 1950s. Yet a smaller group of some 250 gray whales, known commonly as the "Pacific Coast Feeding Group" (PCFG), terminates their northbound migration near the west coasts of Washington State and Vancouver Island. This group was first documented by Canadian marine biologist Jim Darling, and has been intensively studied in recent years by researcher John Calambokidis and his Cascadia Research Collective based in Olympia, Washington. You can find an interactive data visualization of tagged whales from the PCFG's movements for 2021, created by NOAA Fisheries, here.
"Summer resident" or "PCFG" whales have become the central focus in negotiation and dialogue around the resumption of Makah whaling off the west coast of Cape Flattery in recent years.
