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Grey Whales

About AquaFacts: AquaFacts are a resource for students who are looking for information on the animals at the Aquarium or other Aquarium-related topics. Here, we’ve compiled some of the most frequently asked questions that we’ve received about grey whales. The answers come from our biologists and from reputable sources that we reference at the end of this page. If you have a question about grey whales that’s not addressed in this page or the references below, please feel free to email our librarian.

Grey Whale

Questions & Answers

How big are grey whales?

An adult male grey whale can grow to 14.6 m in length—longer than a city bus. Females are slightly bigger than males, and both males and females weigh up to 30,000 kg.

What do grey whales eat?

These enormous animals eat large quantities of tiny animals. Scientists believe an adult grey whale consumes an average of about 1,100 kg of food per day. The main component of their diet is small, shrimp-like animals called amphipods that live on muddy ocean floors. Amphipods are minute compared to grey whales. Grey whales also eat tubeworms, mysids (another shrimp-like animal), small fishes, ghost shrimps, herring eggs and crab larvae (especially larvae of porcelain crabs), which are a seasonally important food source for them in British Columbia.

How do grey whales eat?

Grey whales use suction to draw food into their mouths. A feeding grey whale turns so that one side of its mouth faces the ocean bottom. The whale opens its mouth slightly and pulls in its huge tongue. This draws in sediment and amphipods from the ocean bottom. The whale then pushes the sediment through the baleen plates on the opposite side of its mouth. The amphipods are caught in the baleen, which acts like a filter. 

Grey whales are the only baleen (filter feeder) whale that regularly feeds on bottom-dwelling animals. Scientists think they can tell whether a grey whale is a right or left-handed feeder by looking at the barnacles and scraped skin on its head. There are more skin scratches, and fewer barnacles, on the side of the whale that faces the bottom when it feeds. Sometimes grey whales use other feeding techniques such as surface skimming for crab larvae.

Do grey whale migrate?

Grey whales have the longest migration route of any mammal. Each year they cover more than 9,000 km travelling between their summer feeding areas in Alaska and the Bering Sea, and their winter breeding lagoons in Baja California and Mexico. Migrating grey whales travel 60 to 80 km each day, often close enough to shore that they can be sighted from land. They navigate by following the contours of the sea floor. Some grey whales spend their summers in B.C. instead of travelling further north; this group is known as the summer-resident grey whales.

Where do grey whales live?

Winter Breeding
Grey whales spend winters, from January to March, in the warm waters of Baja California, Mexico, where pregnant females give birth. By late February, they start swimming northward. Adult males, newly-pregnant females and juveniles leave first, followed by females and their calves. Some grey whales start feeding when they reach the waters along Vancouver Island, although in some years, some start feeding as far south as central California. 

Summer Feasting
During the summer months, most grey whales feed in the Bering Sea, the Chukchi Sea, the western Beaufort Sea and the Arctic Ocean. Here they gorge themselves on massive quantities of food! Grey whales rely almost entirely on their fat reserves as an energy source during their winters and migrations so they build up their blubber and other fat reserves by feasting through the summer months. They gain 16 to 30 percent of their body weight during this time. In October, as the northern winter begins, pregnant females lead the procession of migrating grey whales returning to the warmer waters of Baja California.

Where can I see grey whales?

Each spring, thousands of people flock to Pacific Rim National Park on Vancouver Island hoping to catch a glimpse of migrating grey whales heading up to their summer feeding grounds. Since the whales often travel close to the shoreline, many park visitors spot the whales from the beach! There are summer residents that can be observed all through the summer off the Pacific Rim National Park. West Coast whale watching companies use small boats to bring people closer. Guidelines help ensure that these boats do not interrupt or disturb the whales. For more information about whale watching, phone the Tourism Association of Vancouver Island at 250-382-3551.

Were grey whales ever hunted?

Historically, grey whales were hunted by the Chukotka people of the US/Russian Arctic, as well as many coastal First Nations in B.C. and Washington. Grey whales were hunted commercially for their meat and oil by European, Japanese, and North American whalers, especially in the 17th and 18th century. Relentlessly hunted for their meat and oil, Atlantic grey whales became extinct in the 18th century. The eastern North Pacific population also plummeted but has since made a dramatic comeback.

Are grey whales still hunted today?

Not commercially; in the late 1940s, a convention under the International Whaling Commission (IWC) prohibited the commercial whaling of grey whales. These restrictions enabled grey whales to make a dramatic comeback to current population levels. However, subsistence hunting still occurs in Russia and the US Arctic.  The Makah tribe of Washington State is also negotiating the right to hunt grey whales for subsistence purposes.

What is the future of grey whales?

The latest shore-based count in 2005 showed the population at 18,000 animals, down from 26,600 in 1998. The grey whale populations is likely to remain around this number, unless there is a change in the ocean ecosystem, because it is currently thought that it has reached carrying capacity. This means the number of grey whales is as high as the North Pacific Ocean can support. The number of western North Pacific (Korean) grey whales is very low—100 to 200 whales. They are listed as critically endangered.

How can I help?

If you see a whale or dolphin off the coast of British Columbia, we would love to hear about it. Report your sighting at www.wildwhales.org

Facts & References

Key Facts

  • Sexual maturity: 5-11 years old, or when they reach 11-12 m in length.
  • Length of pregnancy (gestation period): 13-14 months.
  • Calf size: a 4.5 m long newborn grey whale weighs roughly 450 kg!
  • Calving: every two years on average. Females give birth to a single calf; mating and calving occur primarily in the lagoons of Baja California, Mexico; calves nurse for about eight months on milk containing 53 percent fat—human milk, by comparison, is only two percent fat.
  • When the calves are weaned, they begin using their baleen to sieve food from the water.

Did You Know?

  • Grey whales are covered with skin parasites! Whale lice and barnacles both hitch a free ride
  • Whale lice are parasites that eat whale skin and damaged tissue. Barnacles eat plankton and food scraps
  • Grey whales are often seen breaching; leaping into the air and splashing back into the water. It’s thought that breaching helps grey whales dislodge some of the parasites clinging to their skin.
  • Grey whales have from 130 to 180 baleen plates hanging from their upper jaw. These plates measure from 5 -25 cm in length and are made of keratin—the same material as our fingernails.
  • Migrating grey whales have a predictable breathing pattern: a whale will blow 3-5 times, raise its flukes, then submerge for 3-5 minutes. It can stay submerged for up to about 15 minutes
  • Early whalers nicknamed grey whales “devil fish” because of their defensive behaviour in calving lagoons
  • Some killer whales attack grey whales. Many grey whales sport killer whale teeth scars on their tail flukes. Transient killer whales are a significant source of mortality for grey whale calves on their first migration. Aquarium senior marine mammal researcher Dr Lance Barrett-Lennard has found that transient killer whales in False Pass, Alaska, kill 100-150 juvenile grey whales a year.


  1. American Cetacean Society. 2007. Grey Whale Fact Sheet
  2. Busch, Robert H. 1998. Grey Whales: Wandering Giants. Custer, WA: Orca Publishing.
  3. Gordon, David G., and Alan Baldridge. 1991. Grey Whales. Monterey Bay, CA: Monterey Bay Aquarium.
  4. Leatherwood, Stephen and Randall R. Reeves. 1992. The Sierra Handbook of Whales and Dolphins. San Francisco: Sierra Club Books.
  5. Jones, Mary Lou, Steven L. Swartz and Stephen Leatherwood, Eds. 1984. The Grey Whale Eschrichtius robustus. Orlando: Academic Press.
  6. Wild Whales - The B.C. Cetacean Sightings Network

Permission is granted by the Vancouver Aquarium Marine Science Centre for classroom teachers to make copies for non-commercial use. This permission does not extend to copying for promotional purposes, creating new collective works, or resale.


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