Grey Whale(Eschrichtius robustus)
- adults range from 11 – 14 metres
- mottled grey skin with scarring and pigmentation
- much of the body is covered with barnacles and whale lice
- no dorsal fin, only a small hump followed by a series of ‘knuckles’ 2/3 of the way back from the head
- low and bushy, up to 3-4 metres in height, often ‘heart’ shaped
- convex trailing edges with a deep notch in the middle
- very inobtrusive at the surface; sometimes referred to as ‘breathing rocks”
- does not breach
- when feeding, makes sharp turns in shallow water and may raise pectoral fins and/or tail flukes out of the water, giving the impression that the whale is struggling or stranded.
Group size / social behaviour
- normally solitary; pairs of mothers and calves are often seen during migration
- only baleen whale in which the upper jaw is longer than the lower jaw.
- the baleen plates are short (5-25 cm) and uniformly cream-yellow in colour.
Can be confused with
- similar size to a humpback whale, but lack of dorsal fin, mottled grey coloring and quiet surface behaviour makes this species very distinctive
Grey whales occur in two distinct populations in the North Pacific. The western grey whale population is restricted to the coasts of China, Korea, Japan and Russia and has been hunted almost to extinction; there are estimated to be fewer than 100 animals in this critically endangered population. The eastern grey whale population was also extensively hunted during the 19th and 20th centuries, but since being protected has rebounded to around 18,000 to 24,000 animals.
The eastern population of grey whales ranges from breeding lagoons in Baja California, Mexico, to summer feeding grounds in the Bering, Chuckchi and Beaufort Seas. Grey whales are the only whales that bear their young in warm, shallow, sheltered bays and lagoons. In the spring, grey whales leave the winter breeding grounds in Mexico and migrate north towards Alaska, usually staying within a few kilometres of shore and passing through B.C. waters. The grey whale migration is one of the longest of any mammal (up to 15,000 – 20,000 km round trip). A small population of a few hundred animals known as “summer resident” grey whales or the “Pacific Coast Feeding Aggregation” remains in the inshore waters of Washington and British Columbia during the summer instead of continuing the migration to Alaska.
Grey whales feed in inshore, shallow areas ranging from the coast of Washington and British Columbia up to the high arctic in the Beaufort Sea. Unlike other baleen whales, grey whales are bottom feeders and use their coarse baleen to strain out small invertebrates (amphibods, ghost shrimp, crab larvae) from the soft muddy bottom in shallow areas, leaving mouth-sized depressions in the sediment. Grey whales also feed on herring eggs and larvae in eelgrass beds during the spring and summer months.
Grey whales are not highly social and only come together the breeding season and during parts of the migration. Calves are born in Mexico during the winter months and are typically up to 5 metres long and weigh about 900 kg at birth. Mothers and calves have a strong bond for the first few months, and mothers often stroke their calf with their flippers and fiercely protect them from attacking killer whales on their migration route. Calves wean at around 8-10 months. Grey whales may reach puberty around 6-12 years, and continue growing up to about 40 years. The lifespan is unknown, but whaling data suggest they may live well over 80 years.
The primary predators of grey whales are transient killer whales, which may attack grey whale calves and yearlings along their migration route. Vancouver Aquarium marine mammal scientist Dr. Lance Barrett-Lennard has been studying killer whale predation on grey whales in False Pass, Alaska, through which the majority of grey whales pass on their way to the Bering Sea. Transient killer whales in False Pass are estimated to kill up to 150 grey whales each year, and have adapted a unique behaviour of caching dead grey whales in shallow waters so that they can consume most of the carcass over the course of several days. Carcasses that wash up on nearby shores also provide an important source of nutrition for brown bears that are just emerging from their hibernation dens.
Status in Canada
The grey whale is designated as Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).
COSEWIC’s assessment of the Eastern North Pacific population of grey whales is as follows:
Grey whales migrate each year from their winter calving grounds in Mexico to their summer feeding areas in northern Alaska, Russia and Canada. Most of the population passes along the BC coastline, and some individuals repeatedly spend the entire summer feeding in BC (about 80). The population increased by 2.5% per year following the cessation of whaling, and peaked, within the range of pre-exploitation estimates, at about 27,000 animals in 1998. The extent of recovery of the summer resident group is unknown. However, over one-third of the population died from 1998 to 2002 (possibly due to a lack of food in Alaska). Birth rates, survival rates and other indicators suggest that the decline has ceased and that the population is stable or increasing since 2002. The whales are susceptible to human activities in their 4 breeding lagoons in Mexico, as well as to entanglement in fishing gear and collisions with boats throughout their range. Underwater noise associated with proposed oil development in BC could alter migration patterns. The small group of summer-resident whales could also be threatened by subsistence whaling in the USA.
Calambokidis, J., J.D. Darling, V.B. Deecke, P. Gearin, M. Gosho, W. Megill, C.M. Tombach, P.D. Goley, C. Toropova and B. Gisborne. 2002. Abundance, range and movements of a feeding aggregation of gray whales from California to southeastern Alaska. Journal of Cetacean Research and Management 4: 267-276.
Darling, J.D., Keogh, K.E. and Steeves, T.E. 1998. Gray whale (Eschrichtius robustus) habitat utilization and prey species off Vancouver Island, BC. Marine Mammal Science 14: 692-720.
Dunham, J.S. and Duffus, D.A. 2002. Diet of gray whales (Eschrichtius robustus) in Clayoquot Sound, British Columbia, Canada. Marine Mammal Science 18: 419-437.
Jones, M.L., Swartz, S.L. and Leatherwood, S. 1984. The Gray Whale. Academic Press, London.
Jones, M.L. and Swartz, S.L. 2002. Gray Whale, Eschrictius robustus. In: Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (eds) Encyclopedia of Marine Mammals. Academic Press, San Diego. pp 524-536.
Rugh, D.J., Hobbs, R.C., Lerczak, J.A. and Breiwick, J.M. 2005. Estimates of abundance of the eastern North Pacific stock of gray whales (Eschrichtius robustus) 1997-2002. Journal of Cetacean Research and Management 7: 1-12.
Weller, D.W., Burdin, A.M., Würsig, B., Taylor, B.L. and Brownell, R.L. Jr. 2002. The western gray whale: a review of past exploitation, current status, and potential threats. Journal of Cetacean Research and Management 4: 7-12.