Habit: Generalist

Blue whales are long lived, with a lifespan estimated at 30 to 90 years. The age of sexual maturity is uncertain, but estimated to be five to fifteen years for both sexes. Reproductive activity takes place during winter, in the warmer waters of their range, and females breed every two to three years. The specific breeding grounds are not known with any accuracy. Gestation lasts ten to twelve months. Newborns measure seven meters and are nursed six to seven months.

Blue whales are usually seen alone or in pairs. However, scattered aggregations of a dozen or more may develop on prime feeding grounds. Although shorter dives are most common, dives of up to 30 min, generally interspersed with long series of shorter surfacings (at 15-20 sec intervals), have been recorded. Fluking-up is not uncommon, although not all blue whales are "flukers." Remarkably, some blue whales have been observed breaching.

Focused diet: Crustaceans

Blue whales feed almost exclusively on crustaceans, particularly euphausiids (krill). Blue whales may ingest two to four tons of food per day.

Feeding mode: Lunging

Blue whales are known to feed on the surface and at depth, and in some places have been recorded exploiting deep scattering layers in which plankton are concentrated.

Prey species include:

Southern Ocean population: Euphausia superba

North Pacific population: Thysanoessa inermis, T. longipes, T. spinifera, Nematoscelis megalops, Euphausia pacifica, Thysonoessa raschii, Pleuroncodes planipes, Nyctiphanes simplex

North Atlantic population: Thysonoessa inermis, Temora longicornis, and Meganyctiphanes norvegica, Thysonoessa raschii

Main threats include:

Ship strikes

Fisheries bycatch

Entanglement in debris/fishing gear

Noise pollution

Conservation status:

The global population of blue whales prior to whaling may have been as high as 300,000. It was not until powerful boats and deck-mounted harpoon cannons were developed that blue whales could be hunted by whalers. From the turn of the twentieth century until the mid-1960’s blue whales were intensively hunted throughout the world’s oceans. During the 1930-1931 hunting season, over 30,000 blue whales were killed worldwide, the highest annual hunt on record.

By 1966 blue whales were protected in all waters by the International Convention for the Regulation of Whaling. Despite protection, the population remains substantially below pre-whaling levels. The IUCN lists three geographically distinct populations: Southern Ocean (endangered, population estimated at 400-1400), North Atlantic (vulnerable, population estimated at up to 4000), and North Pacific (lower risk, population estimated at up to 4000) but considers the pygmy blue whale as “data deficient”, in that too little is known about the population to judge its conservation status. In the U.S. blue whales are listed as an endangered species and are also protected by the Marine Mammal Protection Act. Some illegal hunting has been documented since 1966, but presently this is not a major threat. Other conservation concerns include entanglement in fishing gear, collisions with ships, and possible threats from low-frequency acoustic research currently underway.

For current information on the conservation status of this species, please consult the following websites.

• IUCN Species Redlist

• CITES web-page

• U.S. FWS Threatened and Endangered Species System (TESS)

• International Whaling Commission

• U.S. NMFS Stock Assessment Reports

• Convention on Migratory Species (Appendix I)

To sounds catalog, to museum specimen catalogs, to other important pages.

Genetics: Genbank

Sounds: National Marine Mammal Laboratory

Museum Collections: Smithsonian Institution

Images: National Marine Mammal Laboratory, Ocean Alliance

Gaskin, D.E. 1982. The Ecology of Whales and Dolphins. Heinemann, Portsmouth, NH.

Leatherwood, S. and R.R. Reeves. 1983. The Sierra Club Handbook of Whales and Dolphins. Sierra Club Books, San Francisco, CA.

National Marine Fisheries Service. 1998. Recovery plan for the blue whale (Balaenoptera musculus). Prepared by Reeves, R.R., P.J. Clapham, R.L. Brownell, Jr., and G.K. Silber for the National Marine Fisheries Service, Silver Spring, MD. 42 pp.

Schoenherr, J.R. 1991. Blue whales feeding on high concentrations of euphausiids around Monterey Submarine Canyon. Canadian Journal of Zoology. 69: 583-594.

Barlow, J. 1994. Recent information on the status of large whales in California waters. NOAA Technical Memorandum NMFS SWFSC 203:27 pp.

Mizroch, S.A., D.W. Rice, and J.M. Breiwick. 1984. The blue whale, Balaenoptera musculus. Marine Fisheries Review 46:15-19.

Sears, R. 2002. Blue whale Balaenoptera musculus. Pp. 112-116 in W.F. Perrin, B. Wursig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.

Yochem, P., and S. Leatherwood. 1985. Blue whale Balaenoptera musculus (Linneaus, 1758). 193-240 in S. H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Vol. 3: The sirenians and baleen whales. Academic Press.