Length: 24 – 30m (79 – 98’)
Weight: 75 – 130 tons
Population size in Canada: Atlantic – <300      Pacific – <300
Population size in World: 5,000-12,000, however, estimate is not recent
Conservation status in Canada: Endangered (COSEWIC/SARA)
Conservation status in World: Endangered (IUCN)


Latin Name: Balaenoptera musculus
Other Names: Great northern rorqual, Sibbald’s rorqual, Sulphur-bottom
Suborder: Mysticete (Baleen Whale)
Family: Balaenopteridae

Field Identification
    • up to 98 feet in length
    • very large streamlined body
    • mottled blue/grey colour pattern on body
    • very broad, flat U-shaped head
    • two blowholes
    • huge blowholes & splashguard
    • jet black or blue-black baleen, ~90cm – 1 m in length
    • throat grooves extend beyond navel area
    • very tall, columnar blow/spout (~30-40’ in height)
    • small triangular dorsal fin set very far back on body
    • very large tail, ~ 21-25’ (6.5 – 7.5 m)
    • thick tail stock
    • fluke briefly lifted out of the water on some dives
    • group size: 1-2 ( less commonly 1-5)

Blue whales are the largest animal to have ever lived on earth, larger than any other whale or even dinosaurs. Individuals up to 30 m (98’) have been recorded with females being slightly larger than males. They have a huge body which is a mottled, blue-gray colour. The mottling pattern is highly variable and can be used to identify individuals. The belly of a blue whale can be white, blue or even sometimes yellow, which is why they can be known as the “Sulphur-bottom”. This yellow colour is caused by diatoms (algae) on their skin. Their heads are very broad, flat and long, up to a quarter of the total length of their bodies. They also have a ridge running along the top of their heads and a very large splashguard in front of their two blowholes. Blue whales have 55 to 68throat grooves which expand when the whale is feeding and extend at least as far as the navel. Their baleen is black can be up to 1 metre long. When they breathe out, their blow is very tall and columnar and can range from 6 to 12 metres high. Their tiny dorsal fin is set very far back on the body and appears well after the blowholes when the whale surfaces.

Life History

Blue whales are thought to live for at least 80-90 years and probably longer. They reach sexual maturity between 5-15 years of age, although 8-10 years is more likely. Female blue whales give birth every 2-3 years in winter after a 10-12 month gestation period. The calves, which weigh 2-3 tons and measure 6-7m long at birth, are weaned at 6-8 months when they are approximately 16 m long.


Blue whales are found in all oceans and inhabit coastal, shelf and oceanic waters. There are 3 main populations of blue whales: one in the North Pacific, another in the southern hemisphere, especially in the cold waters above Antarctica and a third in the North Atlantic. Movements of blue whales are complex. Much of the population annually migrates between low latitude tropical waters in the winter and higher latitude polar waters. Blue whales are common in the waters of the northern Gulf of St. Lawrence, are often sighted in the offshore waters on the Scotian Shelf and rarely in the Bay of Fundy and in other coastal areas of the Maritime Provinces.


Blue whale feed just below the surface on krill and/or other crustaceans.


Blue whales generally swim quite slowly at speeds of 3-6km but can travel at over 30km/h if they are chased. Very little is known about the social structure of blue whales. Like other baleen whales, they tend to travel alone or in small groups. Blue whales usually dive to about 150 metres but can go deeper. Younger blue whales have been seen breaching but adults breach very rarely, if ever. Adults usually feed by themselves or in pairs, often widely spaced out. This could be because they each need a large area of ocean to find enough food. Blue whales emit the loudest sounds of any animal. They emit low frequency sounds that can travel hundreds of kilometres in deep water allowing individuals to communicate over great distances. The dorsal fin appears well after the blowholes when the whale surfaces and the large, triangular flukes are often raised during a dive.

Population size

It is not clear how many blue whales there are. All populations were drastically reduced by whaling, some by perhaps 99% of their original numbers. It is very unclear as to whether their population has made any significant recovery from this. Global population estimates are thought to range from 5,000 – 12,000; however, a recent global estimate is not available. The blue whale population for the North Atlantic is estimated to be between 600-1500 individuals while the North Pacific population is estimated to contain between 2000-3000 animals. The Southern hemisphere population, once considered to be the most abundant population (over 300,000 individuals), likely only has 710-1255 animals.


Besides killer whales, blue whales have few natural predators. The only other reported cause of natural mortality has been from entrapment in ice.

While no longer allowed to be whaled, blue whale meat still appears in Japan labeled as other species of whale. Human threats include entanglement in fishing gear, vessel strikes, noise and chemical pollution and disturbance from increasing whale watch activity. The persistence and increase in these threats could limit the recovery of this species. They are also vulnerable to long-term changes in climate, which may already be affecting availability of prey off California.