Hundreds of thousands of blue whales (Balaenoptera musculus) were killed by whalers during the 20th century. They are the largest animal known to have existed, which made them a prime target for whaling.
Blue whales can weigh more than 160 tonnes and reach more than 30 metres long. Although immense in size, they feed only on small shrimp-like crustaceans known as krill. They require large amounts of krill to support their large size.
In winter they migrate to warmer waters closer to the Equator to breed. One population of blue whales feeds on the krill available in Australian waters in the summer and autumn, and migrates northward, likely to Indonesia, to breed in the winter.
The population feeding in Australian waters has the lowest recorded genetic diversity of blue whales in the world (Fig. 1). This population is a member of a subspecies of blue whale, the pygmy blue whale (B. m....
