Earth's largest animal nearly vanished before a 1966 ban
Blue whales stretch to about thirty meters and two hundred tonnes, outranking every known animal. Polar summer feeding and tropical winter breeding once filled the oceans—until industrial whaling emptied them. The International Whaling Commission barred the hunt in 1966; recovery remains fragile.
Balaenoptera musculus is a baleen rorqual and the largest living marine mammal. Confirmed maxima reach roughly 29.9–30.5 meters and 190–200 tonnes, making it the biggest animal known ever to have lived. Most populations shuttle between high-latitude summer feeding grounds and lower-latitude winter breeding areas, though some stay year-round or migrate only partly by age or sex. They filter-feed, taking almost nothing but krill in enormous mouthfuls. The species ranges across the globe yet is largely absent from the Arctic Ocean and from the Mediterranean, Okhotsk, and Bering seas; at least four subspecies are traditionally recognized.
Once common in nearly every ocean, they were driven near extinction by commercial whaling until the 1966 IWC ban. The IUCN still lists blue whales as endangered. Linnaeus may have punned when he chose musculus—muscle or little mouse—for Systema Naturae; Balaenoptera means winged whale. Early naturalist Robert Sibbald described them, hence "Sibbald's rorqual," while whalers' "sulphur bottom" nickname came from yellow diatom films on some bellies. North Atlantic blues summer from New England to Greenland, especially in the Gulf of St. Lawrence, while the eastern North Pacific stock feeds off California and then heads south to the Gulf of California and toward Costa Rica for winter and spring.
A 2018 study places Balaenopteridae's split from related families between about 10.5 and 5 million years ago in the late Miocene. Whole-genome work places sei whales as their nearest kin and treats gray whales as the next branch out, and finds past gene flow involving minke ancestors plus high diversity within blues. Rare hybrids with fin whales appear in historical catch records. Live blue-fin hybrids have since been spotted in the Gulf of St. Lawrence and the Azores, and a 2024 genome analysis of North Atlantic blues found about 3.5 percent of their DNA came from fin whales, with genes moving in one direction only.
Source: Blue whale
