Blue whales are the largest animals ever known to have lived on Earth.

Scientific name: Balaenoptera musculus

Physical description and related species

The biggest blue whale ever weighed was nearly 200 tonnes and over 30m in length.

Distribution and abundance

Distribution: Blue whales, along with minke whales, venture further into the sea ice than other rorquals (such as the humpback and sei whales), and have been seen near 78°S in the Ross Sea. Non-lethal science using mark-recapture methods and acoustic tracking is being undertaken to determine the distribution and abundance of blue whales following the ban on commercial exploitation imposed by the International Whaling Commission in 1964.

Pygmy blue whales are never found south of 50°S, and feed off the southern Australian coast in summer. They grow to ‘only’ about 25m.

Threats: Southern Hemisphere ‘true’ blue whales were reduced from around 225,000 individuals pre-exploitation to probably less than 2,000 now. In just one area — South Georgia — 30,000 blue whales were killed in the 1930–31 season alone.

Conservation status: endangered

Breeding

The breeding grounds of Southern Hemisphere blue whales are still unknown but are thought to lie somewhere in the deep oceanic waters of the tropical South Pacific, Atlantic and Indian Oceans.

A new born blue whale calf weighs 2.5 tonnes and can, in the latter stages of suckling, put on 100kg a day.

Diet and feeding

A blue whale gulps up to 50 tonnes of water and krill in one feeding mouthful, but swallows only the krill.

'True’ blue whales are one of the fussiest eaters in the Antarctic, usually eating only Antarctic krill (Euphausia superba).

Whale song

Blue whales off Sri Lanka have a song which consists of only four long, low notes.

Low frequency moans of blue whales, some of them lower than human hearing, can theoretically travel several thousand kilometres, and at close range are as loud as a jumbo jet taking off.

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