Blue whale

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The blue whale (Balaenoptera musculus) is the largest animal ever known. It can reach about 30 meters (98 feet) long and weigh around 190–200 tons. Its body is a greyish-blue on top and lighter underneath. Some whales have yellowish bellies from tiny diatoms, which gave the old nickname “sulphur bottom.”

Where it lives and subspecies
Blue whales are found in oceans around the world, but they’re not common in the Arctic, Mediterranean, or parts of the colder seas. There are several recognized subspecies, including the northern and southern forms, the pygmy blue whale, and others in different oceans. Some populations may form separate groups or populations that don’t mix much.

What they eat and how they feed
Blue whales are filter feeders that eat mostly krill. They swim with their mouths wide open to lunge through big swarms of krill, pushing water out with their baleen plates and swallowing the prey. A single mouthful can contain huge amounts of krill, and a whale can ingest many tons of prey in a day.

Behavior and life history
Blue whales are usually solitary or found in small groups, though large gatherings can happen when food is plenty. They are deep-divers and travel long distances between feeding and breeding areas. Calves are born very large, about 6–7 meters (20–23 feet) long, and gain weight rapidly on their mothers’ milk. Mothers and calves stay together for months, and whales can live for several decades, with some older individuals reaching 80–110 years.

Communication and predators
Blue whales produce some of the loudest sounds in the animal kingdom. Their calls are low-frequency and vary by region and season. Orcas are their main natural predators, but attacks on adults are rare.

Conservation status and threats
Blue whales were hunted almost to extinction in the 20th century. The International Whaling Commission banned hunting in 1966, and many populations have slowly recovered, but they are still classified as Endangered. Major current threats include ship strikes, ocean noise, pollution, and changes in climate and prey availability. Protecting shipping routes, reducing noise, and safeguarding feeding grounds are important for their continued recovery.

Quick facts
- Longest confirmed blue whale: just under 30 meters (about 98 feet).
- Weight at large sizes: around 180–200 tons.
- Calves need huge amounts of milk—young whales grow very fast.
- A single day’s krill diet can amount to about a ton or more.