The largest animal ever known
Blue whales are the biggest animals known to have lived. They filter huge volumes of seawater for krill and may eat several tonnes a day during feeding season.
Calls built for distance
Blue whales produce extremely low-frequency calls, many at the edge of or below human hearing. Low sounds lose less energy as they travel, so these calls can cross very long distances underwater. Scientists use seabed hydrophones to track blue whale movements by listening for them. Some studies suggest the pitch of certain calls has shifted slightly over decades.
Recovering from whaling
Industrial whaling reduced blue whales to a tiny fraction of their original number. Numbers are rising in some regions, though ship strikes and ocean noise pose continuing risks.
Listen
What it sounds like: Very low-frequency moans and pulses, many below human hearing.
To hear independent recordings, try Freesound. Check each recording’s licence before reusing it. See Media & Sources.
Conservation status follows the IUCN Red List as we understand it at the time of writing. Assessments are revised regularly, so please check the IUCN Red List for the current listing.