In most toothed whales, the internal organs in the skull are squashed into the left side to make way for soft tissues which help them to echolocate.

Echolocation is a technique used by animals that need to navigate and hunt in the dark. They emit high-pitched sounds which bounce off objects and are reflected back at the animal. These reflected noises help the brain to build an image of the animal’s surroundings, allowing them to ‘see’ where objects are and how they are moving.

Only some whales, dolphins, and porpoises (collectively known as cetaceans) can do this. Cetaceans are split into two groups, those with teeth and those with baleen. Baleen whales (mysticetes), including blue whales and humpback whales, filter ocean water for tiny crustaceans and fish and do not need to ecolocate. Cetaceans with teeth (odontocetes) include dolphins, killer whales, belugas, narwhals, and sperm whales, and these animals hunt in a variety of marine environments. Echolocation helps them do it.