Orcas practise drowning their friends as a way to learn how to hunt large prey like blue whales.

Footage captured by film crews off the coast of Australia shows a pod of killer whales honing their hunting skills in a world first.

Young orcas surround their mock prey, which is a fellow pod member playing the role of a hunted beast, before forcing it underwater and covering its blowhole.

The blowhole on their back is what allows the orca to breathe and if they can not reach the surface often enough, they will run out of oxygen and drown.

Video of the behaviour was captured for the first time by BBC staff recording the new Parenthood documentary narrated by Sir David Attenborough.

The clips, shared with The Times, show a matriarch leading the macabre lesson with young orcas off the coast of Bremer Bay in Western Australia.