A mother killer whale and her calf have been caught on camera chasing a sea lion off San Juan Island in Washington state.

Traci Walter operates whale-watching tours in the region – and her tour group was treated to an amazing spectacle as the mother orca taught her calf to hunt.

According to Walter, this group of orca is known as the T123s.

The family includes a 32-year-old mother named T123 "Sidney", her 17-year-old son named T123A "Stanley" and her five-year-old daughter named T123C "Lucky".

The whales were hunting the world's largest sea lion – a Steller sea lion. The enormous animals can weigh up to 1.2 tonnes can measure 9 feet.

"They did not kill and consume the sea lion but perhaps used it as a teaching opportunity for the younger calf who was right in the action for a good part of it," Walter said.

The giant sea lions are found off northern Pacific coasts and hunt fish, squid, octopus and occasionally even smaller seals.

Orcas are social animals and live in pods of up to 30, which they stay in their whole lives. They belong to the dolphin family and are efficient hunters, preying on fish, squid, sharks, seals and turtles.

Killer whales can grow up to 10 metres long and weigh more than six tonnes.

The orcas were spotted hunting in Washington state Western Prince Whale Watching/YouTube/Storyful