The moment an orca pod surrounded a lone blue whale has been captured on camera.
The killer whales can be seen harassing the enormous whale, forcing it to swim away.
The clip was uploaded to YouTube by Monterey Bay Whale Watch, who wrote: "While watching Emma's family group they suddenly came across a Blue Whale in their path!
"Although Humpbacks stand up to Killer Whales and trumpet blow at them, Blue Whales are easily startled by Killer Whales, and flee the scene!
"If you watch closely in the second clip you can see the adult Blue Whale porpoising away, swimming at full speed out of the water on the other side of our boat in the upper left hand corner."
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.
Blue whales are the largest animals ever known to have lived on Earth, weighing as much as 200 tonnes and measuring up to 100 ft long.
According to National Geographic, the tongue of a blue whale can weigh as much as an elephant.