A large group of killer whales have been spotted off the coast of San Francisco, a long way from their usual feeding grounds along the Washington coast. They were first seen off Half Moon Bay, apparently searching for salmon.

Although killer whales have been seen off the coast before, researchers believe many individuals are now regularly leaving their historic habitat in the Puget Sound area for the abundant waters near the Golden Gate. Senior scientist Ken Balcomb has tracked the pod in Washington for 30 years, said the whales, including a mother and calf, were positively identified through the photos as members of a family group called "K-pod." Balcomb also believes that members of "L-pod" are also in the vicinity which means that as many as 63 whales could be spread out over 30 miles around the Farallones. These particular animals make up two of the three pods of the southern resident killer whale population, so-named because they are the southernmost group of killer whales in the Pacific Northwest.

Killer whales are in fact the largest species of the dolphin family and are found, worldwide. They are one of the fastest marine mammals, reaching speeds of up to 35 mph. Some killer whales feed on seals ,sea lions and other whale species but the southern Washington pods feed almost exclusively on fish, with chinook salmon being their favourite. Their numbers have declined dramatically in the past decade because of pollution and the destruction of the historic salmon habitat. They were declared an endangered species last year by the National Oceanic and Atmospheric Administration. It is unclear whether killer whales once inhabited the Bay Area and the recent sightings will now lead to further research.

Image copyright: James Dorsey