Biodiversity protection

West Coast Bigg’s (Transient) Killer Whales

photo: Rachael Merrett

Bigg’s killer whales, also known as Transients, are famous around the world because of their fantastic and dramatic hunting soirees. They are the mammal hunters. Many videos and documentaries about Bigg’s killer whales have revealed why these orcas are top predators in the sea. Able to take down Steller sea lions weighing in at over 1100kg, with canines similar to that of a Grizzly bear, Bigg’s killer whales are a feared predator among other marine mammals.

Along the coast of the Pacific Northwest, West Coast Bigg’s killer whales number around 400 individuals. They have a vast home range which extends from Alaska to Northern California, and with a tendency to be continuously on the move, it’s difficult to track every single whale in the population year-to-year. Transient killer whales were listed as Threatened under the Species at Risk Act (SARA) in 2003. In recent years, their population has been growing, with more and more sightings within the Salish Sea year round. A significant factor in the population rebounding is the return of Harbour Seal populations to stable, healthy levels for the first time since the Marine Mammal Protection Act was implemented in 1972.

Learn more about the population of Harbour Seals in British Columbia

photo: Rachael Merrett

Bigg’s killer whales do not interbreed with resident orcas. In fact, genetic studies show that this killer whale eco-type has been genetically distinct from all other eco-types of killer whales for a minimum of 750,000 years. The social structure of Bigg’s killer whales differs from the tight-knit pod structure found in resident populations. Bigg’s killer whales tend to travel as a matriline—a female and her offspring, however, members may split off from the group, especially mature daughters and any of their offspring. Because Transients hunt mammals, the optimal number of whales in one group appears to be about 3-7 individuals. This structure allows them to effectively hunt while keeping detection by their prey to a minimum.

Bigg’s killer whales eat a variety of marine mammals including Harbour seals, Harbour porpoises, Steller and California sea lions, Dall’s porpoises, Pacific White-Sided dolphins, and occasionally other whales such as Minkes, and juvenile Grey and Humpback whales. Because they are at the top of the food chain, they accumulate high levels of toxins in their bodies which can impair their immune systems, reproductive systems and the development of fetuses.

A Bigg’s History

Dr. Michael Bigg is recognized as the founder of modern whale research. He was a Canadian Fisheries and Oceans scientist who in the 1970’s was tasked with conducting the first survey of killer whales on the west coast.  This survey was to evaluate how big the population really was so that DFO could set quotas for the live capture industry that was going on at the time.

Through countless hours of observation on the water and tireless hours spent looking at photo proofs under a magnifying glass, Dr. Bigg was the first to discover that killer whales can be individually identified because they each have unique saddle patches, dorsal fin shapes, and nicks, scratches and scars. Being able to identify individuals allowed scientists to understand the social relationships and travel patterns of these killer whales.

While studying what is now known as the Southern Resident killer whale population, Dr. Bigg and his colleagues recognized that different groups of killer whales came in and out of the area and did not associate with the Resident killer whales. He called these mystery orcas the Transients.

Sadly, Dr. Bigg passed away in 1990. His memory was honoured when the next baby orca was born into the Southern Resident killer whale population. Mike or J-26 was born in 1991 and his name carries on the memory of Dr. Michael Bigg. Because of his incredible contributions not only to the understanding of killer whales, but also to cetacean research worldwide, Transient killer whales have been renamed Bigg’s killer whales in his honour.

Learn More About Bigg’s Killer Whales!

Infanticide in a mammal-eating killer whale population

Cultural traditions and the evolution of reproductive isolation: ecological speciation in killer whales?

Clash of titans: Killer whales do battle with humpbacks off B.C. coast

High PCB Concentrations in Free-Ranging Pacific Killer Whales, Orcinus orca: Effects of Age, Sex, and Dietary Preference

The Marine Detective: What’s the Bigg’s Deal?!

DFO’s Photo Identification Catalogue of Bigg’s (Transient) Killer Whales From Coastal Waters of British Columbia, Northern Washington, and Southeast Alaska