Formerly known as ‘transients’, Bigg’s orca are often referred to as the wolves of the seas. They are the whale that lead to the term “killer whale” since they hunt marine mammals, including other whales. What sets Bigg’s orca apart from the fish-eating resident orca is that Bigg’s prey on marine mammals. Most commonly, they predate on harbour seals, but they are known to also hunt harbour porpoise, Dall’s porpoise, Pacific white sided dolphins, gray whales, minke whales and Steller sea lions. Seabirds are also attacked, but not usually eaten. Many times juvenile orca are seen “playing” with seabirds, which might be an important means of developing hunting techniques.
They are more difficult to study because they live in smaller groups, usually consisting of 2-6 individuals. The family structure of Bigg’s orca is much more fluid, with families breaking apart and joining other families for periods of time. However, like residents the relationship between a mother and her oldest son lasts a lifetime.
The range of Bigg’s orca on the west coast of North America stretches from southern California to the Aleutian Islands of Alaska. Bigg’s orca cover a large area in search of prey, continuously on the move to maintain their stealth tactic of hunting. If they stayed in the same area for a prolonged amount of time, prey would be alerted to their presence, thus reducing successful hunting. With this on-the-move lifestyle, they can easily travel over 100km a day.
All Bigg’s orca share a common set of vocal signals, with some small varieties existing, but because of the Bigg’s fluid social order, they have not developed the unique calls/dialects, like resident orcas. Additionally, because this population travels mostly in silence to prevent other species from detecting them, the opportunity for a specific dialect to be passed on to family members is minimized. When we detect Bigg’s orca call types over the hydrophone we know which population we are recording but cannot determine the family group by distinct acoustic call types. They tend to use passive sonar, listening for the sounds of their prey, such as a splash from a swimming seal or a whistle from a dolphin. This is part of their stealth hunting style/tactic. If they were vocal while hunting, it could alert their prey to their presence. However, after a successful hunt, Bigg’s can be quite vocal when socializing.