The Mammal Specialists
Biggs' killer whales / Transients/ mammal specialists
'Transients,' or Bigg's killer whales, are the mammal specialists, and while they often have a huge range compared with residents, they also have their favorite hunting spots. We do in fact have some very 'local' transients, which are very particular and loyal to certain locations.
Biggs' killer whales love harbor seals and porpoise, which have a lot of blubber (calories) and don't put up much of a fight. Some will take sea lions, fur seals, or even larger whales, but this is dangerous work and requires some specialized skills... it doesn't happen overnight. Of course, these large brained whales with husky bodies need a lot of fat for calories, so its no wonder that their most common prey are seals and porpoise.
Stealthy and quiet, they sneak up on prey and take them by surprise... if that doesn't do it they might have to take turns and tire them out.
For several years, NGOS dedicated time to finding Biggs' hunting gray whales during their spring migration through False Pass in the Aleutian Islands! Read more about that here.
AT1 or 'Chugach Transients'
The Chugach transients are a genetically unique population of mammal specialists. The are by far the most likely group in our area to spend significant time hunting seals on ice near the glaciers, crossing over shallow moraines in Northwestern, Unakwik, Columbia, and Aialik. Most predation observations have been on harbor seals and Dall's porpoise, and may have been seen once taking a Minke whale.
Sadly, the Chugach transients swam directly through the Exxon Valdez Oil Spill in 1989 and lost 9 members within a year and a half. Before the spill, they numbered 22, and for the last several years, only 7 individuals remain. They have not had a calf since before the oil spill. Because of their unique genetics, we may lose genetic diversity when we finally lose this group. All 7 were sighted in summer 2022, and as of May 2023, AT2,4,9,10, and 18 have been sighted so far.
The Chugach Transients have unique calls that appear to be used when they are separated due to stealthy hunting, in order to regroup afterwards. We are hearing these calls less than we used to. An excellent book about the plight of this group can be found here.
Gulf of Alaska Transients
We have documented close to 150 Gulf of Alaska transients (mammal specialists). Some seem to focus on harbor seals and porpoise for prey, some seem to focus on Steller Sea Lions. In certain regions, groups of transients appear to specialize in predation on whales, but this is rarely observed in Kenai Fjords and Prince William Sound.
The diet of Transient (or Bigg's) killer whales, in rough order of importance, appears to be harbor seals, porpoise, sea lions, fur seals, belugas, and small baleen whales (Minke) or whale calves. Attacks on sea otters and birds occur, but are much more rare and would not provide many calories due to a lack of blubber. It is not clear whether these are training exercises, or are consumed for energy intake.