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Killer whales, known interchangeably as orcas, are found in every ocean in the world in both coastal and open ocean waters. They are the most widely distributed of all cetaceans, and it is estimated that worldwide there about 50,000 killer whales. There are many different populations around the world, which are delineated into so-called ecotypes (i.e. forms), and some of these may even be different species or subspecies.

The distinct black and white coloration of killer whales is famous: their white eye patches and saddle-patch contrasting with the black upper-body coloring make them an easily identifiable cetacean. Many of us had our first introduction to killer whales through picture books, movies, or even at zoos or aquariums.

So you may be wondering: where does the name “killer whale” actually come from? Well, this is actually a misnomer! The original term, coined by whalers who would regularly see these animals while out on their whaling boats, was in fact “whale killers” as they observed mammal-eating orcas hunting and killing larger whale species. Some people prefer the name orca for this reason (which originates from their latin name, Orcinus orca), however for this blog post we are going to use the term killer whale.

One of the least well-known killer whale ecotypes, these Type D killer whales are found in Antarctica. Photo credit: National Geographic.

Killer whales are in fact the largest species of dolphin, and have complex social structures with whales tending to stick with their original pods. Pods, which is the name for groups of dolphins, consist of 2 to 15 animals, however larger groups are sometimes observed during social interactions, mating, or seasonal availability of food.

Speaking of food, what do killer whales eat? Great question: it depends! Depending on the ecotype, killer whales eat fish (e.g. salmon, herring), sharks, or even marine mammals including large whales, porpoises, seals and sometimes sea lions. Many of the ecotypes have become highly specialized to predate on a specific species or type or prey, for example killer whales in New Zealand have specialized in catching and eating stingrays and shark, whereas the Southern resident killer whales here in the Pacific specialize on salmonids.

Below, we’ll discuss more about one of the killer whale ecotypes we have here in the Salish Sea, the transient or Bigg’s killer whales. Stay tuned to our next blog post, where we’ll tell you all about the famous Southern resident killer whales, and why you should be concerned about them!

Transient Killer Whales

There is only one defined species of killer whale throughout the world, yet this species can be divided into multiple ecotypes based on appearance or diet. Here in Washington State, we most commonly see the famous fish eating Southern “Resident” killer whales (SRKW), as well as the marine mammal eating Bigg’s or “Transient” killer whales. The terms “resident” and “transient” do not necessarily define the different ecotypes’ range, rather it distinguishes them based on their diets. There are currently around just over 300 Bigg’s killer whales throughout Washington, comprising multiple pods of two to six individuals each that will occasionally group up for hunting or socializing events.

Named after orca researcher Michael Bigg, the transient killer whales most commonly prey on harbor porpoises and various pinnipeds throughout the Salish Sea, such as harbor seals or California sea lions. Though rare in the Salish Sea, these whales will also prey on smaller minke whales or young grey whales – an energy demanding investment for a potentially high food reward. These whales are silent hunters when compared to the noisy SRKW, using the element of surprise on weary mammals that could distinguish their calls as danger. Though only slightly larger than the residents, Bigg’s killer whales most distinguishing feature when identifying them here in Washington is a closed saddle patch – a solid white patch behind the dorsal fin compared to a black finger in that of the residents.

Note the so-called “closed” saddlepatch on this transient killer whale. Photo credit: Gary Sutton.
The Southern resident saddlepatch is “open”. Photo credit: Michelline Halliday.

cindy.elliser@pacmam.org

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