Killer whales are some of the most widespread mammals in the world. A recent study led by the University of British Columbia in Canada has found a previously unknown type of killer whale living off the west coast of the United States. These so-called “outer coast transient whales” prefer deep water for hunting, have a unique high-pitched vocal dialect, and prey on large sea mammals, including even other species of whales, such as the baby grey whales.
By analyzing over 100,000 photographs of killer whales taken off the United States west coast, the research team discovered a species that lives and hunts hundreds of kilometers further from the coast than the typical killer whales, in the offshore waters between Oregon and central California.
“Killer whales are found all over the world,” said study lead author Josh McInnes, a master’s student at the University of British Columbia. “They spend most of their time in coastal waters, but we’re now finding that they do inhabit the offshore oceanic waters. And there’s basically nothing known about them out there.”
The outer coast killer whale is thought to be a subspecies of Bigg’s killer whales, which are known for their highly coordinated hunting patterns. However, researchers found significant differences between these whales and their coastal cousins. While Bigg’s transients hunt smaller mammals, such as harbor seals and porpoises, the outer coast ones prefer elephant seals, oceanic dolphins, and even grey whale calves.
Besides having different habitats and dietary preferences, outer coast and nearshore whales also seem to have different dialects. According to McInnes, because of the need to be heard above the roar of offshore winds, the outer coast whales use higher pitched calls than their nearshore counterparts.
“People talk about biodiversity a lot,” said Lawrence Dill, a behavioral ecologist at Simon Fraser University in British Columbia. “Most people tend to understand that as species diversity. It’s important to realize that within species, sometimes even within a population, there’s behavioral diversity.” The discovery of outer coast transient whales is an important step forward in understanding the diversity characterizing the world’s killer whales.
The study is published by the National Oceanic and Atmospheric Administration.