Thursday, May 24, 2012

Are Orcas Whales?

Wild orcas (Orcinus orca) off the coast of Alaska
One discussion I have seen and heard numerous times both on the internet and in my discussions with people in person is about the placement of the orca. Is it a whale or isn't it? Since the species is perhaps more commonly referred to as the killer whale, the question of whether the species is truly a whale can be quite confusing. This is especially true of those who do not have a very good understanding of what whales are or what an orca is.

Baleen of a feeding humpback
To begin, orcas are placed into the Order Cetacea, a grouping which includes basically everything that can even remotely be referred to as a whale, This includes those with teeth like the orca, beluga, narwhal, and the dolphins, and those with baleen such as the right, gray, bowhead, and the rorquals. The distinction between the two groups are quite marked, which is why what's in a species' mouth is the deciding factor that splits Cetacea into two distinct Suborders. Suborder Mysticeti includes all of those whales with baleen, and Suborder Odontoceti includes all of the whales with teeth. Yes, I did just say whales with teeth. Odontoceti is also referred to as the "toothed whales" as that is exactly what the term "Odontoceti" means.

A killer whale skull
To many people, the term "whale" only applies to the large, majestic, baleen species that feed on minute organisms such as krill. This is where the argument that "orcas aren't whales, they're dolphins" comes in. Indeed, it is true that orcas are in the same Family (Delphinidae) as most of the species known as "dolphins." Depending on your interpretation of this, you can conclude that orcas are dolphins. However, the simple fact is scientists have placed such species as the dolphins and the orca into a grouping that is still referred to as whales. Thus, the statement "orcas aren't whales, they're dolphins" is rather a moot point as all dolphins are actually whales.

If this isn't enough evidence to make you agree that orcas are whales, consider the fact that phylogenetic studies always place whales, including the toothed ones, as grouping separate in relation to their next closest relatives, such as the hippo. Though the toothed whales and baleen whales did branch away from each other quite some time ago, they share a common ancestor (with teeth, mind you) that can only be called a whale.


Sources are Animal Diversity Web (University of Michigan), University of Bristol, National Oceanic and Atmospheric Administration, and National Geographic. Images are from Wikimedia Commons and are under Creative Commons licenses or copyright free: one, two, three.

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