Killer Whales Are Currently Regarded As A Single Species, But There May Be Enough Differences Between Two Orca Populations In The Eastern North Pacific To Start Classifying Them As A Separate Species
In the eastern North Pacific, there are two populations of orcas with qualities that make them stand out from others.
These differences may be enough to justify classifying them as separate species, according to a study published in Royal Society Open Science.
Currently, all killer whales are regarded as a single species. They live in oceans around the world. Different groups are found in diverse climates, have varying diets, and make a range of sounds.
The new study looks at the traits of two populations of orcas—resident and Bigg’s killer whales. Bigg’s are also known as transient killer whales.
“These two types are genetically two of the most distantly related types in the whole world,” Phillip Morin, a geneticist with the Southwest Fisheries Science Center at the National Oceanic and Atmospheric Administration (NOAA) and co-author of the study, said.
“They’re not just behaving differently. They really are on these evolutionary trajectories which we consider to be different species.”
Resident and transient killer whales inhabit the waters of the eastern North Pacific. Residents feed on fish and live near the shore, while transients eat marine mammals and swim farther out in the ocean.
Additionally, residents tend to gather in large, stable communities. On the other hand, transients form smaller groups of orcas that are maternally related and hunt silently with each other.
Residents hunt in larger groups using echolocation, producing sonar clicks more often than transients.
David Hutchison/Wirestock – stock.adobe.com – illustrative purposes only, not the actual orca
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The size and shape of their bodies, dorsal fins, and jaws also differ. Residents have more rounded dorsal fins. In contrast, transients have more pointed and straight dorsal fins.
The two groups live in areas that overlap, but they don’t interact with each other much. Researchers have noticed that they avoid one another and sometimes behave aggressively toward each other. They also have never interbred, even though they live close enough to do so.
A genetic analysis suggests that they are two distinct groups and have been on separate paths of evolution for a long time.
Evidence shows that residents branched off from their ancestors around 100,000 years ago, while transients diverged between 200,000 and 300,000 years ago.
Based on the research, there is enough variance in their DNA to categorize them as two different species.
The Society of Marine Mammalogy will decide whether to officially deem resident and transient killer whales as two new species at their next annual review.
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