A new study published in the journal “Royal Society Open Science” argues that two orca groups — known as resident killer whales and Bigg’s killer whales — should be considered separate species due to new DNA evidence.

Both whales are found in the North Pacific Ocean, among the western North American coast and eastern Asian coast.

A singular species, but different forms

Currently, all killer whales are classified as one species known as Orcinus orca, according to Smithsonian Magazine. Scientists differentiate the different types of killer whales by using what is known as ecotypes.

Ecotypes are another way to describe the different forms killer whales come in, per SeaWorld. According to the Whale and Dolphin Conservation, there are 10 known ecotypes, or types, of orcas within the species:

  • Resident orcas.
  • Bigg’s orcas.
  • North Atlantic Type 1 orcas.
  • North Atlantic Type 2 orcas.
  • Offshore orcas.
  • Type A orcas.
  • Type B (large) orcas.
  • Type B (small) orcas.
  • Type C orcas.
  • Type D orcas.

The Atlantic reports that the new study argues that Bigg’s orcas and resident orcas are distinct species, not ecotypes as previously thought. If accepted by the Society for Marine Mammalogy, the classification of killer whales could change as soon as later this year.

What are the new orca species?

The study explains that there are two ecotypes of killer whales that should be considered their own individual species due to their genetic coding and pod cultures — the Bigg’s orca and the resident orca, both found in the eastern North Pacific Ocean.

SeaWorld explains that orcas in the eastern North Pacific fall into three categories: transient (Bigg’s), resident and offshore.

Here are some of the differences scientists found in the study between the Bigg’s orca and the resident orca, according to Smithsonian Magazine and Scientific American :

  • Resident orcas form large pods, but Bigg’s orcas have smaller pods that are maternally related.
  • Resident orcas hunt using echolocation, but Bigg’s orcas hunt silently.
  • Resident orcas live near shore and eat salmon, but Bigg’s orcas live farther out in the ocean and eat mammals.
  • Resident orcas have a round dorsal fin while Bigg’s orcas have a straight, pointed dorsal fin.
  • The skulls and teeth shape differ between both types.

According to The Atlantic, this new study takes into account how factors such as communication, behavior and culture can create a species just as much as genetics and physiology currently do.

The study proposes that orcas should be classified into three distinct species: transient (Bigg’s), resident and the original Orcinus orca, per The Atlantic.

Researchers also noticed how Bigg’s orcas and resident orcas would not breed with each other even though they lived in close proximity, Scientific American reports. When they conducted genetic testing between the two ecotypes, they found out that both groups of orcas had diverged from one another around 300,000 years ago.

The study proposes that the Bigg’s killer whale and resident killer whale be renamed as the species Orcinus rectipinnus and Orcinus ater, respectively, instead of the singular name Orcinus orca.

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