Underwater microphones placed off the western and northern coasts of Alaska show that killer whales have spent more time than previously recorded in the Arctic, following the decrease in summer sea ice.

Killer whales are intelligent, adaptive predators, often teaming up to take down larger whales as prey. Continuous reduction in sea ice in the Arctic Ocean is opening areas to increased killer whale dwelling and predation, potentially creating an ecological imbalance.

Killer whales will often travel to different areas to target varieties of prey. In the analysis of acoustic data four underwater microphones recorded from 2012 to 2019, researchers found that killer whales are spending longer in the Arctic Ocean in more recent years, despite risks of ice entrapment there. Their readings indicate this change is directly following the decrease in sea ice in the area.

“It’s not necessarily that killer whales haven’t been reported in these areas before, but that they appear to be remaining in the area for longer periods of time,” says Brynn Kimber, a researcher from the Cooperative Institute for Climate, Ocean and Ecosystem Studies (CICOES). “This is likely in response to a longer open-water season.”

The study didn’t set out to focus on the killer whales, or orcas, says Kimber, who was surprised by the results.

“Our work mostly centers on examining the migration patterns of species through the Bering, Chukchi, and Beaufort seas, based on acoustic presence or absence. But when looking for other species, like beluga whales, I noticed more and more killer whales in areas where I didn’t expect them. That was what motivated me to take a closer look at our killer whale detections.”