Friday, January 28, 2022

Killer whales stay longer than before in the Ice-free Arctic Ocean

The reduction in sea ice may be opening new hunting opportunities for killer whales

Killer whales or orcas may not be giant whales but are intelligent and adaptive predators. They can come up together and 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. It is a potential reason for the ecological imbalance.

Recently, a researcher from the Cooperative Institute for Climate, Ocean, and Ecosystem Studies, Brynn Kimber, presented the study, “Tracking killer whale movements in the Alaskan Arctic relative to a loss of sea ice,” Dec. 2 Seattle at a meeting of the Acoustical Society of America.

Underwater Microphones placed off Alaska’s western and northern coasts show that killer whales have spent more time than previously recorded in the Arctic. It followed a decrease in summer sea ice.

Killer whales travel to different areas in search of prey. There is a risk of ice entrapment in the Arctic ocean. Despite this, analysis of acoustic data recorded by four underwater microphones from 2012 to 2019, Seattle-based team found killer whales spend more time in the arctic ocean. Their readings indicate that this more extended stay directly follows 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,” said Kimber. “This is likely in response to a longer open-water season.”

“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.”

Certain prey species use ice to hide from predators, and they may not use this trick due to the reduction in ice in the Arctic Ocean. Ultimately it is opening new hunting opportunities for killer whales.

Last fall, another study led by a different CICOES researcher showed the first direct evidence of killer whales attacking bowhead whales in the Arctic.

This vulnerability, Kimber said, is likely to increase due to longer open-water seasons.

“Although there is high spatial and interannual variability, the September Arctic sea-ice minimum is declining at an average rate of 13% per decade when compared to values from 1981 to 2010,” Kimber said. “Killer whales are being observed in the Chukchi Sea (in the Arctic Ocean) in months that were historically ice-covered, and more consistently throughout the summer.”

Journal Reference

  1. Tracking killer whale movements in the Alaskan Arctic relative to a loss of sea ice. The Journal of the Acoustical Society of America 150, A284 (2021); DOI: 10.1121/10.0008306

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