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Endangered Killer Whales Alter Hunting Behavior Amid Shipping Disturbance

Research reveals changes in hunting patterns and prey preference in the Salish Sea.

Endangered killer whales are changing their hunting behavior and one of the reasons could be disturbance from shipping, reveals new research.

Seasonal use of the inland Salish Sea has also changed dramatically due to shifts in their preferred salmon prey.

The area spans from Olympia, Wash., in the south to the Campbell River, British Columbia in the north, and west to Neah Bay – and includes the cities of Seattle and Vancouver.

She added: “The fish-eating Southern Resident killer whales (Orcinus orca) of the northeastern Pacific are listed as endangered in both the USA and Canada.

“The inland waters of Washington State and British Columbia, a region known as the Salish Sea, are designated as Southern Resident critical habitat by both countries.”

The whales have historically had regular monthly presence in the Salish Sea, with peak abundance occurring from May through September.

The study shares 2018–2022 daily occurrence data to build upon and compare to previously published whale presence numbers and to demonstrate more recent habitat shifts.

Dr. Wieland Shields said: “These changes correspond to identified shifts in prey availability, with the continued decline of spring and summer Fraser River Chinook, the increasing importance of Columbia River Chinook in the diet and the overall increased abundance of fall and winter chum in Puget Sound.”

Based on reports from an extensive network of community scientists as well as online streaming hydrophones, every Southern Resident occurrence was confirmed
either visually or acoustically.

Dr. Wieland Shields said: “Documented here are the first-ever total absence of the Southern Residents in the Salish Sea in the months of May, June, and August, as well
as their continued overall declining presence in the spring and summer, while fall and winter presence remains relatively high.

Whales are intelligent apex predators that capture our imagination. They can cooperate – following prey more than a mile beneath the waves in complete darkness. They rely on sound.

A killer whale (orca) is pictured in the fjord of Skjervoy, northern Norway, on November 26, 2021. – Between October and February, Orcas and Humpback whales hunt atlantic herrings to build their stock of protein. PHOTO BY OLIVIER MORIN/GETTY IMAGES 

Dr. Wieland Shields said: “Protecting habitats is a key component of endangered species recovery.

“But to be biologically meaningful, any geographic or temporal protection zones need to overlap in space and time with how the target species is currently using the habitat, rather than based on historic trends.

“This study fills that data gap by demonstrating how these endangered orcas are utilizing the Salish Sea over the last five years and how that has shifted from previous trends.”

Previous studies have documented how new behaviors spread among killer whales over time through cultural transmission.

Orcas are the iconic great white shark’s only predator apart from humans. The huge marine mammals can reach up to 30ft in length and weigh over six tons, feeding on fish, squid, seals and sea birds.


Produced in association with SWNS Talker

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