They now go frequently into waters they once avoided.

Killer whales have been spending more time in the Arctic Ocean due to melting sea ice. 

Killer whales (Orcinus orca) are smart and adaptive predators. They go where the food is and will team up to take down prey. They are regularly found in the waters of southern Alaska but rarely wander into the U.S. Arctic, where the water is typically covered in ice and they risk being entrapped.1

But now that there’s less sea ice in the Arctic Ocean, whales are venturing more frequently into the waters they once avoided, according to new research.1

Brynn Kimber, a researcher from the University of Washington, presented her findings at the recent 181st Meeting of the Acoustical Society of America. The abstract was published in The Journal of the Acoustical Society of America.

“Identifying the movement patterns of species is vital both in conservation, and in our overall understanding of the natural world. The Arctic and the areas around it are some of the most productive in the world, but they are also undergoing many rapid changes, so monitoring the species that live there (both seasonally and year-round) is of vital importance,” Kimber tells Treehugger.

“Killer whales have long seasonally ventured into the Arctic, typically only during the open water season, when there is no risk of ice-entrapment. As the yearly ice extent decreases, there is more opportunity for killer whales to venture further into the Arctic.”  

Unlike belugas, bowhead whales, and narwhals, killer whales have a dorsal fin. That makes it hard for them to break through ice floes to create breathing holes.2

“Without the ability to break through ice, the killer whales risk ice entrapment, where they essentially are stuck in ice cover, unable to escape until they either suffocate or starve,” Kimber says. “To avoid this gruesome fate, killer whales do not follow their prey into ice covered regions. Instead, they take advantage of the many high productivity spots in the Arctic where their prey might gather, often just around the edge of the ice floes.”

Kimber points out that killer whales are extremely efficient predators. They can have a dramatic impact on both the number of prey and on predator behavior, as other animals avoid them. That can affect how their prey feeds and raise their young, among other behaviors.2

“The potential for killer whales to disrupt Arctic food webs is definitely existent, so I wanted to follow the pattern of the whales movement to see how much of a possibility this problem might be,” Kimber says.

Trends in Killer Whale Movement

Kimber is part of a team at the Marine Mammal Lab at the National Oceanic and Atmospheric Administration (NOAA). For their research, she and her colleagues studied Arctic transient killer whales, analyzing eight years of acoustical data recorded by underwater microphones from 2012 to 2019. The microphones were placed off the western and northern coasts of Alaska.2

“Our team has over 20 recorders stationed in many seas around Alaska (Bering, Chukchi and Beaufort). As various marine mammals, from killer whales to walrus, make sounds around these recorders, we are able to compare those signals to literature documenting each animal's distinct, stereotyped calls,” Kimber explains.

“This gives us presence/absence information for each species, as well as a catalog of their calls. With this information, we can get an idea of how various species are using the ecosystems that we have the recorders moored in.”

In studying the information, she found three clear trends. 

First, killer whales are arriving earlier in the Bering Strait, where they have long been documented, in response to decreasing sea ice. Sea ice disappeared about one month earlier by 2019 at the end of the study, compared to 2012 at the start of the study. They found that killer whales also began arriving about a month earlier in response.2

They also discovered that in northern areas, such as near Utqiagvik, where killer whales have been very sparsely recorded before, there was an increase in whale calls through the years. From 2012 to 2019, the detection rate of killer whale calls tripled.2

“The third trend is that we are detecting killer whales in more northern areas than they have been recorded before,” Kimber says. “One of our recorders is in the Chukchi borderlands, and even there, we are detecting killer whales in the later years.”

Affecting the Ecosystem

With killer whales spending more time than previously noted in the Arctic Ocean, there can be all sorts of impacts on their ecosystems.

“They are very efficient predators, and can prey on a wide variety of species, from sea otters to gray whales. Some of these species are used to killer whale predation pressure, but Arctic resident species are used to having ice cover to protect themselves from it,” Kimber says.

“Bowhead whales are of particular concern, given that they are endangered and also an important source of food for subsistence hunters. Other research has seen an increase of scarring on bowhead whales as a result of killer whale attacks, suggesting that killer whales may increasingly be branching out to Arctic species as a source of food. Any changes in food web dynamics can, of course, have cascading changes in an ecosystem.”3

Fact checked by Haley Mast