Eastern Canadian Killer Whales: The Great Unknown of the Atlantic

Some individuals feed primarily on marine mammals, including baleen whales, toothed whales, and seals. Others have been seen chasing schools of fish (herring, tuna) or seabirds. Lastly, a final ecotype is believed to correspond to killer whales that feed on sharks. Lawson bases this hypothesis on the study of two killer whales found in the eastern Canadian Arctic with prematurely worn teeth, a distinctive feature of shark- and ray-eating killer whales due to the rough skin and placoid scales of their prey.

In the eastern Canadian Arctic, including Hudson Bay, killer whales have been observed more frequently in recent decades. Retreating ice appears to provide them with better access to habitat and prey. These individuals feed seasonally, mainly on marine mammals such as narwhals, seals and belugas. Across the Baffin Sea, off the east coast of Greenland, killer whales feed on fish.

The latest research has identified two killer whale populations in this region. A second population appears to be found off Greenland and Iceland and possibly farther east; it is not part of the Northwest Atlantic and Eastern Arctic group. “[This population] has a mixed diet of fish and marine mammals, particularly seals,” DFO reports. However, scientists are not sure whether or not these populations interact. “Besides their genetic and dietary differences,” DFO explains, “we do not yet know whether the two populations are different in their morphology or how they communicate.”

Today, eastern Canadian killer whales are seen both singly and in small groups of three to seven individuals. These groups are smaller than those seen in the resident populations of British Columbia. Their size is more in line with that of the transient killer whales of western Canada, also known as Bigg’s killer whales. Nearly one in every four sightings of this population is of solitary individuals!

In 2013, a PhD student compiled a catalogue of 67 identified individuals, a first for this region! However, there are certainly more. “Unlike killer whales on Canada’s west coast, eastern killer whales have very few markings,” says Dr. Lawson, “which makes it challenging to identify individuals using photo-ID techniques.” Based on limited data, it is estimated that at least 160 mature killer whales roam the waters of the Gulf of St. Lawrence, Newfoundland and Labrador.

Nevertheless, DFO researcher Steve Ferguson points out that there is a photo-ID match between whales observed in Disko Bay and the Canadian Arctic, which would indicate a link between the West Greenland and Eastern Canadian Arctic (ECA) killer whales. Referred as ECAG1, this High Arctic population has been estimated to number about 200 individuals. Ferguson explains, “We included genetics from both West and East Greenland killer whales in our models and the East Greenland killer whales We believe this population is probably part of the East Greenland-Icelandic killer whales and may be related to killer whales farther east (though we didn’t have samples to verify this). If we’re right, this would be a very large killer whale population with a mixed diet of fish and seals.”

The Northwest Atlantic and Eastern Arctic killer whale population was given the status of “species of special concern” in 2008. According to the COSEWIC report published in December 2023, the main threats faced by the species are hunting, entanglement in fishing nets, as well as acoustic and physical disturbances due to increased maritime traffic and contaminants.

Killer whales in this region are overexposed to contaminants in Atlantic waters due to the fact that they are at the top of the food chain. The result is killer whales that show high levels of (in French) and DDT, substances that have been banned in Canada since the 1980s. The biopsied individuals had 100 mg/kg of lipids in their system, which is double the toxicity threshold of 41 mg/kg! Even if they haven’t been used in decades, these contaminants still persist in the environment, especially in the Great Lakes. At excessive concentrations, they affect the immune and endocrine systems, and can compromise an animal’s development and reproductive success. More attention must be paid to the environment in which this still very mysterious population lives in order to better protect it.