Cannibalism in Orcas? The Mystery of the Bitten Fins - Orca Wars: Transient Killer Whales May Be Hunting Their Resident Cousins

Two distinct groups of orcas, known as residents and transients, share the waters off North America's west coast. They differ in diet, social structure, and even language. Now, evidence suggests that one type may be preying on the other.

In 2022, a severed orca fin found in Siberia carried bite marks matching those of a transient orca. DNA tests later confirmed the victim belonged to the resident ecotype, raising concerns about growing tensions between the two groups.

Resident orcas spend their lives in tight-knit family pods, often spanning multiple generations. They stick to coastal waters from central California up to Alaska, favouring areas like Puget Sound and British Columbia's Salish Sea. Their diet consists almost entirely of salmon, and they rarely stray from their core summer habitats.

Transient orcas, by contrast, roam far more widely. They hunt in smaller, shifting groups and target marine mammals, including seals, sea lions, and even other whales. Their range extends from southern California to the Bering Sea, often venturing into deeper offshore waters.

The two ecotypes do not mix. They avoid interbreeding, communicate differently, and even have subtle physical differences. But recent findings suggest their relationship is more than just avoidance. The 2022 discovery of the bitten fin—confirmed through DNA as belonging to a resident—points to transient orcas attacking, and possibly killing, their fish-eating counterparts.

Residents appear to defend themselves through numbers. Their large, stable pods may deter transient attacks, even when food isn't at stake. Yet the loss of a key female, such as a mother or grandmother, can weaken a pod's survival chances. Some evidence also shows residents actively chasing away smaller transient groups from their territories, hinting at an ongoing struggle for dominance.

The severed fin offers rare proof of direct conflict between resident and transient orcas. With transients expanding their range and residents already facing habitat pressures, interactions between the two may grow more frequent. Researchers continue to study how these dynamics could shape the future of both ecotypes in the region.