Learning from Bigg’s
Bigg’s Killer Whales (Orcinus orca), the marine-mammal-eating ecotype of orca in the North Pacific, are apex predators in the Salish Sea. Unlike their fish-eating relatives that specialize in Chinook salmon, Bigg’s target harbor seals, sea lions, and porpoises. Their hunting events are rarely observed in detail, making direct encounters a valuable opportunity to understand predator-prey dynamics.
One such event unfolded just minutes from the dock. A pod of Bigg’s orca had isolated a harbor porpoise (Phocoena phocoena), initiating a high-speed pursuit. Harbor porpoises are smaller and less powerful swimmers than orca, but they rely on extreme maneuverability to evade predation. For nearly ten minutes, this individual executed rapid, last-second turns to avoid capture. Despite its efforts, the sustained chase ultimately exhausted the porpoise, and the pod succeeded in making a kill.
Killer whales are selective feeders, with prey preferences shaped by ecological specialization. Fish-eating ecotypes, for instance, are known to consume only large salmon, while some populations have been documented removing the livers of sharks and discarding the rest. Bigg’s display a similar selectivity when feeding on marine mammals. Their focus is on blubber, a dense, lipid-rich tissue that provides insulation and serves as the most energy-dense macronutrient available. Blubber offers more than twice the caloric value per gram as protein or carbohydrate, which is critical for whales that may swim up to 80 kilometers in a single day while maintaining stable body temperature in cold marine environments.
The aftermath of the hunt illustrated this dietary specialization. While the orca consumed the blubber-rich tissues, the heart and lungs of the porpoise were left to float at the surface. Lungs, with a volume of roughly 5 liters in porpoises (comparable to ~6 liters in humans), are naturally buoyant. Their presence highlighted the precision of the orca’s feeding behavior, as lean organs provide little nutritional value compared to fat.
Predation events such as this provide rare opportunities to study both the mechanics of orca hunting and the ecological significance of their selective feeding. Observations confirm that Bigg’s orca maximize energetic gain by targeting blubber while minimizing time spent handling prey, a strategy well-suited to their high-energy lifestyles.
