Unveiling the Astonishing Hunting Strategy of Salish Sea Killer Whales

The groundbreaking observation took place at Protection Island, a national wildlife refuge near the mouth of Discovery Bay in Washington State, in August 2016. Justine Buckmaster, a naturalist with a Washington-based tour company, had the privilege of witnessing this unprecedented event. At first, she feared that a stranded whale had accidentally beached itself, but what unfolded before her eyes was a display of calculated hunting strategy.

A group of five Bigg’s killer whales had targeted the westernmost point of Protection Island, where harbor seals and their pups were resting on a cobble beach. The group’s matriarch and a subadult male deliberately grounded themselves in the shallows, sending shockwaves of excitement through the observers. The subadult male, in particular, made several head-on charges at the shore, stranding itself on the beach. Buckmaster vividly recalls the sight, noting how the killer whale’s dorsal fin wobbled as it came to a full stop. It took powerful thrusts of the tail flukes to refloat the whale, confirming its complete grounding.

According to Josh McInnes, a biologist with the Transient Killer Whale Research Project and the lead author of the study, the killer whales’ objective was to scare the seal pups into the water, making them easy prey. While they haven’t reached the stage of grabbing seals off the beach, this hunting tactic is still in its early development.

Intentional stranding has been previously documented at sites like the Valdes Peninsula in Patagonia, where narrow breaks in rocky reefs provide killer whales access to pebble beaches, ideal for snatching sea lions from the shallows.

McInnes suggests that this behavior likely emerged opportunistically among northern hemisphere mammal hunters, much like in southern hemisphere populations. It wasn’t a learned behavior from killer whales in South America but rather an incidental trait that evolved.

John Ford, a whale researcher emeritus with Fisheries and Oceans Canada, who has studied the region’s killer whales extensively, believes that Bigg’s killer whales have been grounding themselves in shallow water while hunting seals for some time. He points out that there have been instances where individuals from the same population were stranded on rocky shorelines after hunting seals.

While the Salish Sea offers some suitable sites like Protection Island, where this behavior can be observed, it’s unlikely to become a widespread hunting tactic within the population. The scarcity of such sites limits the opportunity for its proliferation.

Nevertheless, this remarkable observation highlights the adaptability and versatility of Bigg’s killer whales as skilled predators. They have demonstrated their comfort in very shallow waters, posing new challenges for the seals of the Salish Sea. Leisurely afternoon naps on the beach may indeed become a thing of the past for these marine mammals.