Orcas and Dolphins Form ‘Friendship’ to Hunt Salmon Cooperatively

Killer whales and dolphins collaborate to catch salmon in the North Pacific Ocean, revealing new insights into the intricate social dynamics of marine mammals.

Using video cameras and sensors attached to nine killer whales, researchers observed four of them diving alongside a large group of white-tailed dolphins towards Chinook salmon hiding in deep waters off northern Vancouver Island. An additional three whales were tracked via drone. The killer whales consumed the salmon, leaving behind scraps that the dolphins scavenged.

“They collaborated to locate food,” states Sarah Fortune from Dalhousie University, Canada. “One might anthropomorphize this scenario and suggest that they’re hunting friends.”

Chinook salmon, or king salmon, can exceed a meter in length, making them often too large for dolphins to consume.

However, the whales off northern Vancouver Island are known for their hearty appetites, frequently tearing fish apart to share with their pod, which leaves behind blood, scales, and remnants for dolphins to eat. Researchers propose that dolphins assist whales in locating salmon.

In the video, six out of twelve whales directed their attention toward the dolphins, totaling 102 interactions. The four whales dove with the dolphins to depths of 60 meters, where it becomes dark and salmon can conceal themselves among rocks and crevices.

Though both species emitted clicking and buzzing sounds, data from the sensors indicated that the whales often reduced their echolocation activity, likely to “eavesdrop” on the dolphins. Since echolocation operates like a focused spotlight, having numerous dolphins scanning the waters could enhance the whales’ chances of finding fish, according to Fortune.

“It’s akin to turning on the high beams of a vehicle; the sound serves as the light,” she elaborates.

Prior to this, scientists have noted cooperation among various species, such as fish guiding octopuses to crustaceans and nectar birds leading humans to bee colonies. However, documented interactions between killer whales and other species have often involved predatory behaviors.

Recently, killer whales were reported to have rammed and sunk six sailing vessels around the Iberian Peninsula, suggesting they may be engaging with boats rather than attacking. They are playing with them.

Brittany Visona Kelly from the global conservation group Ocean Wise asserts that the dolphins in this study are not aiding the whales but scavenging leftovers. In a study she and her colleagues, including Lance Barrett-Leonard, revealed drone footage showing whales seemingly ignoring the dolphins, playing with them, and occasionally charging at them. Their findings suggest that dolphins primarily seek refuge from a specific group of mammal-eating killer whales, known as big killer whales, which tend to avoid resident orcas.

“We found no clear evidence that these interactions benefit killer whales,” Visona-Kelly concluded.

The study reported last month indicated that between 30 to 40 white-tailed dolphins encircled an emaciated killer whale known to researchers as “I76,” who remained submerged and did not reemerge. This suggests that the dolphins may have “exhausted I76, making it impossible for him to surface.”

Luke Rendell from the University of St. Andrews in the UK emphasized that the new research provides compelling evidence of cooperation, whether the whales are interpreting dolphin echolocation or drawn to the commotion as a potential indicator of fish.

“These animals are intelligent and possess adaptable behaviors,” he notes. “We witness a range of interactions between killer whales and dolphins, from the former preying on each other to playful interactions and collaborative efforts.”