Researchers discover orcas and dolphins hunting together to catch salmon in B.C. waters

In a world first, Canadian and German researchers have discovered that some species of orcas and dolphins team up to hunt for salmon.

The study, published in the journal Scientific Reports, was a collaboration by scientists at the University of B.C., Dalhousie University, the Leibniz Institute in Germany, and B.C.’s Hakai Institute.

Using aerial drones and bio-loggers — small devices attached to animals to record data on movement and behaviour — the researchers recorded interactions between fish-eating northern resident killer whales and Pacific white-sided dolphins in B.C. waters.

They observed frequent co-ordinated movements, with the killer whales appearing to work with the dolphins to find chinook, according to the study.

Researchers recorded reduced echolocation and rolling movements by the killer whales in the presence of dolphins, and said this shows “the whales may eavesdrop on dolphin echolocations to scan broader areas to locate large chinook salmon—prey that are too big for the dolphins to capture and swallow whole.”

Captured fish were brought to the surface by the killer whales and broken apart for sharing with pod members — while the accompanying dolphins scavenged scraps.

The study also notes that the orcas and dolphins did not appear to be fighting over the fish, rather their movement suggested co-ordinated foraging behaviour.

The scientists say more work is needed to study this phenomenon.

Lead author Sarah Fortune, an assistant professor in Dalhousie’s oceanography department, said in a statement released by UBC that researchers have known for a long time that resident killer whales interact with Pacific white-sided dolphins but seeing them dive and hunt in sync “completely changes our understanding” of these encounters.

“Our footage shows that killer whales and dolphins may actually be co-operating to find and share prey — something never before documented in this population,” she said.

The aerial and underwater observations showed that the two species frequently foraged in close proximity, and often synchronized their movements.

“The strategic alliance we observed between the dolphins and killer whales is extraordinary,” said senior author Andrew Trites, a professor and director of the marine mammal research unit at UBC’s institute for the oceans and fisheries, in the UBC statement.

Trites said by working together, killer whales can conserve energy and use the dolphins as radar-equipped scouts to increase their chances of finding large chinook at deeper depths.

“In return, the dolphins gain predator protection and access to scraps from one of the ocean’s most prized fish. It’s a win-win for everyone involved,” added Trites.

Keith Holmes, a drone pilot with the Hakai Institute, first spotted the behaviour by chance during fieldwork for a UBC-led project, according to UBC.  It was also the first time customized animal tracking solutions tags were used on whales to collect data with video and acoustics.

ticrawford@postmedia.com

Related