Dr. Lance Barrett-Lennard says he fears changes in the ocean environment are prompting odd behaviour and an unusually high mortality rate.
Barrett-Lennard says the southern resident orca pod, which is found in the Salish Sea between Vancouver Island and the B.C. mainland, has lost seven matriarchs over the past two years, and he's noticed a lack of vocalizations from the normally chatty mammals.
The Vancouver Aquarium's cetacean research team says the whales were also seen the past two summers travelling in small groups, further offshore to find food - behaviour more typical in winter than summer.
At the same time, the researcher says the number of normally transient killer whales has been increasing over the past 25 years.
Barrett-Lennard says the changes are striking and need further study.
The alarming observations come on the heels of a study revealing that the number of killer whales in Puget Sound is dwindling - especially among reproductive age males.
Bruce Stedman, who heads up the Orca Relief Citizens' Alliance, says numbers from the Center for Whale Research and NOAA show the number of reproductive-age males is down 26 percent since 2009, and there are only 14 reproductive age male orcas left.
And he worries if those numbers don't get better soon, the result could be devastating.
"Slowly but surely, they would go extinct," Stedman said. "That's the worry."