After spending the summer in his research vessel trying to track resident killer whales with a hydrophone off B.C.’s Central Coast, Vancouver Aquarium cetacean researcher Dr. Lance Barrett-Lennard was struck by the silence.
Resident killer whales are typically very chatty in the summer but, for the second year in a row, Barrett-Lennard has found them to be remarkably quiet. So quiet, in fact, that he often had difficulty finding them.
The lack of vocalizations was just one of three “puzzling” changes observed by the Vancouver Aquarium’s cetacean research team this summer. The large, fish-eating mammals were also seen travelling in small groups and travelling further offshore to forage—behaviour that is typically seen in the winter rather than in the summer.
According to Barrett-Lennard, a number of changes within the resident killer whale pods, as well as in their wider environment, may be affecting their behaviour. Over the past two years, the resident killer whales off B.C.’s coast have lost seven matriarchs, the family leaders, which is an unusually high death rate. Normally, the pods only lose one or two matriarchs every couple of years.
At the same time resident killer whales are exhibiting peculiar behaviour, sightings of Bigg’s (also known as transient) killer whales are on the rise. Over the past 25 years, Barrett-Lennard and colleagues at Fisheries and Oceans Canada noted a substantial increase in sightings of Bigg’s killer whales, which are the mammal eaters. In 1990, resident killer whales were sighted much more frequently than Bigg’s killer whales off the coast of B.C. Today, the numbers are close to equal.
Dr. Barrett-Lennard says it’s unclear if the loss of so many matriarchs or the increase in Bigg’s killer whales is having an impact on resident killer whale behaviour, but given that this is a significant behavioural change, he says it certainly begs an explanation.
Vancouver Aquarium B.C. Cetacean Sightings Network
The Vancouver Aquarium’s B.C. Cetacean Sightings Network collects data on cetaceans and sea turtles in British Columbia in collaboration with Fisheries and Oceans Canada. Public sightings are reported by residents, boaters and professionals and are used to inform research, conservation and recovery actions. Report your sighting to 1 866 I SAW ONE or email@example.com. www.wildwhales.org