Researchers at UBC are getting a rare glimpse of the social behaviours and hunting habits of resident killer whales with the help of aerial drones.
For three weeks from late August to early September, UBC researchers in partnership with the Hakai Institute used drones to monitor northern killer whales in the Salish Sea and off the central coast of BC. In using the drones, the research team lead by Director of the Marine Mammal Research Unit (MMRU) at UBC’s Institute for Oceans and Fisheries Andrew Trites seeks to determine if there is a shortage of prey for southern resident killer whales.
This study marks the first time that aerial drones were used in collaboration with multi-frequency echo sounders — sophisticated fish finders similar to those found on any commercial or recreational fishing boat — to collect data on the whales. In using these two technologies, the depths and abundance of fish in an area are able to be measured in unison with the whales’ diving behaviours and any hunting or successful prey capture events.
The footage gathered includes scenes of two killer whales diving underwater, a pod in Blackfish Sound and a mother with her female calf.
The results from this study will be used to better inform conservation efforts for the endangered southern resident killer whales, whose population has dwindled to under 75 individuals.
The northern killer whales seen in the footage have an apparently healthy population of over 300 individuals. The study was designed to be comparative in nature, with the northern residents being the control for the southern whale population, who are in worse condition overall.
“By simultaneously recording information about their feeding behaviour and their foraging successes, we can answer the question about whether southern residents are less successful at feeding compared to northern residents,” said postdoctoral fellow at MMRU and leader of the drone portion of the study Sarah Fortune. “And if they are less successful than the northern residents, is that a function of the prey that’s available to them? Are there fewer fish available to them than the northern residents, or are the fish found at deeper depths and so they become less accessible for foraging?”
Research associate at MMRU Mei Sato has previously been mapping the prey field of northern and southern residents using multi- frequency echo sounders and has successfully mapped where salmon — particularly Chinook salmon, the whales’ preferred prey — are found and in what abundances. What has been missing is information on the whales’ behaviour relative to the prey fields.
“An interesting observation that we made for southern residents was that the whales were actively foraging on surface aggregations of salmon and they had confirmed captures of Chinook salmon at the surface,” said Fortune. In using both drone technology and sonar equipment, the research team garnered a more informed understanding of what salmon abundances and prey conditions are required to support successful feeding for the southern residents.
The project is part of the federally-funded Whale Science for Tomorrow initiative. The collaboration provides funding to university-based research on the health and stressors affecting endangered whales in Canadian waters and will be used to better inform decision making in regards to fisheries management and whale conservation.