Measuring Killer Whales from the Air
Vancouver Aquarium’s Dr. Lance Barrett-Lennard, and his colleagues Dr. John Durban and Dr. Holly Fearnback are leading the way on novel insights into the health of killer whales in British Columbia. For decades, the resident population of killer whales have been studied, mostly by boat-based surveys to understand their social organization, genetics and vocal dialects. However, a report published by Dr. John Ford in 2009 linked declines in Chinook salmon with higher killer whale mortality in both the southern and northern resident populations.
Ford’s paper sparked a lot of interest in the scientific community and resulted in a number of workshops and an independent scientific panel report on the effects of the salmon fisheries on southern resident killer whales. This report in turn highlighted the urgent need to understand more about which salmon runs are most important to the killer whales and earlier detection of when their health might be declining.
In order to better understand what is going on, Lance and his team are using drones to take photos of them from above. These aerial images give us a whole new perspective and allow scientists at Vancouver Aquarium to determine how healthy the population is.
Now in the 3rd year of research, Lance and his colleagues are able to assess the condition of each whale by measuring the length and width of the whales using a technique called photogrammetry. Whale condition is linked to foraging success, and so the more the residents can find Chinook salmon, the better their condition will be. What this essentially means is that we can determine how fat and healthy they are or how close to starvation they might be. This technique can even be used to identify pregnant females from as early as 5 months!
Photogrammetry by use of drones is proving to be quick, easy and reliable to detect variation in condition. The drones, all used under permit, are quiet and are flown high so as to ensure they do not disturb the whales. This technique is providing invaluable information on killer whales and it will soon also be applied to humpback whales in British Columbia.
Humpback whales suffered massive declines in numbers during the whaling period but their numbers have been making a steady come-back in the last 25-30 years. Since they show high site fidelity, it is thought that some areas may be close to carrying capacity and measuring their condition will provide scientists with information on the productivity of each site and how that impacts humpback whale condition and population size.
So far the team have collected photos from the northern resident killer whale population (August 2014 and 2015), and all of the southern resident population (September 2015 and May 2016). This summer, the team will once again be heading to both the San Juan Islands and the Johnstone Strait to photograph all the resident killer whales again to see if there are any changes in their condition.
Funding is in place to continue the project until at least the end of 2017, but Lance hopes that it will become a long term monitoring tool that will help identify when the whales are nutritionally stressed, before they begin to starve. In particularly lean years, human fisheries for Chinook salmon could be restricted in the whales’ key foraging areas to ensure their access to prey.
This research is funded by Vancouver Aquarium, National Oceanographic Atmospheric Association (NOAA), SeaWorld Bush Gardens Conservation Fund and the National Fish and Wildlife Foundation.
Written by Natalie Sanders