Killer whales in Norway have long been assumed to just eat fish, with research focusing on the large numbers of killer whales that gather in the winter months to feed on overwintering herring in the northern Norwegian fjords. Field observations by marine biologist Eve Jourdain from Norwegian Orca Survey (NOS), however, suggested that killer whales eat a much more diverse diet, including other marine mammals such as seals. This was the start of Clare’s master thesis, which had Katrine as the main supervisor, and co-supervisors Eve Jourdain (NOS), Anders Ruus from NIVA and Jan Ludvig Lyche from the Norwegian University of Life Sciences.
The first objective of Clare’s master thesis was to investigate the extent of dietary preferences in the population, using stable isotope analysis to map out the isotopic niche. The results from this study were published in April. The second objective was to quantify levels of pollutants in the two groups of whales, and compare them to threshold levels for health effects. These are the results that are now published!
Our main findings were that the seal-eating whales had higher levels of all pollutants than the fish-eating whales. In addition to looking at levels of legacy pollutants, this is the first study to document the presence of unregulated chemicals, like the emerging brominated flame retardants PBEB, PBT and HBB in this apex predator. We are also the first to quantify mercury from skin samples in killer whales, which can give an indication of the health status for individuals and the population.
More information about the background of this project can be found in our “Behind the paper” blog post on the Nature Research Ecology & Evolution Community.
It has also been published in the University of Oslo Titan blog
Clare also presented this research at the recent SETAC SciCon digital conference, watch the whole video presentation below!