A research team led by scientists from the University of Washington and the National Oceanic and Atmospheric Administration (NOAA) has uncovered new insights into the diet of resident killer whales, which could aid in the conservation of endangered populations.
The study, published on Sept. 18 in Royal Society Open Science, examined the dietary habits of two groups: the Alaska resident and southern resident killer whales.
While both populations prefer salmon, they differ in the types of fish they eat and when they switch species, providing critical information for understanding why some populations thrive while others struggle.
Researchers found that southern resident killer whales, primarily located in the Salish Sea, face a lack of food, particularly Chinook salmon, which has been impacted by human activities such as pollution, dam construction, and noise pollution from cargo vessels.
This population, now critically endangered with around 75 individuals, contrasts with Alaska’s resident killer whales, which number in the thousands and are growing.
The study revealed that while Chinook salmon remains a key food source for all resident orcas, Alaska residents also rely on other fish species like chum, coho salmon, and even flatfishes such as arrowtooth flounder.
This more diverse diet could be one factor helping the Alaska population thrive.
These findings will help inform conservation efforts to protect endangered southern residents, by providing a more complete understanding of their dietary needs.
The research highlights the need for a broader ecosystem approach to support these whales’ recovery.
The study also involved a decade of fecal DNA analysis from both populations to determine their food sources, shedding light on seasonal diet variations and revealing a more complex picture of killer whale foraging habits than previously thought.