The critically endangered Southern Resident killer whales (SRKWs) that inhabit the Pacific Coast of Canada and the United States are balancing on a knife-edge. A study published today shows a 25% chance that these iconic whales could be lost within the next 100 years. With appropriate and resolute actions, however, this risk of extinction could be significantly reduced.
An international team of renowned scientists representing academic and conservation organizations in three countries has published a peer-reviewed paper in the journal Scientific Reports evaluating the relative importance of known threats that endanger Southern Resident killer whales. This population has experienced almost no growth over the past four decades and has declined in the last two decades.
The team, whose expertise included killer whale behaviour, ecology, bioacoustics, and population biology, was led by Robert Lacy, Ph.D., Conservation Scientist for the Chicago Zoological Society, and Paul Paquet, Ph.D., from the Raincoast Conservation Foundation. Together, the team assessed the viability of this small population of genetically isolated killer whales, which subsists largely on salmon. To evaluate the severity of known coast wide threats to the population (nutritional stress, pollutants, excessive noise), the new research considered more than 40 years of data collected by the Center for Whale Research regarding killer whale survival and reproduction. Then, by simulating various combinations and levels of these threats, the capacity for the population to recover was examined under different future scenarios.
“Not surprisingly, we found that SRKWs face a highly uncertain future with a low probability of recovery under existing conditions of food availability, pollutants, and vessel noise and disturbance,” said lead author Robert Lacy. “Conversely, increasing Chinook salmon abundance combined with reducing vessel noise and disturbance significantly increases the whales’ likelihood of long-term survival, reducing the risk of extinction.”
“The noises caused by commercial and recreational vessels of all types mask the frequencies used by killer whales to detect salmon and communicate. In addition, vessel disturbance changes the behaviour of whales, which also reduces their foraging efficiency,” said co-author Christopher Clark, PhD. “Killer whales need habitat full of salmon, but they also need a habitat quiet enough to find their food. For this already food-stressed population, reduced feeding leads to lower birthrates and lower survival.”
New research shows 25% chance Southern Residents will be gone in 100 yrs without action.
“Our study reconfirms that Chinook salmon abundance has the greatest influence on SRKW population health, but also demonstrates the powerful interaction of salmon abundance with vessel noise and disturbance,” noted co-author, Rob Williams, PhD. “We found that recovery of SRKWs requires a 30% increase in Chinook salmon above average levels. Or, we could double our conservation impact by increasing Chinook salmon abundance by 15% and reducing noise and disturbance by half.”
Unfortunately, key threats to the population are predicted to increase. This includes an expected increase in noise because of increased shipping and a predicted decrease in the abundance of Chinook salmon because of climate change.
“The most important message from our study is that with appropriate and resolute actions, the chance of survival for these iconic whales over the next 100 years can be significantly improved,” said co-author Paul Paquet. “Canadians, Americans, and global citizens care about the future of these whales.” Paquet concluded.