New study reveals more action is needed to save endangered Southern Resident killer whales
Authors of the study coin the term ‘bright extinction’ as they characterize the failure of Southern Resident killer whales to recover despite being the best studied cetaceans in the world.
Raincoast, in collaboration with a team of international scientists, authored a new study on the potential to recover the critically endangered population of Southern Resident killer whales. This study updates an analysis undertaken 8 years ago, which estimated the population of 80 killer whales had a 24% chance of extinction within 100 years.
The updated study, “Warning sign of an accelerating decline in critically endangered killer whales” published this week in Communications Earth and Environment, employs a Population Viability Analysis to assess how factors like the age of females, calf survival rate, and salmon abundance affect recovery of the population. The study was conducted on a population of 74 individuals.
“We explore the consequences to Southern Residents from three well documented primary threats; prey limitation (Chinook salmon), underwater noise that disrupts successful foraging, and accumulation of contaminants,” said Raincoast co-author Dr. Paul Paquet. “We found that over the next 100 years, the population will likely decline between 1% -2% annually under the current habitat conditions. While initially slow, this rate of decline increases after two generations, about 40 years, a pattern typical of populations headed towards extinction.” concluded Paquet.
The authors determined that habitat degradation through underwater noise, high concentrations of industrial chemicals, and declining quality and quantity of Chinook salmon still inhibit population recovery.
“These urban whales must find food in busy, noisy and polluted waters”, commented co-author Dr. Peter Ross and Healthy Waters Director at Raincoast. “It seems as though every time we deal with one harmful industrial chemical, we have a thousand new ones to consider. Southern Resident killer whales keep reminding us about the need for a true ecosystem approach.”
In addition to the updated understanding of threats the team also identified a phenomenon they call ‘bright extinction’ to signify a precipitous decline in a well understood population. ‘Bright extinction’ contrasts with ‘dark extinction’, the loss of species that are poorly studied and data limited,” said co-author Misty MacDuffee, Wild Salmon Program Director at Raincoast.
“The failure of the Southern Resident killer whales to recover can be attributed in large part to a reluctance to make difficult decisions”, continued MacDuffee. “In a declining population, however, the greater the lag time between knowledge and mitigation, the more draconian the recovery actions needed. Ultimately, such actions often come with a higher social cost, and with increased risk that threat reduction efforts might not work” she concluded.
In the end, the team concluded that 11th hour recovery is still possible, but more serious conservation efforts will be required.
About Raincoast
Raincoast is a team of conservationists and scientists empowered by our research to protect the lands, waters and wildlife of coastal British Columbia. Raincoast has been undertaking research, publishing rigorous, peer-reviewed science and advocating conservation action for Southern Resident killer whales since 2008.
Backgrounder: Warning signs of accelerating decline in endangered killer whales
Bright Extinction
Within the planet’s current 6th mass extinction, the term ‘dark extinction’ has been used to describe the loss of species that are data limited and poorly described. ‘Bright extinction’ is the opposite of this phenomenon. Southern Residents are one of the world’s most data rich cetaceans with federal legislation protecting them in two countries.
Recovery potential
Of concern in our updated study, we found lower recovery potential than previously estimated in 2017 due to fewer breeding females, the loss of individuals to ship strikes, inbreeding, and a reduced ability of Chinook salmon abundance to affect birth rates. This means that great efforts to recover the population will be required than if actions were taken a decade earlier.
Although no single scenario can help Southern Residents reach the US recovery objective (2.3% growth rate over 28 years), concerted efforts can halt and reverse the decline and possibly reach a 1% annual rate of recovery. In a population of 75 individuals, a single birth or death represents an annual growth or decline of 1.4%, underscoring the value of maximizing the survival of each individual.
We identify actions for SRKWs to attain a 1% population growth, which address the three primary threats facing killer whales. Additional actions that lead to a recovery in primary prey (Chinook salmon), reduction of noise, and diminished releases of harmful contaminants into salmon or whale habitat are urgently needed.
Our analysis showed that the action with the greatest leverage to recover SRKWs is their access to Chinook salmon. Although salmon recovery alone did not result in a fully recovered SRKW population, all successful mitigation scenarios included ambitious salmon management. Ensuring more Chinook are available to whales doesn’t require producing more hatchery salmon. Accordingly, our recovery scenario focused on management that changes how and where Chinook fisheries occur and the age structure of their populations.