Researchers say the population of orcas has become so inbred that they are dying younger and their population is not recovering
People have taken many steps in recent decades to help the Pacific Northwest’s endangered killer whales, which have long suffered from starvation, pollution and the legacy of having many of their number captured for display in marine parks.
While that news sounds grim for the revered orcas – known as the “southern resident” killer whales – it also underscores the urgency of conservation efforts, said Kim Parsons, a geneticist with the National Oceanic and Atmospheric Administration’s NOAA Fisheries who co-authored the study. The population is not necessarily doomed, she said.
The southern resident population comprises three clans of whales known as the J, K and L pods. They are socially distinct and even communicate differently from other orca populations, including the nearby northern residents, which are listed as threatened and which primarily range from Vancouver Island up to southeast Alaska.
At least 13 orcas died in the roundups, and 45 were delivered to theme parks around the world – reducing the southern resident population by about 40%. The brutality of the captures began to draw public outcry and a lawsuit to stop them in Washington state. For the new research, NOAA geneticist Marty Kardos, Parsons and other colleagues sequenced the genomes of 100 living and dead southern residents, including 90% of those alive now. Those whales had lower levels of genetic diversity and higher levels of inbreeding than other populations of killer whales in the North Pacific, they found.
The Alaska resident killer whale population is estimated to have doubled from 1984 to 2010. According to the researchers, the southern residents would likely be on a similar trajectory if not for their elevated levels of inbreeding.