Inbreeding hurting whale population
Females dying before reaching peak fertility
SEATTLE — 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.
They’ve breached dikes and removed dams to create wetland habitat for Chinook salmon, the orcas’ most important food. They’ve limited commercial fishing to try to ensure prey for the whales. They’ve made boats slow down and keep farther away to reduce stress and quiet the waters so orcas can better hunt.
So far, the efforts have had limited success, and research published Monday in the journal Nature Ecology and Evolution suggests why:
The whales are so inbred that they are dying younger and their population is not recovering. Female killer whales take about 20 years to reach peak fertility, and the females may not be living long enough to ensure the growth of their population.
While that news sounds grim for 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.
“It’s not often inbreeding itself that will result in a shortened lifespan or kill an individual,” she said. “It’s really that inbreeding makes these individuals more vulnerable to disease or environmental factors. We can support the population by supporting the environment and giving them the best chance possible.”
The struggles of the orcas that frequent the waters between Washington state and British Columbia have been well-documented — including in 2018, when one mother carried her stillborn calf for 17 days in an apparent effort to mourn or revive it.
The southern resident population comprises three clans of whales known as the J, K and L pods. They are socially distinct and communicate differently from other orca populations, including the nearby northern residents, which are listed as threatened and primarily range from Vancouver Island up to southeast Alaska.
While the southern residents’ range overlaps with other populations of killer whales, they haven’t regularly interbred in 30 generations, the researchers said.
In the 1960s and ‘70s, dozens of Pacific Northwest whales were caught for display in marine theme parks. 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 percent. The captures drew public outcry and a lawsuit to stop them in Washington state.
Only 73 southern residents remain, according to the Center for Whale Research on Washington state’s San Juan Island.