Inbreeding is hampering population growth for orcas, study finds

Orcas off B.C.'s coast have been critically endangered for many years, and scientists have found that a lack of genetic variability may be why. 

A new study out of Washington state, published March 23 on the journal Nature, has found that inbreeding depression — the reduced survival and fertility of offspring that are a product of inbreeding — is preventing the southern resident killer whale population from growing.

There are 73 southern resident killer whales in the waters off B.C., Washington state and Oregon, and they're all related to varying degrees — because of inbreeding. 

Lance Barrett-Lennard, a senior scientist at the Raincoast Foundation's Cetacean Conservation Research Program, says there were 71 southern resident orcas about 30 years ago.

"There was a peak of almost 100," he told All Points West host Jason D'Souza. 

"We worry about them a lot."

Barrett-Lennard, who is not connected to the study, said it's no surprise to learn that inbreeding is harming population growth, because mate choice is limited in such a small population. 

Inbreeding is considered problematic for both people and animals — less genetic diversity can weaken immune systems, increase genetic disorders and can lead to higher infant and child mortality rates. 

Conservationists have been working to save southern resident killer whales for 50 years, but the population remains fairly stagnant. 

Conservation efforts typically focus on extrinsic factors like food availability, ship noise and vessel proximity. But, as the study points out, those factors fail to account for genetic issues. 

Barrett-Lennard said the findings should encourage humans to be even more sensitive to the southern resident orcas, taking extra precautions to reduce threats like underwater noise, pollutants and competition for prey.

The study suggests that if the population remains genetically isolated and environmental conditions persist, further decline can be expected. 

Despite this somewhat grim prediction, Barrett-Lennard is hopeful.

"It means that the population's challenged. It doesn't mean that it's doomed," he said. 

"They're incredibly resilient animals. Really, you think about all the assaults they faced over the last 40 years and they're still there."