Animals and Insects

Inbreeding is further endangering the population of killer whales

A report is sparking concerns about a population decline among Southern Resident killer whales due to inbreeding.

Inbreeding is further endangering the population of killer whales
Fisheries and Oceans Canada / AP

The Southern Resident killer whale population is one of the most iconic killer whale populations in the Pacific Northwest. But according to new research, this endangered species has become increasingly inbred.

Scientists have published a report in the journal Nature Ecology and Evolution detailing how extensive genome sequencing revealed the extent of inbreeding among the population.

"What we found is that there was a high degree of inbreeding in the Southern Resident killer whale population and that this is manifesting in a shortened life span for individuals, particularly for some of the females we were looking at.," said Kim Parsons, a National Oceanic and Atmospheric Administration fisheries geneticist.

Inbreeding can reportedly cut the lifespan of these whales nearly in half. As a result, scientists say the females are struggling to reach the age of peak fertility in their early 20s, opening the door to population decline.

"It's not often inbreeding itself that will result in a shortened lifespan or kill an individual; it's really that inbreeding makes these individuals more vulnerable to disease affecting their immune system, or environmental factors," Parsons said.

The entangled whale, which was initially detected south of Nantucket in February, has been identified as a female.

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According to the National Oceanic and Atmospheric Administration, or NOAA, there are believed to be only 73 whales in the Southern Resident killer whale population, which consists of three groups called pods — known as J, K and L.

The population is often encountered in the waters between Washington state and the Canadian province of British Columbia. For roughly 50 years, the population has been a longtime focus of whale advocates and scientists who have worked to address environmental stressors such as chemical pollution, noise and disturbance from ships and other vessels, and changes in the population of Chinook salmon, which is the whales' main prey. Scientists behind this report say the stressors need to be addressed if this population has a shot at stabilizing and growing.

"We can support the population by supporting the environment and giving them the best chance possible so that their body can deal with that," Parsons said.

NOAA reports that at least two offspring per female killer whale are needed in order for a pod population to remain stable or increase in number. In recent years, there have been a series of highly documented pregnancy losses and calve deaths among the Southern Resident killer whale population, further solidifying concerns for these endangered whales.