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Inbreeding is likely a key reason why the endangered killer whale population in the Pacific Northwest has failed to recover despite decades of conservation efforts, BTA reported. 

Humans have taken many steps in recent decades to help the endangered animals, which have long suffered from starvation, pollution and the fact that many of them are captured to be an attraction in marine parks. 

So far, their efforts have had limited success and research, and the current study, published in the journal Nature Ecology and Evolution, offers a possible explanation for why.

According to its authors, because of their inbreeding, killer whales die younger and their population cannot recover.

Females take about 20 years to reach peak fertility, however, they probably do not live to that age to ensure their population growth.

Mother killer whales make a lifelong sacrifice for their sons

While this news sounds bleak for orcas, it also underscores the urgency of conservation efforts, said Kim Parsons, a geneticist with the National Oceanic and Atmospheric Administration (NOAA) and co-author of the study. 

"A population is not necessarily doomed. In fact, in most cases it is not inbreeding itself that leads to a shortened lifespan or the death of an individual. However, inbreeding makes these animals more vulnerable to disease or environmental factors. We can support the population by by maintaining the environment and giving them the best possible chance," says Parsons. 

The struggle of the charismatic killer whales, which frequent the waters between Washington state and the Canadian province of British Columbia, has been well-documented — including in 2018, when a grieving mother carried her stillborn pup for 17 days in an apparent attempt to mourn or revive it. 

The population of these killer whales, called "southern dwellers", numbers only 73 specimens. 

killer whales