Killer

May 10, 2023

I came across an article in a previous newspaper (yes, I am behind in my reading) about the shorter life spans among killer whales.  The Northwest’s endangered population has long suffered with starvation, pollution, and the legacy of having many of their numbers captured for display in marine parks.  Recent attempts have been made to breach dikes and remove dams to create wetland habitat, and limiting commercial fishing for the Chinook salmon which are important food for the whales.  Regulations have been made to slow boats down and keep them further away to avoid collisions, and reduce the stress, and quiet the waters so the whales can hunt.  So far this has had limited success, and recent research published in Nature Ecology and Evolution suggests the cause appears to be that the inbred population is dying younger, and their numbers are not recovering.

When I looked online, I found Orcas (Orcinus orca), or killer whales, almost never attack humans.  The whale’s name was originally “whale killer,” as ancient sailors saw them hunting in groups to take down large whales, according to Whale and Dolphin Conservation (WDC).  Today, orcas are recognized as among the most widely distributed mammals on the planet, occupying every ocean.  They are incredibly social, diverse, and ferocious marine predators with a diet ranging from penguins to great white sharks.  The small size and isolation of the endangered population of Southern Resident Orcas in the Pacific Northwest have led to high levels of inbreeding, and this inbreeding has contributed to their decline, even while surrounding killer whale populations expand.

 The southern resident population is composed of three clans, known as J, K, and L pods.  These clans are socially distinct and communicate differently than other populations of killer whales.  While the southern range overlaps with other orca populations, researchers say they have not regularly interbred in 30 generations.  Today, only 73 southern residents remain.  Previous studies suggested interbreeding was a problem, but this new research sequenced the genomes of 100 living and dead southern whales.  The study found lower levels of diversity and higher levels of inbreeding than other populations of killer whales in the North Atlantic.  Inbreeding has also afflicted other populations of isolated or endangered species, such as the mountain lions of California (Felis concolor), gorillas in Africa (Troglodytes gorilla), and bottle nose dolphins (Tursiops truncatus) off the coast of western Australia.  Scientists were able to improve the gene pool by introducing animals from other populations.  That is not the case for killer whales, as the southern residents already have opportunities to interbreed and have not done so.  Ultimately, it is up to the whales to mate with whom they choose. 

Thoughts:  Inbreeding in animals can result in malformations or harmful traits due to two identical alleles of a particular gene or genes (high homozygosity rate).  Having a high homozygosity rate is problematic for a population because it will unmask recessive deleterious alleles generated by mutations and may be detrimental to the survival of endangered animal populations.  Despite all its disadvantages, inbreeding can also have a variety of advantages, such as ensuring a child produced from the mating will pass on a higher percentage of its mother/father’s genetics.  Orcas are akin to humans in that they do not become fertile until their teenage years and the inbreed population has led to in a shorter life span (down from an estimated 100 to 40 years in the wild) and a resulting drop in the number of calves to replenish the population.  Selective breeding in humans is called eugenics.  Eugenics or controlling the gene pool of humans has been tried in the past, with similar results as the killer whales.  Act for all.  Change is coming and it starts with you.