Up to 69% of all detectable orca pregnancies are unsuccessful. Humans might be to blame. Photo: MaxPixel

The Inertia

The southern resident orca (I hate the name “killer whale”) is having a serious problem right now. This particular kind of orca is the only type currently on the endangered species list. A big reason for this is that these mammals see more than two-thirds of their pregnancies fail. Scientists have been studying this phenomenon, examining the rate of pregnancy failure within the southern resident orca population between 2008 to 2014. “Up to 69% of all detectable pregnancies were unsuccessful; of these, up to 33% failed relatively late in gestation or immediately post-partum, when the cost is especially high,” it says in the study published in the PLOS One journal.

The study aimed to find the cause or causes of the alarming rate of pregnancy failure among these orcas, and it concluded that it’s the animals’ food source that is the central issue. Southern resident orcas depend on salmon for 97 percent of their diet, 78 percent of which consists of Chinook salmon. The Chinook salmon population has been in serious decline because of, you guessed it, human activity.

“Unfortunately, overfishing, climate change, and damming of large, coastal rivers all threaten Chinook salmon, and several populations are critically endangered (very highly vulnerable to extinction) or even extinct,” reports Oceana’s website. “Dams that prevent this species from reaching its preferred spawning grounds are probably the most detrimental human impact on Chinook salmon populations.”

It makes sense. If the salmon can’t reproduce, the salmon population is going to decrease. Sprinkle in some overfishing and you’ve got a serious decline. The orcas have less access to their natural diet, and now they have pregnancy issues. The decline of one population results in the decline of another. It’s the food web at its best, or worst perhaps.


“Low availability of Chinook salmon appears to be an important stressor among these fish-eating whales as well as a significant cause of late pregnancy failure, including unobserved perinatal loss,” the study published in PLOS One says.

It feels like a lot of the articles I write about the natural world end up pegging humans as the cause of some problem. Sometimes I feel like Agent Smith from The Matrix was right when he said, “Every mammal on this planet instinctively develops a natural equilibrium with the surrounding environment, but you humans do not. You move to an area and you multiply and multiply until every natural resource is consumed. The only way you can survive is to spread to another area. There is another organism on this planet that follows the same pattern. Do you know what it is? A virus. Human beings are a disease, a cancer of this planet. You are a plague.”

But one can’t live a life of self-loathing and hating their own species, right? If we could just become more responsible and thoughtful, perhaps it wouldn’t sound so tempting.


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