Seventy-percent of pregnancies are resulting in miscarriage, estimates one study. And the scientists behind the report believe they know why:
Over the years, killer whales accumulate toxins from their food in their fat. Normally, these pesticides and chemicals, such as PCBs or DDT, have chronic effects on the whales. But in recent years something else has happened: chinook salmon—one of the whales’ most important food sources—have dwindled.
When the whales don’t get enough to eat, they start to burn their fat reserves, which releases the stored toxins into their bloodstreams. This hurts the health of the developing calf, and the effect is particularly pronounced late in the pregnancy when the fetus is growing rapidly.
“The cumulative effects of loss of food and release of toxins are the best predicators of whether or not a pregnant female will take a fetus to term or abort it,” Wasser says.
If that is right, then the only way to boost the chances that this endangered population will survive is to rapidly boost populations of their favorite food, Chinook salmon. That isn’t easy, but breaching dams where Pacific salmon spawn, allowing greater numbers to get upriver and reproduce, is one key step supported by researchers who study the Southern Resident killer whales.
NOAA disagrees, but at this point it seems clear that more radical and creative solutions are required if there is to be any hope of supporting the remarkable population of killer whales that reside in the Pacific Northwest–who unfortunately occupy a habitat that is deeply impacted by human activity from pollution, to shipping, to fishing (not to mention a decade of captures). We are responsible for their troubles. We should feel a moral obligation to do what is needed to reverse their decline.