Should We Start Killing Orcas?

The Times Online caught my attention today with this grizzly headline:

"Killer whales face cull after finding taste for rare otters"

The article talks about a possible culling of Orcas because a few of them have taken to eating endangered sea lions and sea otters. While there's no information about exactly how close biologists or wildlife leaders might be to agreeing to such a cull, it does say that the idea is being 'discussed.' Well, if there's a debate, here's my side of it.

Of course sea lions and sea otters are important. Steller's sea lions have been dying out in the Aleutian Islands since the 1970s. Their population has plummetted an estimated 70% despite extensive conservation efforts. Since these big seals are near the top of the marine food chain, the loss of them entirely could have a devastating impact on coastal habitats. Sea otters are even more ecologically important. They're a keystone species in the kelp forests, whose foraging of sea urchins is largely responsible for the matainence of that ecosystem. Without the otters, sea urchins destroy the kelp's holdfasts and prevent new kelp from growing, decimating the habitat provided by the massive algae.

That said, a cull is simply a terrible idea. You can't just kill off the orcas that are feeding on these animals. We destroy their food resources, then get upset that they're intelligent enough to find others. What did we expect them to do?

But more importantly, we simply don't know enough about orcas to allow such a premature attack. Orcas are data deficient on the IUCN red list. And growing genetic evidence suggests that orcas may not be one species, but instead a set of similar looking species whose vocal and behavioral traits have kept them from interbreeding for tens of thousands of years. Indeed, at least three to five distinct types of killer whales are considered different races or subspecies and are well on their way to speciation. What separates these unique groups, in part, is their feeding behavior. Certain orcas feed on fish, others on marine mammals. These behaviors are central to different small groups. If we were to go and kill off the orcas that are eating the sea otters and sea lions, we'd be eliminating a unique subset of orcas - possibly, an entirely separate species - not just a few of the thousands that exist.

I find it very hard to believe that allowing a cull will even sucessfully target only those whales which feed primarily on sea otters and sea lions. The migration patters, feeding bahviors and population structure of the transient whales which do feed on marine mammals is poorly understood at best. Resident killer whale pods are already on the endangered species list due to loss of salmon, their staple food item - accidental killing of any of these whales would be devastating. Even transient killer whales which do feed on marine mammals haven't been faring that well. The AT1 population of killer whales (currently considered part of a larger population of 346 transients), numbered only 7 in 2004 and hadn't reproduced in years, and its likely that this group will go extinct on its own.

We simply can't authorize people to kill these majestic animals without more information. And it's not like we're not already doing plenty to hurt killer whale populations - we've decimated their prey species (fish and mammal), upped the noise in their feeding grounds, and tainted their food with PCBs and other toxic chemicals. A cull is a premature, drastic and crude way to attempt to protect other endangered mammals, and the odds of its success are limited at best. We don't need to kill them; we need to understand them.

(HT on the Times article from Allie)