Predator vs. prey show offers unique orca viewing

Posted: Friday, April 30, 2010

Wildlife-watching cruises are always a bit of a lottery, in terms of what one gets to see. Sometimes there is lots of action, but sometimes it's pretty quiet out on the water.

Photo By Jos Bakker
Photo By Jos Bakker

The recent Audubon-sponsored cruise to Berners Bay was no exception. We churned north past Benjamin Island and the Steller sea lion haulout. We saw humpback whales gliding around the waters near Mab Island. Arriving in Berners Bay, we found it almost empty. The hooligan run seemed to be over, the attendant hordes of gulls and eagles were nowhere to be seen, and there were no gangs of seals of sea lions hanging around. Ho-hum.

Then we noticed some thrashing and splashing in another part of the bay. A skiff was floating ever so quietly nearby. As we approached the commotion, we began to see the cause: a pod of orcas was attacking a large sea lion! Why this sea lion was up in the bay by itself was not clear, but the orcas were certainly happy to find it.

I'm not sure how many orcas were there; they were moving around so much, it was hard to tell. But there was at least one male, along with several females and several young ones. Apparently, the females were teaching the young ones how to take down a sea lion. The females would bump and push the sea lion, and then the young ones would do the same.

In part because this was a training session, the process took some time. The sea lion's head would emerge from the water, only to be forced under again. After many long minutes, and many orca lunges, we saw the sea lion no more. The orcas were grabbing their meal underwater.

During this entire affair, the orcas were frequently tail-slapping and occasionally breaching. These behaviors are thought to be a form of communication among members of the pod. Old lore suggests that tail slaps are a way to stun fish, but these orcas were transients, typically feeding on mammals, so it was clear they were not resident fish-eaters, and they were definitely not fishing! (Apparently even the tail-slaps of humpbacks are also for communication, not for stunning their forage fish.)

When it was over, the orcas swam under the boat and went on their way. At least one of them breached again. Breaching is said to be unusual for orcas, and the meaning of this behavior is not clear. Then the clean-up crew arrived: dozens of gulls moved in, picking up leftover bits and pieces of sea lion and fish that had not been eaten.

The unfortunate sea lion lost its lottery in a big way, but the orcas and gulls were winners. The human observers certainly got their money's worth in a rarely seen encounter of predator and prey.

• Mary F. Willson is a retired professor of ecology.

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