 by Doug Schneider March 12, 2005
Mounted high on a cliff overlooking the rocks of Chiswell Island, a popular Steller sea lion rookery in the northern Gulf of Alaska, a video camera sends images of sea lions coming and going from the island directly to the Alaska SeaLife Center, some 35 miles away in Seward. It was while watching video of the rookery that SeaLife Center researcher John Maniscalco first noticed something odd about some of the sea lions. Maniscalco said, "We started seeing a few California sea lions out at Chiswell Island through our remotely operated cameras." That's right, California sea lions. As populations of native Steller sea lions decline, Maniscalco says a growing number of California sea lions are showing up on Steller sea lion rookeries and haul-outs across the state. According to his research, some 33 sightings have been recorded. And some of those California sea lions have made their way as far west as the Pribilof Islands in the Bering Sea. Maniscalco said, "That was really surprising. And what is even more surprising is that female California sea lions are getting out that far. It was previously thought that only males travel north of California, their breeding grounds. But we're seeing females up here too." Maniscalco says that there are probably more California sea lions in Alaska than official sightings would indicate. He says researchers may have overlooked some of the California sea lions simply because they didn't expect to see them so far from their normal range.
Maniscalco said, "I think your average lay person might not tell the difference between a California sea lion and a Steller sea lion. Especially the female California sea lion, which could easily be confused with a young Steller sea lion. But the adult bull is much different. They're generally darker in color and have a more dished face...but also a really bony crest on the top of their head." If the physical differences aren't enough to distinguish the two sea lion species, Maniscalco says their vocalizations are. In fact, he says, that's how one California sea lion caught his attention. Maniscalco said, "It's been much easier to tell them apart by their voice. The California sea lion has a barking sound that's the typical circus-seal bark, whereas the Steller has more of a growl sound." Scientists can't say for sure just why California sea lions are packing up and moving to Alaska, but Maniscalco believes several factors are likely at work. Maniscalco said, "Their populations are increasing in the southern breeding range. Competition factors may be pushing them north. It could be a change in the Gulf of Alaska ecosystem as well. The big shifts we've seen over the past 30 years in fish abundance and increased water temperatures may be causing California sea lions to come up this far." It's too early to say just what these sightings mean for the survival of Steller sea lions, already listed as an endangered species across much of Alaska. But Maniscalco is sure of one thing-scientists will be taking a second look at sea lions they study from now on. Maniscalco said, "For now it's just an interesting curiosity. We are going to continue to look for California sea lions."
This story is courtesy of Arctic Science Journeys. Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.
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