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The sea lion is an adult breeding bull, probably between 9 and 13 years old, and well over 1,000 pounds.
And while he’s fully capable of making this trip, the more important question is how and why.
“For one to move 900 miles like this, it’s not unheard of.”
Michael Rehberg leads the Steller Sea Lion Research Program for the Alaska Department of Fish & Game in Anchorage. Stellers are not migratory animals, but that doesn’t mean they don’t get around.
“Sea lions are built for swimming. They have a beautiful, fusiform shape that reduces drag, and a lot of the features of their bodies and the depth at which they’re swimming in the water, is a really efficient place to be. So sea lions, even when they’re very young, can go long distances.”
Rehburg says ADF&G has tracked sea lions in Southeast as young as six weeks old making trips of seventy miles without stopping, and has recorded one trip of 1,000 miles by a ten-month-old. The animal was at sea for three weeks.
This sea lion was tagged by biologists with the Washington and Oregon departments of Fish & Wildlife at the Bonneville Dam, about 20 miles upriver of Portland, Oregon, on February 28. It was feeding on sturgeon with a group of smaller California sea lions. The technology in the tag is innovative: the sea lion is basically wearing a cell phone on its head. It’s clear, acrylic plastic, with an antenna sticking out in front, and it continuously records the sea lion’s position using gps, or the global positioning system, data.
“And when the tag gets in range of cell towers, it’ll make a phone call and download as much data as it’s got, up to the people who are tracking it.”
Rehberg says this type of tag is really effective along the more-densely populated coast of Washington and Oregon. In Alaska, not so much. Researchers lost track of the sea lion somewhere north of Vancouver Island.
“Until it called in from Sitka, and actually someone saw it out on the water.”
That person notified local marine mammal biologist Jan Straley, who in turn notified ADF&G.
Rehberg says it’s no accident that the sea lion is in Sitka. The Sound is wall-to-wall herring right now, and he literally made a beeline here the moment biologists on the Columbia River released him. Rehberg believes these older, larger animals can develop a specialized foraging strategy that puts them where the best food is, at the best times. A biologist in Rehberg’s office has just returned from a trip to Dry Bay near Yakutat, where 2-3,000 sea lions have converged on a large-but-brief eulachon run there. She identified the tags of animals born in Washington, Oregon, and Kodiak.
“Well, they’re animals and they can move, and they know where the good food is. The main question for this guy from Oregon is: We don’t know where he was born yet. So what we really don’t know is if this is an Alaska breeding male who went down to Oregon for an easy meal, or if this is an Oregon male who came up to Alaska looking for love in the breeding season this summer.”
And if this latter is the case, will being one of the few sea lions with a cell phone on his head be an advantage? That’s probably better left to the sea lionesses than science.
In the meantime, Rehberg thinks this sea lion’s trip does shed more light on population dynamics. Alaska has two genetically-distinct populations of sea lions, eastern and western. In northern Southeast, two relatively new rookeries have started – with an apparent blend of the two populations. Rehberg says there’s an advantage “to being mobile.”
Note: Rehburg credits much of the information in this story to ADF&G biologist Lauri Jemison and her team on the mark-resight study, and includes the work of collaborators from Russia thru California.