Sea lions all aboard for research
Two years ago, scientists with the Alaska SeaLife Center set up a special platform in Alaska's Resurrection Bay, hoping that sun-loving sea lions would willingly climb aboard for rest, relaxation—and research. When the animals didn't cooperate, the project seemed adrift. But this summer, some good fishing finally brought the animals on-board.
Scientists at the center brought the platform to Alaska in 2003 in cooperation with the National Oceanic and Atmospheric Administration (NOAA), as a new way to capture and study members of the endangered western stock of Steller sea lions with minimal impact on the animals.
[Read more at Alaska SeaLife Center]
The platform, designed to reduce human-animal contact, is a 20-foot square of concrete mounted atop a buoy system that allows it to float in Resurrection Bay near Seward, Alaska. Sea lions are known to climb out of the water to haul out on any convenient object, so researchers expected that the research station would attract their interest. A similar approach has worked studying California sea lions, a related species, in British Columbia and Washington state; Steller sea lions, also known as Northern sea lions, are the largest sea lion species in their family.
Like their counterparts elsewhere in the Pacific Northwest, Alaska’s sea lions love to climb out of the water to lounge in the sun, a behavior called “hauling out”.
Steller sea lions have been a major focus of research in Prince William Sound since they were placed on the endangered species list several years ago. Marine biologists at the Alaska Sea Life Center and elsewhere are very concerned about the fate of these animals because they are a key species in the ecosystem. Declining populations of sea lions and other endangered species indicate that the environment as a whole is under pressure.
But one quandary of studying such endangered animals in the wild is that, in order to learn why the species is declining, scientists must capture animals or sedate them with immobilization drugs in order to obtain blood samples, implant tracking devices or conduct other research activities—activities that might cause more stress to an already burdened population.
With the help of the floating platform, researchers envisioned doing work without disturbing normal behaviors of sea lions, said Brendan Smith, Research Education Coordinator for the center. “We don’t have to disturb the haul-out to do this,” he explained. “We wouldn’t be altering any natural, social behaviors on the haul-out or rookery.” Cages mounted atop the platform are used to trap the sea lions so that researchers can conduct their tests quickly and then set them free. The method drastically reduces the time spent in human contact, sparing the sea lion’s natural rookeries from the stress of human visitors.
Alaska’s sea lions, however, did not cooperate until the researchers involved in the project had begun to talk about scrapping the project entirely. For two years the platform remained empty, despite repeated efforts by scientists to entice them to visit it. Spencer and assistant Justin Jenniges tried a number of different cues, using sight, sound and smell to convince the animals that the platform would be a good place to stop and take a rest.
“We even set up a Steller sea lion decoy, for a visual cue,” said the Sea Life Center’s Steller sea lion field coordinator Greg Spencer.
Then, during a regular daily observation of the platform, the researchers got a welcome surprise: The platform was crowded with so many sea lions it looked ready to tip over.
“One day we pulled out our binoculars and we noted that there were about 20 Steller sea lions that had hauled out on to this buoy system,” said Smith.
Why the platform suddenly became appealing is unclear. But Spencer thinks that the most likely explanation was a large run of fish in the area that coincided with the sea lions’ visit to the platform. “It was the right combination of circumstances,” he said. The timing of the fish run and specific olfactory and audio cues likely made the platform a convenient and non-threatening location for the sea lions to take a break from their fishing.
Steller sea lion field coordinator Greg Spencer isn’t sure why Alaska’s sea lions reacted differently to the platform than animals elsewhere, but he said the different habitats frequented by the animals may account for the difference. “California sea lions haul out on sandy beaches and are pretty active when they’re out of the water,” he explained, “but Steller sea lions prefer rocky beaches and don’t move around much outside the water.”
Now that Alaska sea lions have finally given the platform their seal of approval, researchers are developing a mobile version that will make it easier to take advantage of changing circumstances such as an opportune fish run, Spencer said.
--Katherine Leitzell, Special to Alaska Science Outreach
Photo by Brendan Smith, Alaska SeaLife Center, NMFS 881-1168
Photo by Brendan Smith, Alaska SeaLife Center, NMFS 881-1168 | Posted 09.09.05 at 11:40 pm