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Researcher Studies Feeding Habits Of Rapidly Declining Stellar Sea Lions

Date:
May 17, 2000
Source:
Texas A&m University
Summary:
The Steller sea lion could use a good PR campaign. Numbers of the relatively little-known mammal are down 80 percent worldwide, but few seem to be aware of it.
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COLLEGE STATION - The Steller sea lion could use a good PR campaign. Numbers of the relatively little-known mammal are down 80 percent worldwide, but few seem to be aware of it.

Studying the feeding habits of the creature - which may help to understand its steep decline - is the focus of a project by Texas A&M University at Galveston researcher Markus Horning and funded by the National Oceanic and Atmospherics Administration through the National Fish and Wildlife Foundation.

Horning is using three Steller sea lions at the Alaska Sea Life Center at Seward to determine the animal's diving patterns. He wants to see how the Steller sea lion can adapt when its food supply is not what it used to be.

Horning and doctoral student Leslie Cornick are using fish-feeder guns to release food at varying rates during a series of dives by the captive sea lions. By monitoring responses in the sea lions' behavior, they hope to see how the Stellers can adapt to changes in their food supply, which includes fish such as the pollock, cod and atka mackerel. The results could go a long way in determining why the Steller sea lion is down to only 20 percent of its numbers of just a few years ago.

"We're trying to better understand the diving behavior of Steller sea lions, which we have had a hard time with in relation to changes in their food supply," Horning says.

"The purpose is to simulate feeding dives with our three captive sea lions and monitor their swimming efforts. Do they dive longer when there is less fish? Does that make it costlier for them to feed themselves? If we can determine such basic relationships, then we can better understand the dive behavior of free-ranging Steller sea lions, and how this behavior might reflect changes in their food supply."

Once a familiar sight in Alaskan waters, the Steller sea lion has fallen on hard times of late, Horning adds.

The animal can still be seen along the California and Oregon coasts, and it also inhabits the Kamchatka region of Russia and Japan. But in much of the Pacific, the Steller sea lion is often a no-show.

Horning says it is the largest of all sea lions, with males averaging about 2,200 pounds.

There could be several reasons why the Steller sea lion has declined, Horning believes.

One could be overfishing, especially in northern Pacific and Alaskan waters, where the animal's food supply could be affected. Another could be predators, such as orca whales and sharks.

Pollution of the oceans could also be a factor, harming the Steller's immune system and female fertility.

"The simple fact is, there are far fewer numbers of them now than ever before and the outlook for them is not that bright," Horning adds.

"By simulating their diving and the way they go after their food, our project may tell us more about how the Steller sea lion goes about collecting its food. How accessible is its food source? Is it having greater difficulty in obtaining this food? Could that be related to fishing activities? Our tests may tell us more about its food supply and how the Steller sea lion goes about collecting its food.

"These are some of the questions we hope to be able to address with our project."

Horning says the results should be available by early next year.


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The above post is reprinted from materials provided by Texas A&m University. Note: Materials may be edited for content and length.


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Texas A&m University. "Researcher Studies Feeding Habits Of Rapidly Declining Stellar Sea Lions." ScienceDaily. ScienceDaily, 17 May 2000. <www.sciencedaily.com/releases/2000/05/000515090755.htm>.
Texas A&m University. (2000, May 17). Researcher Studies Feeding Habits Of Rapidly Declining Stellar Sea Lions. ScienceDaily. Retrieved August 4, 2015 from www.sciencedaily.com/releases/2000/05/000515090755.htm
Texas A&m University. "Researcher Studies Feeding Habits Of Rapidly Declining Stellar Sea Lions." ScienceDaily. www.sciencedaily.com/releases/2000/05/000515090755.htm (accessed August 4, 2015).

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