Juneau -- A thin salmon run at a Juneau area creek has black bears turning to another food source.

Naturalists at Mendenhall Glacier Visitor Center say black bears used to eating salmon in Steep Creek near the glacier are supplementing their diets with northern ground cones.

The bears carve large swaths of dirt to reach the parasitic plant, which grows on the roots of alder trees.

"Bears are very focused on this as a food source," said Laurie Craig. "They've been supplementing on (ground cones) when the fish have been gone, which puts them right beside hiking trails."

For the past five weeks, black bears have been leaving scars in the ground that are 3 inches deep and up to the area of a king-size bed, Craig said. The bears are not spooked easily by hikers.

It's the first time in recent memory that the bears have been seen eating ground cones near the glacier as a major source of their diet, she said.

"It's obviously a really good food source because they look like they are grazing cows," she said. "The bears are all looking fat and healthy with shiny coats, so it must be pretty good."

Northern ground cones, or Boschniakia rossica, are parasitic plants that do not grow chlorophyll but sap energy from a host, such as alder, cottonwood and birch trees. They look like thin pine cones that are about the diameter of an average thumb. They typically grow about 8 inches tall in the Juneau area.

Ellen Anderson, botanist for the Juneau Ranger District, said ground cones often grow in patches and can be seen along trails. They are not on the top of most botanists' lists of plants to study, she said.

"The roots is where all the nutrients would be stored," she said. "The flowers are where the seeds would be produced. It's kind of like a potato, I guess. The energy is in the root."

Anderson said she has not heard of bears using ground cones as a major portion of their diet.

"I thought they must be pretty hard up because I hadn't noticed patches being dug up before," she said. "But these would be pretty filling, I would think."

Pete Schneider, a fisheries biologist for the Juneau Ranger District, said the small number of fish in Steep Creek has made the bears more resourceful.

"I'm sure the fish is probably, I would think, a much more desirable food source than ground cones," he said. "But they're omnivores, so they are going to make do with what they've got."

Schneider said the small number of returning coho this year is making the bears less wasteful.

"What we're seeing, at least this year, is the bears are devouring a lot of the carcasses completely," he said.

The bears are picking the carcasses clean and leaving only the nonedible parts, which are left strewn across trails, he said.

"They seem to like the live fish when they have the choice, but now we're only finding the uneatable parts," said Craig. "But then again this is the time of the year when they are really trying to pack on the extra weight in preparation for denning. So that's why they are eating the whole fish."