It's not what backpackers and hikers want to hear - the pepper spray they count on to scare off bears may actually attract the big beasts, like catnip does cats.

The evidence, so far, is just anecdotal. But the stories are worrisome - bears chewing up plane pontoons doused with the spray and crowding into recently sprayed camp sites, U.S. Geological Survey researcher Tom Smith said.Smith discovered the attraction in November when he saw a bear rolling on a rope sprayed just a week earlier with powerful red pepper extract. He was recording brown bear activity near salmon streams in the Katmai National Park and Preserve, 240 miles southwest of Anchorage.

Intrigued, Smith jumped from his observation post and sprayed the beach with repellent. Several bears approached the beach 40 times to paw and roll in the spray.

"It's a 500-pound cat with a ball of catnip," Smith said.

For those who spend a lot of time in bear country - and that's anyone hiking in Alaska's backcountry - this isn't good news. Pepper spray is considered by many to be a good alternative to carrying a powerful shotgun. Tests have shown that it will stop a charging bear if sprayed in the bear's eyes, nose and mouth.

Nothing Smith found disputes those tests. But preventive uses of the spray - even spray residue on the can itself - can lure the huge, deceptively quick and potentially dangerous bears. On Sunday, an oil worker was killed by a brown bear that emerged from its winter den near the Kenai Peninsula.

Counterassault of Bigfork, Mont., which first marketed the spray, isn't worried by Smith's findings, said general manager Pride Johnson, though some people mistakenly treat it like mosquito spray.

"We've had some parents spray it on their children because it says bear repellent," Johnson said Wednesday. The company has begun changing the wording on its packaging to bear deterrent instead of repellent.

Smith's preliminary results should be noted by hikers and others, said Stephen Herrero, a bear expert at the University of Calgary and author of a book on bear attacks.

"They are going to have to think twice about how they store it, especially at night," Herrero said. "The big question of course is, `Do you sleep with it under your pillow?' "

Smith suggested treating a used can like food, putting it in a bear-proof container, and keeping an unused can in the tent while camping. Smith said he plans more testing next summer - and he'll continue carrying the spray.

But the evidence so far has him confident he's on the right track. He has submitted what he found for publication in the Wildlife Society Bulletin.

In the fall, he watched a float plane pilot spray his pontoons in an effort to keep bears away. The next morning, the floats were chewed up.