Troublesome black bears exiled to backwoods areas return home or die trying, a recent study finds, and some wildlife biologists say bear-resistant trash containers -- not relocation -- may be the only cure for a growing problem.

People and bears -- as many as 30,000 in California -- run into each other these days in campgrounds and neighborhoods springing up in mountainous areas. Yosemite National Park reported 214 human-bear encounters in the first half of this year, a 149 percent increase over the same period in 2003.

When bruins pillage ice chests, harass campers or bust car windows, they often get a tranquilizer dart and a one-way ticket out of Dodge. Or so scientists thought until two Nevada researchers discovered that transplanted bears didn't stay put in their new digs.

Carl Lackey, a biologist with the Nevada Department of Wildlife, and University of Nevada researcher Jon Beckmann, now with the Wildlife Conservation Society, captured eight bears in the Lake Tahoe basin between 1997 and 2002, moved them to the Sweetwater Range and the Pine Nut Mountains in western Nevada and tracked them using radio collars. Seven returned to the Tahoe basin within 18 days, and the eighth was struck by a car.

Their study, published in the May issue of the journal Western North American Naturalist, challenges animal relocation, the most common nonlethal method of managing pesky animals. Other studies have reached similar conclusions

"Relocation doesn't work," Lackey says. "Nine times out of 10, they're back at the capture site in weeks, or die trying to get home."

The studies persuaded Nevada wildlife officials to relocate bears only in rare instances.

Close encounters imperil bears. U.S. Forest Service officials destroyed a sow and her cub in July after the cub jumped a Boy Scout to get snacks in the youth's backpack. A few weeks later, Department of Fish and Game personnel destroyed a bear after it bit a hiker near Pothole Lake in the Sierra. .

Authorities have killed 94 bears in the last four years on the California side of Lake Tahoe, says Ann Bryant, director of the Bear League, a Homewood, Calif., conservation group. "People leave food outside for the cute cubs," Bryant says. The bears know "a garbage can or open kitchen door is a lot easier than getting grubs from under a tree stump."

The two Nevada scientists have concluded that bear-resistant trash containers best protect animals from self-destructive behavior, but they cost $400 to $1,200.