By LISA W. FODERARO

NORTH ELBA, New York - It was built to be impenetrable, from its “super rugged transparent polycarbonate housing” to its intricate double-tabbed lid that would keep campers’ food in and bears’ paws out.

The BearVault 500 withstood the ravages of the test bears at the Folsom City Zoo in California. It has stymied mighty grizzlies weighing up to 455 kilograms in the backcountry of Yellowstone National Park in Wyoming.

But in one corner of the Adirondack Mountains, campers started to notice that the BearVault, a popular canister designed to keep food and other necessities safe, was being compromised. First through circumstantial evidence, then from witness reports, it became clear that in most cases, the conqueror was a relatively tiny, extremely shy middleaged black bear named Yellow-Yellow.

Some canisters fail in the testing stage when large bears are able to rip off the lid. But wildlife officials say that Yellow-Yellow, a 57-kilogram bear named for two yellow ear tags that help wildlife officials monitor her, has managed to systematically decipher a complex locking system that confounds even some campers.

“She’s quite talented,” said Jamie Hogan, the owner of BearVault, based in San Diego. “I’m an engineer, and if one genius bear can do it, sooner or later there might be two genius bears. We’re trying to work on a new design that we can hopefully test on her.”

There have been no reports of the BearVault being regularly broken into anywhere else in America.

Bears and campers do not usually interact, and when they do it is usually over food.

The BearVault 350 and 400 models can be opened by pressing a tab that allows the camper to screw off the lid. But reports began coming in from campers a few years ago that BearVaults were being broken into. State wildlife officials began suspecting Yellow-Yellow, one of a number of bears they have tagged and tracked as a way of studying the behavior of bears in the Adirondacks.

In most BearVault break-ins, Yellow- Yellow’s radio collar indicated she had been in the area. Campers began spotting her from afar rifling canisters. There have been no reports of her threatening anyone.

So last year Mr. Hogan introduced the 450, a one-kilogram cylinder costing about $60, and a larger version, the 500, each with a second tab. On them, a camper must press in one tab, turn the lid partway, then press the second tab to remove the lid. But Yellow-Yellow figured that lid out, too.

And she now appears to have apprentices; campers have reported seeing other bears getting into their BearVaults.

Mr. Hogan is working on a prototype of a new model, the 550, for next year. State officials have agreed to test it by filling it with food and depositing it on Yellow-Yellow’s turf. “She’s the whole reason we’re doing this,” he said.