It's not easy to get to their home on the Alaska Peninsula, and fewer than 25,000 visitors made the trip last year, compared to more than 14 million at America's most visited national park, Great Smoky Mountains.

But travelers who make the trek are in for a treat.

But travelers who make the trek are in for a treat.

"You can see bear behaviors like you would never even imagine," said Keith Moore, an interpretive park ranger at Katmai.

"You could spend a lifetime in Yellowstone and still not see as much bear behavior as you could here in just a season."

The bounty of sockeye salmon running in the Brooks River starting in late June and July creates an extraordinary scene around Katmai's Brooks Camp.

More than 40 bears can be seen along the 1.5-mile river at the same time, with around 60 spotted simultaneously several years ago, according to Moore.

Fat Bear Week is a March Madness-style bracket challenge that pits some of the biggest bears along the Brooks River against each other in the arena of public opinion.

"It really started out as just celebration of this transformation that our bears go through," Moore said.