Can a brown bear spend too much time munching on salmon?

Not in the Alaskan wilderness, where the bears at Katmai national park are unwittingly fighting for the title of the tubbiest in Fat Bear Week – the fourth annual competition to see which bear will be fattest before a half-year hibernation.

“Life as a bear is hard,” Andrew LaValle, a national park ranger at Katmai, told the Guardian in an email. “They come out of the dens in spring looking weak and hungry, and being fat in October or November is a sign of success and resilience.”

Right now, the bears are eating almost non-stop to prepare for hibernation, which lasts five to six months and sometimes longer. Brown bears need fat to survive the -35F to 50F (-37C to 10C) winters in Katmai’s mountains.

Brown bears are at the top of the food chain and will eat almost anything, though Katmai’s are especially fond of sockeye salmon. LaValle said at peak season, a bear could eat up to 30 salmon a day. “They will gorge themselves, trying to satisfy that hunger that has built up over the past half year of starvation,” LaValle said.

Fat Bear Week kicked off on Wednesday and continues through Tuesday, when a winner will emerge.

It is up to the public to decide which is the most rotund bear.

Each day, two bears are matched against each other on Facebook and the one to get the most likes is the day’s winner and advances to the next round of the bracketed competition.

LaValle said it is up to each voter to determine what makes a bear the most plump. He said: “Does that mean clearance with the ground? Number of rolls? Neck flab? It’s up to you!”

Grizzly bears at Katmai national park in Alaska. Photograph: Paul Souders/Getty Images

There are an estimated 2,200 bears at Katmai, but only 12 are featured in the competition.

This select group consists of bears who most often appear on explore.org’s live camera of one of the park’s hot spots: Brooks Camp. It’s there that people all over the world can watch the bears reach for leaping salmon in a waterfall and see cubs wrestle at the river’s edge.

Since 2012, Katmai has partnered with explore.org to share live footage of Brooks Camp to expand access to a national park that is usually only reached by plane, and sometimes by boat.

Because of the bears’ online following, Fat Bear Week voting can be a passionate affair.

“I am beside myself with grief that my two favorite bears (Otis and Beady) have to face each other so early in the brackets,” one person commented on the day one results of the 2018 competition.

“Fun day one – a bit surprising both 503 and Walker were defeated so soundly, especially 503, what more could the poor lad do?” asked another.

Voters also had encouraging words for the bears who weren’t fat enough to advance in the competition: “He [503] is huge for a bear his age and will no doubt be the biggest and fattest bear of Katmai in the future.”