India, Sept. 22 -- Fat Bear Week 2025 begins on September 23 at Katmai National Park and Preserve in Alaska. Fans from around the world cheer on the park's brown bears in a March Madness-style bracket, voting for which bear should advance in each round. Last year, over one million votes were cast.

In late summer and early fall, bears enter hyperphagia, a time when they eat nonstop to prepare for hibernation. "They can't feel full no matter how much they eat, so they just keep eating," says Sarah Bruce, a park ranger at Katmai. For female bears, this weight gain is crucial for successful pregnancies. "A fertilized egg won't even implant unless the mother is fat enough," Bruce explains.

According to USA Today, Katmai's brown bears depend ...