Alaska’s Fat Bear week is more than a bit of fun—for the animals, size is a matter of survival

The most gripping week of the bear calendar has arrived. The Fat Bear Week is an annual online competition hosted by Katmai National Park and Preserve in Alaska. This event, which began in 2014 as a one-day celebration, has since grown into a phenomenon among bear enthusiasts worldwide.

Bears are paired in single-elimination matchups where people can read their biographies, look at their pictures and vote based on which bear “exemplifies fatness and success.” So it is not all about their size, but also about their life histories.

Why are we celebrating bear chubbiness? Because for brown bears, getting fat is a matter of survival. In just a few short months, they must bulk up to prepare for a long seasonal slumber, when they enter a deep sleep similar to hibernation (called torpor), stopping all bodily functions, including eating, drinking, and eliminating waste, while their body temperature, heart rate, and metabolism decrease.

This is especially remarkable when you consider that some Alaskan or Scandinavian bears might spend seven months in their dens. Even more impressive is that, during this period, pregnant female bears give birth, lactate and rear the extremely vulnerable cubs. This is a critical adaptation that allows bears to conserve energy during prolonged periods of harsh weather and food scarcity. So yes, those extra kilos are a badge of honor.

The bear’s bulking period is called hyperphagia, a time when brown bears become obsessed with finding the fattiest, sweetest, and most protein-rich foods.

In Europe, they switch their diet in summer to feast on fruits (especially berries), hard mast such as acorns and nuts, and also prey on or scavenge animals. But the true champions of chubbiness are the coastal brown bears of Alaska, with some individuals tipping the scales at an astonishing 650kg—more than twice the weight of their European cousins.

These giants gorge on calorie-dense salmon, targeting the fat-rich roe and brains, and can devour up to 40 fish a day. That’s a jaw-dropping intake of 20,000 to over 100,000 calories daily. The result: coastal Alaskan brown bears can gain more than 2 kg per day.

But Fat Bear Week is not just about size. Voters (about 1.2 million in 2024) are encouraged to dive into the life histories of the contenders. Their biographies reflect the harshness of the environment and the fierce competition for resources and mating success. These bears’ lives tell us stories of loss, grave injuries, and also of determination, adaptability, and perseverance.

A matter of life and death

Female bears face enormous challenges: if they fail to accumulate enough body fat, they risk losing entire litters due to the energetic demands of cub rearing. Cubs are also vulnerable to attacks from other bears, particularly males, who may kill infants to eliminate competition and shorten the mother’s time to her next estrus cycle, increasing their own chances of fathering future offspring. Male brown bears don’t have it easier.

They suffer injuries or even death when fighting rivals over food, territory or mates, and must constantly adapt as they grow larger, older, and face tougher competition. In this contest, voters may find themselves rooting for an older female raising her cubs against the odds, or an older underdog bear facing off against younger, stronger challengers.

Beyond the fun of this online competition, Fat Bear Week helps raise conservation awareness, support habitat protection, and foster public engagement with wildlife. But the future of bear fattening and hibernation patterns might be shaped by climate change.

Shifts in seasonal timings mean that their key food resources, such as berries and salmon, now overlap, and some bears may switch their diets. This can disrupt ecosystems and potentially lead to nutritional imbalances and behavioral changes.

In Spain’s Cantabrian Mountains, warmer winters have led to brown bears remaining active during the winter, a risky time when food is scarce and cubs are vulnerable.

Conversely, some bears can be displaced to lower-quality areas, causing others that currently eat salmon to enter dens earlier and remain inside longer, missing out on critical feeding opportunities.

Fat Bear Week draws attention to the importance of preserving wild habitats like Katmai National Park. It’s a brilliant model of how storytelling and digital media can inspire public stewardship of nature.

This article is republished from The Conversation under a Creative Commons license. Read the original article.