Fat Bear Week: the great Alaskan bear-belly contest that turns survival into a global spectacle

Imagine a beauty contest in which the contestants are judged not for their elegance, athleticism, or good looks, but for the size of their bellies.
The bigger, rounder, and more spectacularly chubby, the better. It might sound like a joke, but in the wild landscapes of Alaska, this is a very serious annual event, where being fat is not a fashion statement but a matter of life and death.
Gaining weight is not only encouraged but celebrated, where a growing belly is a sign of success and the biggest contestant takes home the ultimate prize. No gym memberships, no personal trainers, no calorie counting.
In fact, the only thing that matters is eating as much as possible before winter arrives!

It might sound like the strangest sporting event imaginable, but every autumn this is precisely what happens in southwestern Alaska.
Welcome to Fat Bear Week, the annual competition that turns the brown bears of Katmai National Park and Preserve into international celebrities. Their mission? To become as impressively round as possible before retreating into their winter dens. The judges? Thousands, sometimes millions, of people watching from their computers and phones.
And the prize? Eternal internet glory.
The stars of this unusual event gather around Brooks River, a waterway that becomes one of the greatest natural fishing grounds in North America during the summer salmon migration. Here, the bears spend weeks doing what they do best: fishing, eating, sleeping, and repeating the process with remarkable dedication.
The setting is spectacular.
Katmai is a vast wilderness of mountains, forests, lakes, rivers, and volcanic landscapes, home to one of the largest concentrations of brown bears in the world. It is also a place where nature still operates on an extraordinary scale. In some areas, bears outnumber people, and the annual return of the salmon provides an abundance of food that would be difficult to imagine anywhere else.
The bears seen at Brooks River are often called coastal brown bears, and belong to the same species as grizzly bears, Ursus arctos, but coastal populations generally grow considerably larger thanks to their access to exceptionally rich food sources, particularly salmon.
In fact, the availability of this protein- and fat-rich fish helps explain why some Katmai males become such enormous animals.

Their annual feast begins with one of nature’s most remarkable journeys: the migration of Pacific salmon.
After spending years in the ocean, sockeye salmon return to freshwater rivers to reproduce, often travelling hundreds of kilometres upstream to reach the streams where they were born. Their extraordinary sense of navigation helps them locate these ancestral waters, guided in part by chemical signals associated with their original freshwater environment. Along the way, they must overcome powerful currents, natural obstacles, predators, and exhaustion.
At Brooks Falls, the journey becomes particularly challenging.
The waterfall creates a natural barrier, forcing the salmon to leap out of the water in an attempt to reach the upper river. For the bears waiting nearby, this is essentially an all-you-can-eat buffet with very little table service required.
Some bears stand directly in the rushing water, using their paws and jaws to snatch fish as they leap. Others wait patiently at the top of the falls, positioning themselves where salmon are most likely to land. The more experienced individuals develop remarkably efficient techniques, catching fish with astonishing precision.
And then there are the bears that seem to have mastered the art of doing absolutely nothing while still getting dinner.
Rather than chasing fish, they simply sit in the river and wait for salmon to swim within reach. It is a remarkably energy-efficient strategy, particularly when the river is full of food.

One of the most famous practitioners of this approach was bear 480, better known as Otis. A true celebrity among wildlife webcam enthusiasts, Otis became famous for his relaxed fishing style, often sitting almost motionless in the water while waiting for the perfect opportunity. His patience earned him the affectionate nickname “the Zen Master.” Even as an older bear with missing teeth, he continued to fish successfully, proving that experience can sometimes be more valuable than speed.
Otis also became one of the most successful contestants in Fat Bear Week history, winning the competition four times: in 2014, 2016, 2017, and 2021. His popularity was so great that viewers followed his appearances with the enthusiasm usually reserved for sporting heroes.

But he is not the only celebrity in Katmai’s bear community.
Bear 747, whose enormous size has made him one of the most impressive animals ever observed at Brooks River, has also earned legendary status. His name is particularly appropriate: some estimates have placed his autumn weight at around 1,400 pounds (635 kilograms), making him one of the largest bears known to frequent the river.

Another familiar face is 128 Grazer, a powerful female known for her distinctive light-coloured ears and fiercely protective attitude towards her cubs. She has repeatedly demonstrated that female bears can be formidable competitors, particularly when defending prime fishing locations. Her achievements are even more remarkable considering that raising cubs requires enormous energy and dedication.
In 2023 and 2024, Grazer won Fat Bear Week, becoming the first female bear to claim consecutive titles. Her success also highlighted an important aspect of the competition: the biggest bear is not necessarily the only impressive one. Survival, maternal care, resilience, and the ability to navigate the complex social world of Brooks River all contribute to a bear’s story.

Another remarkable contestant is 32 Chunk, a huge male whose impressive proportions have made him a fan favourite. He eventually claimed the 2025 championship after several years of finishing among the finalists. Even a serious injury to his jaw did not prevent him from becoming one of the most successful bears in the competition. His victory demonstrated just how much individual determination and adaptability can matter in the wild.

Of course, all this extraordinary eating has a very important purpose.
For bears, autumn is not simply a season of abundance; it is a race against the clock.
As winter approaches, food becomes increasingly difficult to find.
The salmon disappear after spawning, vegetation becomes scarce, and temperatures drop dramatically. The bears must therefore accumulate enough energy to survive several months without feeding.
This period of intense eating is known as hyperphagia, a physiological state during which bears consume enormous quantities of food and rapidly build up fat reserves. Their appetite increases dramatically, and the hormonal mechanisms that normally signal fullness are altered. One important hormone involved in regulating appetite is leptin, whose signalling is suppressed during this seasonal feeding period.
The results are astonishing.
Some bears can gain several pounds in a single day, and large adult males may consume dozens of salmon within 24 hours. According to the US Department of the Interior, a sockeye salmon can provide approximately 4,000 calories. One particularly hungry bear was observed eating around 40 salmon in a single sitting, representing a potential food intake of roughly 160,000 calories!
That is an extraordinary amount of energy, even by the standards of the animal kingdom.

But there is another curious detail about their eating habits: when salmon are particularly abundant, bears sometimes practise a feeding strategy called high-grading. Instead of eating the entire fish, they selectively consume the most energy-rich parts, such as the skin, brain, and eggs, leaving behind much of the less fatty flesh.
To a human observer, this might look like an incredibly wasteful meal. For a bear trying to accumulate as much fat as possible in a limited period, however, it makes perfect sense. Why spend energy digesting less nutritious food when the best calories are already available?
The salmon feast also benefits far more than the bears themselves.
These fish carry nutrients accumulated in the Pacific Ocean into freshwater ecosystems, where their bodies eventually provide food for eagles, gulls, foxes, insects, and countless other organisms. Bears sometimes carry their catches away from the river, leaving partially eaten fish along the banks and in surrounding vegetation. In this way, marine nutrients are transported into the forest, helping to support an entire network of terrestrial life.
It is a remarkable ecological partnership: salmon bring nutrients inland, bears distribute them, and the wider ecosystem benefits.
Meanwhile, the bears continue to grow.
As their bodies accumulate fat, their appearance changes dramatically. Their necks seem to disappear, their shoulders become enormous, and their bellies develop a distinctive rounded shape. Some individuals become so bulky that it is difficult to believe they are the same animals seen in early summer.

And this is precisely what inspired Fat Bear Week.
The competition began in 2014, when Katmai park ranger Mike Fitz noticed a series of photographs posted by a fan of the park’s live webcams. The pictures showed the same bear in June and September, and the difference was so astonishing that Fitz and his colleagues decided to turn the transformation into a public contest.
The first event was called Fat Bear Tuesday and took place on September 30, 2014. Viewers voted using Facebook likes, choosing between photographs of bears at different stages of the summer feeding season. The idea was an immediate success, and the following year the competition was expanded into a full week.
Since then, Fat Bear Week has become an international phenomenon, attracting enormous audiences from around the world. The format resembles a knockout sporting tournament: bears are matched against one another, and viewers vote for their favourite until only one remains.
Interestingly, there are no strict scientific judging criteria. Participants can consider overall size, apparent weight gain, the difference between spring and autumn photographs, or simply the personal story of a particular bear. It is as much a celebration of individual animals as it is a competition.
There is even a separate event called Fat Bear Junior, dedicated to younger bears.
After all, growing up in Katmai also requires a considerable appetite, and the younger generation deserves its own moment in the spotlight.
The webcams are a fundamental part of the experience. Operated through Explore.org in partnership with the National Park Service, they allow viewers to watch the bears in real time, often for hours at a stretch. Cameras positioned around Brooks Falls offer spectacular views of the fishing activity, while other cameras capture different parts of the river and the surrounding habitat.
One particularly fascinating feature is that viewers can begin recognising individual bears.
Their identification numbers, scars, fur colours, habits, and personalities make them surprisingly easy to distinguish once you become familiar with them. Some fans follow particular animals throughout the summer, celebrating their successful fishing days and worrying when a favourite bear disappears from view.
It is not unusual for people to develop genuine emotional attachments to these enormous animals. There are online discussions, fan communities, voting campaigns, and even elaborate arguments about which bear deserves the crown. For a competition based on body fat, the level of devotion is quite extraordinary.

But while viewers are busy comparing bellies, scientists have been trying to answer a rather more complicated question: how much do these bears actually weigh?
For years, the competition relied mainly on photographs and visual estimates. Yet a bear’s apparent size can be deceptive. Its posture, angle, fur, and position in the water can make it look larger or smaller than it really is. And weighing a wild animal that can exceed 600 kilograms is hardly a straightforward operation.
Capturing a bear, sedating it, and transporting it to specialised weighing equipment would be difficult, expensive, and potentially dangerous for both the animal and the people involved.
In 2018, an ingenious idea emerged from an unexpected field: civil engineering.
Joel Cusick, a geographic information specialist working with the National Park Service, wondered whether the terrestrial laser scanners normally used to measure buildings, roads, and construction sites could also be used to measure bears.
The technology is known as LiDAR, short for Light Detection and Ranging. It works by sending out laser pulses that bounce off surrounding surfaces and return to a sensor. By calculating the time taken for the light to travel back, the system can determine distances and construct remarkably detailed three-dimensional models.
The challenge was to scan an animal that was very much alive and had no intention of standing still for scientific purposes.
Fortunately, the bears at Brooks Falls provided an unexpected opportunity. When waiting for salmon to jump, they sometimes remain almost motionless in the water for several seconds. From a nearby observation platform, researchers could scan their bodies without approaching or disturbing them.
The resulting digital models allowed scientists to estimate the bears’ body volume. From there, mathematical calculations could be used to obtain an approximate weight.
The technique was not perfect. Researchers initially had to work with partial scans, estimating the volume of the entire animal from the visible portion of its body. They also needed to account for differences in body composition, since muscle, fat, and water do not all have the same density.
One of the most striking early results involved bear 747, whose estimated autumn weight reached approximately 1,408 pounds (639 kilograms) in 2019. It was a remarkable illustration of just how enormous these animals can become.
The experiments also opened the door to something much more important than a wildlife competition. If scientists could estimate the body mass of bears without capturing them, the same technology might help monitor the health of other difficult-to-study populations.

This is where polar bears enter the story.
Researchers from the US Fish and Wildlife Service, the National Park Service, and the US Geological Survey began exploring whether laser scanning could be adapted to monitor polar bears in the Arctic. Their body condition is an important indicator of health, reproductive success, and their ability to survive in an environment undergoing rapid changes.
In 2022, scientists travelled to the Oregon Zoo to test the technology on two polar bears, Nora and Amelia Gray. Unlike wild bears, these animals were regularly weighed by their keepers, giving researchers reliable measurements against which to compare the laser estimates. The bears were scanned while enjoying frozen treats, and their cooperation helped scientists refine the method.
It was a rather unusual scientific experiment: the same technology inspired by Alaska’s fattest brown bears could potentially help researchers understand how climate change is affecting the health of polar bears thousands of kilometres away.
And the need for such research is increasingly urgent. As Arctic sea ice retreats, polar bears have fewer opportunities to hunt seals, their principal food source. Monitoring changes in their body condition could provide valuable information about the consequences of these environmental changes.
Yet the most important transformation taking place in Katmai is not necessarily visible in the bears’ enormous bellies. It is happening inside their bodies, as they prepare for the long months ahead.
When winter finally arrives, the bears retreat into their dens and enter a prolonged period of dormancy known as torpor. Although commonly described as hibernation, bear torpor is not identical to the deep hibernation experienced by smaller mammals. Their body temperature falls only moderately, but their metabolism slows dramatically. They can remain in their dens for months without eating, drinking, urinating, or defecating, relying almost entirely on their stored fat.
During this time, they can lose up to a third of their body weight. What looks like excessive fat in October becomes an essential energy reserve in January and February.
For pregnant females, this period is particularly remarkable. After mating during the summer, fertilised embryos do not immediately begin developing. Instead, they undergo a process known as delayed implantation, in which the embryo temporarily remains at an early stage of development. Implantation occurs later, when the female enters her winter den, provided she has accumulated sufficient nutritional reserves.
The cubs are usually born in January or February, while their mother is still inside the den. Newborn brown bears are astonishingly small compared with their enormous mothers, weighing only a few hundred grams. They are blind, almost hairless, and completely dependent on their mother’s warmth and exceptionally rich milk.
By the time spring arrives, the family emerges into the outside world, and the mother must begin feeding again while caring for her young. The fat accumulated during the previous autumn has helped sustain not just one animal, but an entire new generation.
This is why Fat Bear Week is about much more than celebrating oversized animals. The bears’ extraordinary weight gain is a visible sign of a healthy ecosystem, one capable of supporting abundant salmon runs and allowing wildlife to thrive.
Of course, nature is never quite as predictable as a competition bracket. Salmon numbers fluctuate from year to year, fishing conditions change, and the bears must constantly negotiate their place within a complex social hierarchy. Dominant males often claim the most productive fishing spots, while younger or less powerful individuals must find alternative locations or wait for an opportunity.
Even so, Brooks River remains one of the most extraordinary places in the world to witness the relationship between a predator and its food source.
And perhaps that is what makes Fat Bear Week so appealing. It takes a fascinating natural phenomenon and turns it into something accessible, entertaining, and unexpectedly moving. Behind every photograph is an individual animal with its own history, challenges, habits, and survival strategies. Behind every round belly is a summer spent fishing, competing, and storing the energy needed to endure another Alaskan winter.

So, when the next autumn arrives and the bears return to their favourite fishing spots, millions of viewers will once again be watching. Some will cheer for Otis’s legendary successors, others will support the enormous 747 or the determined Grazer, and many will simply wait for the moment when a particularly impressive bear waddles into view.
The rules are simple: eat well, get bigger, and survive the winter.
In Katmai, being the fattest bear is not a question of vanity.
It is the ultimate badge of survival.