Alaska’s annual Fat Bear Week contest got off to a delayed start because a female participant known as Bear 402, was killed by a male during a livestreamed fight.

Cameras set up in the park to capture footage of the bears recorded the killing on Monday.

The contest, which is in its tenth year, celebrates the resiliency of the 2,200 brown bears that live in the preserve on the Alaska Peninsula. It allows the public to vote for its favourite “fat bears” from a shortlist.

“National parks like Katmai protect not only the wonders of nature, but also the harsh realities,” Matt Johnson, park spokesman said in a statement. “Each bear seen on the webcams is competing with others to survive.”

The nonprofit http://explore.org, which streams the uncensored bear footage and helps organise Fat Bear Week, hosted a live conversation about the death on Monday. Sarah Bruce, a Katmai National Park ranger, said it was not known why the bears started fighting.

“We love to celebrate the success of bears with full stomachs and ample body fat, but the ferocity of bears is real,” said Mike Fitz, explore.org’s resident naturalist. “The risks that they face are real. Their lives can be hard, and their deaths can be painful.”

The contest this year features 12 bears that have been packing on the pounds all summer.

Adult male brown bears typically weigh 600 to 900lbs in mid-summer. By the time they are ready to hibernate after feasting on migrating and spawning salmon — each eats as many as 30 fish per day — large males can weigh well over 1,000lbs. Females are about one-third smaller.

Bear 909 Jr, who last week won the Fat Bear Junior competition for the second time, will be up for a public vote against Bear 519, a young female, in the first round. The winner will face the defending champion, Grazer, described as one of the most formidable bears on the river.

Another first-round match in the popularity contest pits Bear 903, an 8-year-old male who was given the nickname Gully after he developed a taste for seagulls, against Bear 909, the mother of Bear 909 Jr. The winner faces a two-time champion, a bear so large it was given the number of the equally massive aeroplane, Bear 747.

In the other half of the bracket, the first-round match has Bear 856, an older male and one of the most recognisable bears on the river because of his large body, challenging a newcomer, Bear 504, a mother bear raising her second known litter. The winner will face perhaps the largest bear on the river, 32 Chunk, a 20-year-old male who once devoured 42 salmon in 10 hours. It is estimated to weigh more than 1,200lbs.

The last first-round match has Bear 151, a once-playful young bear nicknamed Walker now showing more dominance, versus Bear 901, a solo female who has returned to the river after its first litter did not survive. The winner will face Bear 164, called Bucky Dent because of an indentation in his forehead.

Voting in this year’s tournament-style bracket is open through Oct 8.

More than 1.3 million votes were cast last year.