ANCHORAGE, Alaska (AP) — For the past five years, Alaska’s annual Iditarod sled dog race has gone off mostly free of controversy, as teams of dogs and their mushers braved the elements in the 1,000-mile (1,609-kilometer) test of endurance across the frozen wilderness.

This year the deaths of three dogs during the race — and five more during training — have refocused attention on the darker side of Alaska’s state sport and raised questions about the ethics of asking animals to pull a heavy sled for hundreds of miles in subzero temperatures.

But dog mushing has a long and storied tradition in Alaska that harkens back to its Native peoples and frontier spirit, and while there are calls to end the race forever, supporters say the Iditarod should remain as a celebration and reminder of a time not so long ago when the main way to travel was by sled.

Archeological evidence suggests dogs were used to pull sleds long before Alaska Natives had contact with other cultures, and they used them to move their supplies as they migrated with the seasons to the best fishing, hunting or trapping spots, said Bill Schneider, the former president of the Alaska Historical Society, retired archivist for the University of Alaska Fairbanks and a recreational musher at age 78.

Dog sleds were quickly adopted as the most efficient way of travel by non-Alaska Natives as well, and one dog was even hailed as a national hero in 1925 for leading a team that delivered life-saving serum to Nome when its population faced a deadly diphtheria epidemic.

Snowmobiles eventually eclipsed mushing, and in the early 1970s the Iditarod was established with the help of Joe Redington Sr., who saw it as a way to save sled dog culture and preserve the Alaskan husky breed. Since then, sled teams — many with 16 dogs in harness — make the arduous journey each March from the city of Anchorage to Nome, on the state’s far west coast.

The three dogs that collapsed and died during the race this year belonged to different teams. One perished just 200 feet (60 meters) from entering a village. Life-saving efforts failed in all three cases, and necropsies have not provided causes of deaths. More tests will be conducted, officials said.

All three mushers withdrew from the competition, pursuant to race rules. They were fairly inexperienced, with two rookies and one in his second race.

Scott Janssen, an Anchorage funeral home director who was known as the “Mushing Mortician” until he retired in 2018, does not blame the mushers for the dog deaths. Janssen made international news in the 2012 Iditarod when he saved his dog Marshall with mouth-to-snout resuscitation.

“You know, every one of these mushers, I can feel their pain as far as having the death occur,” said Janssen, who urged critics to wait for full necropsy reports before passing judgement on the mushers.

People for the Ethical Treatment of Animals and another animal rights group, Humane Mushing, say more than 100 dogs have died over the 51-year history of the Iditarod, which has always declined to provide a number.

Melanie Johnson, a PETA senior manager, said the deaths show that mushers must stop putting their dogs in danger and the race needs to end.

“These are not super dogs; they’re not indestructible pieces of sporting equipment,” she said. “But the Iditarod continues to push them beyond their capabilities, and as a result, dogs continue to suffer and die.”

Iditarod officials did not respond to several messages from The Associated Press seeking comment.

CEO Rob Urbach has rejected PETA’s stance on the race in the past as “inflammatory and grossly inaccurate,” while acknowledging that the criticism creates a difficult dynamic. Iditarod organizers are trying to change the narrative, he said, and continue to promote dog wellness, nutrition, training and breeding.

Janssen said he doesn’t want to see the Iditarod go away because of criticism from animal rights groups. The Iditarod leadership has lost control of the narrative by publicly ignoring the claims of groups like PETA instead of countering them, he added.

“Just like in any business, transparency has to be No. 1,” Janssen said.

After the winner came in Tuesday in Nome, Urbach told the Anchorage Daily News that the dog fatalities were “obviously very disheartening for our community.” Officials are waiting on full necropsy reports and will act based upon the results, he added.

“If we can learn anything, we will,” he said. “When we get all the reports back, we’ll see if there’s anything. I can assure you if we do, we’ll apply those learnings.”

Dallas Seavey, who this week became the first six-time Iditarod winner, had two of his dogs killed and seven injured last November, when they were hit by a snowmobile. He was not driving at the time. For the race, he used some dogs from the kennel of his father, Mitch Seavey, to fill out what became the winning team.

“This was a really tough year, and these guys, they brought it home for us,” an emotional Seavey said at the finish line, after hugging each of his dogs.

When racing, Seavey said, he is “going to take care of these dogs the best we can every single day, get them down the trail as quickly as they can in a healthy, fun manner. And that’s what wins races.”

From its Alaska Native beginnings, mushing evolved in the early 1800s when Russian settlers used dog teams for travel and to move supplies between trading posts. Miners later used teams to haul supplies and even gold during the Gold Rush of the early 1900s. U.S. Army personnel had dog teams on Alaska’s first military bases, and telegraph line repair workers used sleds to reach broken lines.

Sled dog teams also played an important role in connecting Alaska to the outside world. Chester Noongwook of Savoonga was the last carrier to retire his team in 1963, when air service was established to St. Lawrence Island in the Bering Sea, according to the Alaska Geographic Society.

In 1925, the Siberian husky Balto became a national hero for leading his team through blizzard conditions to deliver the diptheria medicine to Nome, just south of the Arctic Circle, and was honored along with his musher with a bronze statue in New York’s Central Park.

Schneider, the historian, said dogs were chosen for the trip of about 670 miles (1,085 kilometers) because they were deemed safer than planes, which were still in their infancy.

Airplanes “could have gotten the serum there easier, but it was not as reliable,” Schneider said. “It’s become an important story in the dog mushing world.”