posted March 17, 2013 12:51 AM            

The fatality broke a safety streak that race supporters had cited as evidence of good care for the animals at the center of the contest.

The dog, a 5-year-old male named Dorado in the team of musher Paige Drobny, was found dead on Friday at Unalakleet, an Inupiat Eskimo village and race checkpoint on the Bering Sea coast.

A necropsy, which is the animal equivalent of an autopsy, determined the cause of death was asphyxiation from being buried in snow in severe wind conditions, race marshal Mark Nordman said.

Iditarod mushers begin the race with up to 16 dogs, but they typically leave some at checkpoints as their animals tire. Most mushers finish with a team of about 10 dogs.

Dorado had been left at Unalakleet and was among a group of dogs set to be flown back to Anchorage, Nordman said. The animals were left outside, with their condition checked at 3 a.m. on Friday, he said.

"Between that time and daylight, drifting snow covered several dogs and Dorado was found to be deceased," Nordman said.

Dorado had been dropped off at Unalakleet because of sore muscles, said Iditarod spokeswoman Erin McLarnon.

Most dogs in the Iditarod are huskies or husky mixes.

Animal rights activists have criticized the Iditarod, saying competitors push the dogs too hard in racing and training and subject the animals to dangerous conditions.

"Our stance on the Iditarod has always been that people who care about dogs should not support the race. It's a cruel spectacle," said Ashley Byrne, campaign specialist for People for the Ethical Treatment of Animals.

Iditarod mushers and officials have long defended the race's dog-care record, citing the army of volunteer veterinarians involved each year and the extensive dog health screening conducted before each race.

Sixty-six mushers and their dog teams began the 1,000-mile (1,600-kilometer) Iditarod Trail Sled Dog Race on March 2 in Anchorage. Mitch Seavey won the competition on Tuesday.

Drobny, the competitor whose dog died, reached the Nome finish line on Thursday, in 34th place.

This year's race was marred early on by tragedy. Three people, including a 10-year-old girl, were killed in a March 4 plane crash near Rainy Pass, one of the early race checkpoints. They had been headed to the Native village of Takotna, another checkpoint, to work as race volunteers.

(Editing by Alex Dobuzinskis and Xavier Briand)