ANCHORAGE, Alaska -- One human wins the Iditarod Trail Sled Dog Race each year, but it's the smaller, furry athletes that do the heroes' share of the work crossing nearly 1,770 kilometres of merciless terrain to reach the finish line on Alaska's wind-battered coast.

The 2014 race began Sunday and is still in the early stages, with jockeying for the lead remaining fluid until all the mushers begin taking a mandatory, 24-hour layover and two eight-hour rests. Five mushers have scratched, leaving 64 teams in the race.

Late Tuesday morning, Iditarod veteran Sonny Lindner was the first to leave the Nikolai checkpoint, more than 700 miles from the finish line in the old gold rush town of Nome. He left at 11:20 a.m. with all 16 dogs he started with, followed two minutes later by Hugh Neff. Mushers say this year's trail is full of gruelling conditions, including stretches of bare ground.

Throughout the race, mushers will keep a close eye on their teams, dropping dogs that are tired, injured or sick. Here are some other key things to know about the four-legged competitors:

It takes a team

Mushers must have 12 to 16 dogs at the starting line, and most choose to go with the maximum. They must have at least six of those dogs to finish the race. If they can't meet that closing minimum, too bad. Race rules say no new dogs can be added on the trail.

Youth versus wisdom

Most Iditarod dogs range from 2 to 7 years old, but some are still running at age 9, with even older dogs participating over the years. On the other end of the scale are the young bucks, some as young as 1 1/2. With a good mix of ages, mushers get frisky youngsters and seasoned veterans. It's the older dogs that have come to memorize the trail. "Like, once a guy's been in the NBA finals, he knows it," race marshal Mark Nordman said.

Super calorie burners

Oh, to have the metabolism of an Iditarod dog. These are not huge animals, generally ranging from 35 to 55 pounds. Yet each sled dog burns through at least 10,000 calories on the trail, continually snacking besides the three squares a day.

Canine trail mix

The Iditarod diet used to be heavy on meat and fish, with some kibble thrown in. But the past decade has seen a reversal of that, Nordman said. Where it was once a ratio of about 30 per cent commercial dog food and 70 per cent meat and fish, it's now the opposite for many teams, thanks to the development of increasingly high-quality commercial dog food. "It's why the pet industry has enjoyed the race so much, because they learn so much from the dogs that they can pass it on to the general community of pets," Nordman said.

Dog team vitals

Yes, dog deaths still occur in the race, including a dropped dog that died of asphyxiation at a checkpoint last year after it was covered by snow from a severe storm. But dog deaths -- slammed by animal rights activists over the years -- have dramatically declined. Last year's death was the first since 2009. Dog care is a huge focus, with an average of six veterinarians assigned to each checkpoint to assess the animals' health through such measures as heart rate, hydration and appetite. Warning signs vets look for include off-kilter gaits and attitudes.