Like many top athletes, Sultana trains hard and has no time for the shenanigans of younger teammates. But you won’t find her in a stadium. Sultana is a sled dog born and bred to work in the punishing winters of Alaska’s Denali National Park and Preserve, and she’s gearing up for another season on the trail.

Right now, sled dogs around the world are busy preparing for the upcoming racing season or for jobs hauling equipment or tourists. Premier events like the Iditarod, the Yukon Quest, or the International Pedigree Stage Stop kick off over the next couple of months, drawing as many as 1,300 dogs and thousands of people to frozen places from Alpine, Wyoming, to Nome, Alaska.

Like Sultana—a trailbreaker who moves supplies for researchers and park staff—the animals competing in these races are a cut above your normal dog.

Contrary to popular belief, Siberian huskies or Alaskan malamutes are not the most popular sled dog breed. That spot belongs to the Alaskan husky, an unofficial breed with a hodge-podge heritage that’s custom-made for the rigors of racing and hauling.

View Images Eight-year-old Sultana is one of the best lead dogs at the Denali National Park kennels. PHOTOGRAPH BY DANIEL A. LEIFHEIT, NPS

Don’t let their scrappy looks fool you. Generations of breeding have produced animals that love to run, are capable of pulling hundreds of pounds through the snow, and that work together like a well-oiled machine.

The Crucial Ingredients

To breeders, sled dogs’ looks don’t matter as much as performance does. No matter the breed or whether they’re racers or freight-haulers, all these dogs have an insatiable need to go. Howard Thompson, a former racer who now breeds sled dogs near Mondovi, Wisconsin, calls it wanderlust. It’s the idea that “somewhere else is better,” he explains.

A healthy appetite is essential, Thompson adds. Long-distance sled dogs—those competing in events over 300 miles (483 kilometers) long—or freight-haulers like Sultana are out for days or weeks at a time. They can’t be finicky about their meals or prone to digestive issues, he says.

Sled dogs also need tough feet, says Charlotte Mooney, a racer and breeder in West Yellowstone, Montana. Racers can use booties to protect a dog’s paws, but the footwear slows the animals down, she says. Not ideal for sprint races—events less than 30 miles (48 kilometers) long—where dogs run full blast for the duration.

Leaders, Swing Dogs, and Wheel Dogs

View Images EMILY M. ENG, NG STAFF. SOURCES: JENNIFER RAFFAELI; HOWARD THOMPSON

Teamwork is also key. Attach a pack of “normal” dogs to a sled, and they’re not likely to go far before chaos ensues.

Lead dogs—the ones out in front—help maintain order. They execute a musher’s commands, set the team’s pace, and ensure everyone’s going in the right direction.

A good lead dog can also think for itself, says Jennifer Raffaeli, manager of Denali’s kennels. They must have the confidence to disobey if a musher’s commands will send them over bad ice or off a cliff. And it helps if they can keep the others in line. Sultana is part of the Denali kennel, and she’s one of Raffaeli’s best leaders.

She’s tough enough to keep the young males focused on work, Raffaeli says, and smart enough to take advantage of inexperienced drivers, or mushers.

When the blue-eyed, eight-year-old Alaskan husky wants a break, she’s been known to stop on a trail, turn around, and come back to the driver while dragging the rest of the team behind her. When Sultana is with an experienced driver, though, she’ll do whatever is asked of her, the kennel manager says.

Backing up lead dogs like Sultana are the swing dogs—positioned right behind the leaders. They help to turn the team left or right. Wheel dogs may be last in line, but they help to steer the sled. The good ones know to go wide on turns to guide the sled around trees and other obstacles, says Thompson.

The dogs in between the swing and wheel positions are called team dogs; they provide the muscle. Their job is to keep pulling until it’s time to stop.

“A Strong Dash of Greyhound”

That willingness to work is a hallmark of sled dogs. But Raffaeli, who breeds all the dogs the park uses, also looks for a sociable personality. The animals interact with visiting tourists during the summer months, so aggressive dogs just won’t do. (Watch how the park raises its puppies.)

View Images Spur, Sultana’s brother, is a reliable leader who’s a pro at spotting bad ice. PHOTOGRAPH BY DANIEL A. LEIFHEIT, NPS

A tendency toward aggression is likely one reason why Alaskan malamutes—historically used as sled dogs—have fallen out of favor with many racers, says Thompson, who used to use them. “They have a bad reputation in the sled dog community.”

They’re also slow. “If you want to come in last, race malamutes,” he says.

Siberian huskies, another iconic sledding breed, have also been overtaken. The Alaskan husky, which owes a good portion of its heritage to Siberian huskies and malamutes, are now the “premier” sled dog breed, Thompson explains.

The American Kennel Club doesn’t officially recognize the group, but Alaskan huskies are genetically distinct from purebreds, research has shown.

Breeders looking to boost speed mixed Alaskan huskies with German or English pointers, says Thompson, and added “a strong dash of greyhound.”

View Images Denali’s sled dogs shift gears during the summer months, giving demonstrations and interacting with visiting tourists. PHOTOGRAPH BY NEIL BLAKE, NPS

The “marathon” runners—including dogs running in the Iditarod—have some border collie, hound, or pointer mixed in, says Stuart Nelson, Jr., head veterinarian for the Iditarod.

No matter the breed, though, most sled dogs seem happiest when out on the trail. And somehow, they’re able to communicate that love to the people they meet, says Raffaeli. “These dogs, even though they don’t speak, manage to communicate to our visitors about the importance of wild spaces.”