Stamina and Strength

Many breeds of dogs are used to pull sleds, including official American Kennel Club breeds such as the Siberian husky, malamute and Samoyed. However, many sled dogs are of mixed breed and are called Alaska husky or Eskimo dogs. While some sled dogs may have wolf bloodlines, it's generally not desirable to crossbreed sled dogs with wolves.

Fon, an Alaskan husky sled dog
Jim Watson/AFP/Getty Images
Mushers look for easygoing dogs that are mentally tough and up to the challenge of pulling a racing sled.

Sled dogs are bred for their speed and endurance as well as leadership qualities. They are big dogs with thick coats and wide, flat feet. They sleep with their tails covering their noses to keep warm. Dogs that weigh around 40 to 45 pounds (18 to 20 kg) are the ideal size to pull sleds, but some may weigh as much as 85 pounds (38.5 kg).

Young dogs that are enthusiastic runners, easygoing and mentally tough are good choices for sled dogs. A dog's gender matters little -- both male and female dogs are considered equally.

For racing, the most intelligent and fastest dogs are picked to be lead dogs and run in the front of the pack. Behind them run swing dogs, whose job is to direct the team around turns and curves. At the back of the dog team are the wheel dogs or wheelers, who are right in front of the sled and are usually the largest and strongest of the team. The rest of the dogs are known simply as team dogs.

Hazards for Sled Dogs
 Despite their physical capabilities and even temperaments, sled dogs face danger when they pull a sled. They often cross snowy, icy, uneven terrain, running at fast speeds. Their feet can get hurt, they can get dehydrated and they can fall through ice. Some dogs simply die from overexertion. Attacks by animals, including moose and wolves, sometimes occur. While not frequent, another dog on the team could start a dog fight. Other dangers include getting tangled in the lines, or breaking free and getting lost.

­Dogs are typically from 2 to 10 years old when they pull sleds. After they retire, they might remain with their owner at a kennel or be adopted as pets by others. Rescue groups for sled dogs take in unwanted dogs and care for them, trying to place them in loving homes.

While snowmobiles (also called snow machines), helicopters and airplanes are now often used in place of sled dogs, there are still times when canine transportation is preferred. Harsh weather conditions can make flying hazardous, and certain terrain can be more difficult for snow machines to cross than for dogs. Dogs can be more reliable than man-made machines, they're good companions to have on long treks and they can be cheaper to own than other forms of transportation.

­Famous Sled Dogs (Real and Fictional)
 ­­Baldy of Nome - Musher Scotty Allan's dog who helped him win multiple All-Alaska Sweepstakes in the early 1900s and was featured in Esther Birdsall Darling's book "Baldy of Nome."

Balto - The lead dog in the final segment of the 1925 Alaskan serum run from Nenana to Nome (the Iditarod race commemorates the run), who is immortalized with a statue in New York City's Central Park.

Buck - Fictional star of Jack London's "Call of the Wild."

Taro and Jiro - Survivors of a 1958 Japanese expedition to Antarctica, the dogs' story was told in the movies "Nankyoku Monogatari" and "Eight Below."

Togo­ - The lead dog for the longest leg of the 1925 Alaskan serum run from Nenana to Nome, an accomplishment some feel was overshadowed by Balto's fame.

Navarre of the North - grandson of Baldy of Nome and featured in Esther Birdsall Darling's book "Navarre of the North."

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In the next section, we'll find out how a dog becomes a sled dog and if most mushers treat their pack humanely.