This episode was written by Lindsey Taylor, whose blog “The Curiosity Chronicles” follows her adventures around the world.

Every fall in one of the largest national parks in America, visitation slows to a near halt by the end of September. The ground is already covered with golden aspen leaves and the mountaintops are powdered with snow called “termination dust”. The skies lose up to 9 minutes of sunlight every day and the northern lights dance over the crisp landscape at night. While so much of the park and landscape slows into the winter, there is one group of individuals that eagerly await the snow.

On this episode of America’s National Parks: the sled dogs of Denali National Park.

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These official park employees—or as some call them, canine rangers—have an important role to play year-round. As the only kennel in the National Park System, the Denali Park Kennels already receive welcome attention from visitors, most of them traveling during the summer. But as the buses stop arriving with travelers in the fall, the dogs prepare for their true purpose in the park. Each winter, they will cumulatively run more than 1,500 miles as a team. They will haul scientific supplies or construction equipment into the far reaches of the wilderness, or bring construction debris back to the entrance of the park. Through blowing snow, below-freezing temperatures, or bright sunny skies, the dogs will lead the way.

Denali has had sled dogs woven into its history since its establishment. Harry Karstens traveled to the Yukon from Chicago during the Klondike gold rush of 1897. He was just 19 years old. Though he searched for gold along the Seventymile River, like many prospectors, he didn’t find much. But other reasons to stay in Alaska kept finding him.

Karstens built a telegraph line that linked distant Alaskan outposts and hauled supplies for the U.S. Army. He also gained a remarkable reputation as a dog musher, where he hauled mail across the landscape, helping create the route from Valdez to Fairbanks. When he transported mail, he had a handful of dogs attached to his sled, much unlike the twelve-dog teams we see in races today. The sled weighed hundreds of pounds, and there was no room on the back for a grown man. Instead, Harry Karstens was frequently breaking trail in front of his dogs, walking and running through deep snow and winter temperatures reaching 50 or 60 below.

When the naturalist Charles Sheldon set off in what is now Denali National Park and Preserve in 1907, ten years before the park’s creation, he hired Harry Karstens and his team of sled dogs to help him with his winter wildlife studies. His dogs would also prove invaluable during the Karstens-Stuck expedition in 1913, pulling supplies to the head of the Muldrow Glacier at 11,500 feet, leading Karstens, Hudson Stuck, and Walter Harper—a nineteen-year-old Alaska Native—to successfully summit Denali.

In 1921, Harry Karstens became the first park ranger for the then-named Mt. McKinley National Park. His first and most pressing task was to control illegal poaching. Miners and settlers were hunting caribou, moose, and Dall sheep to feed their camps. Harry Karstens founded the park kennels to provide a reliable and efficient source of transportation through the wintry landscape. As the years went on, sled dogs helped rangers record wildlife populations and patrol the park’s boundaries. The park hired more rangers so that they could each explore a different district with a team of seven dogs. The rangers even built cabins along the park boundaries for patrols, which could last months at a time. Many of the cabins are still in use and continue to break up long winter travel for the Denali sled dog teams.

In 1929, the park service built a kennel building near the dog yard that still stands today. Within seven years, the park was caring for more than 60 adult dogs and pups at the kennels, and more and more tourists were visiting them when they traveled to the park.

Sled dogs have even been known to save human lives. A Denali park ranger named John Rumohr was patrolling in January 1940 when his sled broke through the ice of the wide Toklat River. He shared his experience with the Fairbanks newspaper:

“I was in serious trouble. Breaking through the ice over a deep channel, where I could reach no bottom by sounding with my eight-foot geepole, the dogs had to swim to get the sled out. What really saved my life was Tige.

The dog had been sick and I was not using him in the team, but let him follow behind. While I was working with the sled he managed to get up ahead of the team and really coaxed them along . . . . It was quite a struggle for we had about 100 feet to go before we reached solid ice. The dogs would never have made it if Tige had not been ahead of them. Whenever he came to a place where the ice would carry him he would turn to the team, cry a little and wag his tail. That would put new spirit in them and they would struggle ahead even if the ice broke under them.

I hope Tige will get a long life. He earned it that day.”

In the 1940s, many of the sled dogs were given to the military during World War II. In Fairbanks, up to 200 sled dogs were maintained by the U.S. Army 10th Air Rescue Squadron into the early 50s. The dogs performed rescue missions in teams of ten and had to be on alert 24 hours a day. But one Army caretaker claims the dogs were fed exceptionally well, as the government purchased red meat, dry and canned commercial dog food, and locally dried salmon “by the ton”. The rest of the sled dogs in Mt. McKinley National Park were retired, as some believed machines to be more efficient for winter travel. John Ruhmohr had opinions on this idea, too.

“The distance traveled in a day over unbroken trail exceeds the best a dogteam could perform. But . . . dogs have less trouble with their carburetors. You can cuss the Snow Tractor and it just sits there. When you cussed your dogs, they would at least raise their ears.”

Rumohr later helped acquire dog teams for the park again in 1950. They were used for some patrols as well as visitor programs. Years later, two major federal laws reinforced the National Park Service’s commitment to keeping dog teams in the park. In 1966, the National Historic Preservation Act declared that “the historical and cultural foundations of the Nation should be preserved as a living part of our community life and development in order to give a sense of orientation to the American people.” Sled dogs are adaptable and reliable in the unpredictable landscape of the park, and they are a part of Alaskan culture.

The modern sled dog program in Denali was brought back in 1974 by Sandy Kogl, the first full-time kennel manager, who exercised, trained, bred, and cared for the sled dogs. She also taught other rangers to drive dog teams, managed the backcountry ranger program, and mentored seasonal rangers. Sandy helped the park return to its traditional use of dog teams in the backcountry by improving the breeding program, renovating facilities, and initiating more backcountry dog sled patrols.

The second law that provided more incentive to continue sled dog use in the park was the Alaska National Interest Lands Conservation Act, also known as ANILCA (ah-NIL-ka), which was passed in 1980. In this act, the name of the park was changed from Mt. McKinley to Denali National Park and Preserve, the park tripled in size, and the original 2 million-acres from Mt. McKinley National Park were designated as a federal wilderness. Mechanized equipment and motorized vehicles are prohibited in wilderness areas, but the Denali sled dogs allowed rangers to continue using winter patrols to carry out the park’s mission.

Henry P. Karstens Collection, 0630, Karstens Library

Today, sled dogs still have an active role in Denali National Park. They help freight supplies throughout the park, which means they are bred to be larger and stronger than dogs you would see in the famous Iditarod sled dog race. Sound researchers pass off their monitoring equipment to mushers and dogs in the fall, who will transport the gear to various backcountry locations. The dogs also transport construction equipment to restore historical cabins, conduct ground-based censuses of golden eagles at their nesting locations and collect snow sampling data. In November and December, temperatures can drop as low as 40 below and daylight only lasts 4 hours. Some patrols into the park take weeks and some last only one day.

The sled dogs that you’ll find in Denali National Park may look different than you’d expect. Called Alaskan Huskies, they are more of a type of dog than a breed. Mushers in Alaska bred dogs from Inuit villages with other breeds such as Siberian Huskies, Greyhounds, and German Shorthaired Pointers. Dogs were bred based on the qualities needed by the musher, whether they needed speed, strength, a certain type of coat, or stamina. Because they are a mix of many different dogs, all Alaskan Huskies can look very different. They can be different sizes, shapes, and have different colors and fur patterns.

So what does the everyday life of these National Park Service ranger pups look like?

Most puppies are born at the kennels in the park. For two months, the puppies sleep, nurse on milk, and gain a pound or more per week. There is never enough love for them while they grow, as children and adults hold and snuggle them often. When the puppies are grown, they will be surrounded by many visitors in the summer season, so this socialization, when they are young, is incredibly important.

Socialization with adult dogs is important, too. In the early winter season, adults begin training runs and the pups—now around 6 months old—will join the adults on training runs, often running beside the team while they scramble over glare ice and push through blowing snow. They learn about the natural winter conditions in Denali and observe the adult dogs harnessed as a team.

The seven-month-old pups will finally get their chance to be harnessed with the team, strategically placed next to the well-trained adults. It’s not unusual for them to try to play mid-run, get distracted, and chew on the lines. They are puppies, after all! Though training will continue throughout their lives, sled dog pups will have achieved hundreds of miles of experience running in harnesses after their first winter.

In Denali, sled dogs retire around 9 years of age. By that time, many dogs have completed more than 8,000 miles of winter travel. The sled dogs are adopted by families that live locally or in northern locales and can provide them with active, outdoorsy lifestyles in retirement. Though nine years may seem like an old dog, Denali’s canine rangers have unmatched energy at that age and need to keep up an active lifestyle to stay happy and healthy.

Humans have had a close relationship with dogs for millennia. In archaeological digs in Siberia that date back 8,000 years, dogs have been found buried alongside people or with jewelry. It is not known exactly when dogs were first pulling sleds. In Alaska, some evidence suggests that coastal Alaska Native populations may have harnessed dogs for pulling sleds around 500 to 1,500 years ago. Alfred H. Brooks, the head of the U.S. Geological Survey, wrote in the early 1900s: “Countless generations of Alaskan natives have used the dog for transport, and he is to Alaska what the yak is to India or the llama to Peru.”

In the mid-to-late 1800s, hunters and explorers of European descent began to settle in what is now Alaska. They learned from natives that sled dogs were the most reliable transport in the frozen, unpredictable landscape, and the dogs soon became the primary mode of transportation between outposts for both goods and passengers. The discovery of gold in the Yukon River drainage in the 1890s brought a larger network of winter trails and trading sites and also meant that sled dogs were in high demand. Miners brought any dog that could pull a sled into the land, such as retrievers, hounds, Saint Bernards, and Newfoundlands.

In modern kennels, at first glance, the set-up may seem peculiar. Dogs are usually tethered to their own individual houses to give them their own private space whenever they need it. The tether is long enough for the dogs to interact and play with other dogs in the yard, but not so long that there is a hazard for their safety. The dog houses are made out of thick logs with a flat roof and a small entrance door so that dogs can be sheltered from the elements. Though whatever the season, the roof on top of the house is where the dogs prefer to be, watching birds and their neighbors.

In the summer, the Denali sled dogs take part in the sled dog demonstration, a 30-minute interpretive ranger program that happens three times a day in peak season. This is the most popular interpretive ranger program in the park with more than 50,000 people attending annually. The Denali Park Kennels also rely on an incredible volunteer support system to give dogs the extra exercise and attention they need in the summer. Locals living in the area can “adopt” a sled dog and walk them for at least an hour, three times per week. Each sled dog will have more than one walker to ensure they stay active every day. More than 50 volunteers cumulatively donate thousands of hours walking and snuggling the canine rangers each summer.

If you’re looking to visit the Denali Park Kennels in summer, you’ll find the kennels at Park Headquarters, or about 3 miles down the park road from the entrance. Sled dog demonstrations are offered three times a day between June 1st and September 1st. Visitors traveling outside of those dates can head to the Denali Visitor Center for demonstration times.

In winter, inquire at the seasonal visitor center if the dogs are around at the kennels. Rangers and dogs are often traveling deep in the park’s wilderness for days or even weeks at a time.

Whenever you find time to visit the kennels, keep these tips in mind. Let the dogs come to you, and let them sniff you before you pet them. If you see dogs that are barking, yawning, or panting, it means they’re nervous and you should move away to give them space. Always supervise children while interacting with dogs and don’t run or make fast movements around them, as it can startle them.

Every new litter of pups in Denali grows up with the same energy and passion to run as generations of Alaskan huskies before them. From traditional use in Alaska Native cultures to the team that assisted the first recorded summit of Denali, the sled dogs are an iconic symbol of Denali’s wilderness. In the late summer evenings, if you’re lucky enough to hear the dogs howling to mountains painted in alpenglow, you will feel in your heart how they have shaped the history of the park forever.