“Want to see a rattlesnake?”

For this adventurous animal lover, there’s only one possible answer to that question. So I happily bounded down the hill after ranger John Heiser, coming face to face — from a safe distance, of course — with North Dakota’s only venomous reptile.

The muscular prairie rattlesnake coiled partly under a ledge, camouflaged by the surrounding sandstone. It noisily shook the rattle at the end of its tail and began sliding back under the rock, black tongue flicking. “See, he wants to get away — he doesn’t want to threaten us,” Heiser said.

He should know. During four decades exploring Theodore Roosevelt National Park, a 70,000-acre refuge in the remote Badlands of western North Dakota, Heiser has had many a run-in with park wildlife, which include bighorn sheep, elk, pronghorn, birds of prey, black-tailed prairie dogs and coyotes, as well as bison, perhaps the park’s most popular resident.

A bison, which Theodore Roosevelt called the “mightiest of American beasts,” in the president’s eponymous national park in North Dakota. (Andrew Burton/Getty Images)

That woolly icon of the Wild West features in how the park’s story begins. In 1883, 25-year-old Theodore Roosevelt, a New York City tenderfoot wearing a Brooks Brothers suit, came to what was then Dakota Territory to hunt bison. It was at the time a rare species: Overhunting had rapidly shrunk the herds of the “mightiest of American beasts,” as he called it. Before long, Roosevelt became enamored with cowboy life in the Badlands and bought two cattle ranches, places he’d go to grieve the deaths of his wife and mother, who died hours apart on Feb. 14, 1884.

Concerned by the decline of big game and overgrazing of grasslands, he developed a passion for conservation. Instrumental in halting the bison’s extinction, Roosevelt helped usher in an 1894 law that made it illegal to kill the animal in Yellowstone National Park. In later years, as president, he would set aside 230 million acres of land. He came back to North Dakota once, in 1903, but didn’t live to see his much-loved landscape — including his home ranch, Elkhorn — declared a national park in his honor in 1947. At that time bison no longer roamed the area, so the park service began reintroducing the animals in the 1950s — gradually restoring it to the environment of Roosevelt’s day.

A nature enthusiast myself, I’d come to see critters without the crowds: Just over half a million people visited Theodore Roosevelt in 2014, compared with more than 3 million at more well-known parks such as Yellowstone and Yosemite.

So on a July evening, my fiance, Brian, and I drove into the park’s South Unit — the biggest of its three sections — via Medora, a well-preserved 1880s town that touts itself as the state’s No. 1 tourist draw. It was prime time for wildlife viewing, and before long I spotted a giant black hump through the window: “Bison!” We stopped to watch the lone male graze through our binoculars — no Yellowstone-style bison jams here. Winding past the eroding plateaus of the Badlands, we soon saw another male, rolling joyously (or so it seemed) in the dirt. Later at the visitor center, I learned that many of these bulls live alone, as the animals tend to become more solitary with age.

Continuing north, we passed prairie dog towns, open meadows where the comical little rodents live by the hundreds. I could spend hours watching them pop out of their burrows, paws tucked adorably to chests, or scampering awkwardly about, occasionally pausing to nuzzle a neighbor. A favorite meal for many predators, they’re constantly communicating dangers to one another with chirping noises that sound remarkably like squeaky toys.

Around us loomed a seemingly limitless expanse of striped, weathered rock, punctuated occasionally by splotches of green. The peaks’ reddish tones and barren look gave it a feeling of Marslike otherworldliness, and I could tell what Roosevelt meant by his description of the Badlands as “grim beauty” — a landscape that was mysteriously severe and inviting at the same time.

Eager to explore more on foot, we woke up early for a ranger hike in the Petrified Forest Loop, a part of the park that’s designated wilderness, meaning only limited, non-motorized activities, such as hiking and horseback riding, are allowed. At the gate, park ranger Erik Jensen encouraged us to consider how few people have treaded here in modern times: “It’s neat to get that feeling in this day in age.”

Yet any reverie was quickly interrupted by a steady drumming sound in the distance, which Jensen told us was related to the oil industry. North Dakota is in the midst of an unprecedented oil boom as many companies hydraulic fracture, or “frack,” the Bakken formation, one of the largest contiguous deposits of oil and natural gas in the United States. Evidence of it is everywhere in the region. On our hike, we could even see pump jacks nodding on distant hills.

The industrial sounds faded as we hiked farther across the hot, sunny prairie. The colors dazzled, from silvery sagebrush to dark green junipers to coppery reds and browns of the distant buttes. Bubblegum-pink prairie roses and yellow prairie coneflower, whose blossoms look like miniature sombreros, framed the path. At a trail intersection, Jensen stopped to point out a strangely blank metal plate on a wooden pole: Park bison, he explained, scratch themselves on the poles and rub the trail names and distances off in the process. (More on that later.)

We hiked into a wide valley littered with stumps of petrified wood, trees that had been buried and fossilized eons ago, when the Badlands were a giant swamp. Climbing a hill to see a particularly tall stump, I looked across the valley and noticed the rounded, telltale hulk of a bison, which, as usual, gave my heart a little boost. Jensen told me later that seeing bison never gets old for him, either: “Every time I see them,” he said, “it’s a reminder I’m in a wild place.”

Some of the 70,000 acres of Theodore Roosevelt National Park. The otherworldly terrain of western North Dakota was beloved by the 26th president, who first visited the area at 25 to hunt bison. President Roosevelt eventually made halting their extinction, and wilderness conservation in general, a national priority. (Prisma Bildagentur AG/Alamy Stock Photo)

Our day took a wilder turn at Cottonwood Campground — named for the tall trees that line the nearby Little Missouri River — during an evening park program called “Biological Bad Boys.” White fluffs of cottonwood seed blew about as ranger Jeff Zylland schooled our enthusiastic class of tourists and campers on North Dakota predators. Wolves and bears, the latter of which Roosevelt pursued in his day, had long ago been hunted out of the area, he told us, and only one mountain lion is thought to roam the park. But other wily characters remain: He put up an amazing picture of a coyote and badger hunting together in a prairie dog town, which he referred to as “the refrigerator of the Badlands.” A tourist, I noted with envy, had taken the photo.

But he truly shocked the group with his slide of a prairie dog and the words: “Cute, cuddly, cannibal killers.” Female prairie dogs, scientists have discovered, will sometimes kill their close relatives’ babies, and can be seen fleeing the crime scene with blood-covered faces. “Did I ruin prairie dogs for anyone?” he asked. “Yes!” a girl shouted from the front row. Zylland ended the program with a reminder that Roosevelt ushered in the idea of conservation as protecting the whole ecosystem — as he puts it, “the good, the bad and the ugly.”

Driving back to our cabin that night, we got in a few more good-critter sightings: A male elk, antlers tiered higher than a wedding cake, trotted in front of our headlights, and a colorful herd of feral horses grazed near the road, a tiny jet-black foal with a white blaze romping among them. Our streak continued the next morning when a small herd of pronghorn — arguably North America’s fastest land animal — galloped across the grasslands. Laughing, Brian pointed out a male with some unusual headgear: a huge sagebrush tangled in his horns. “Looks like Lady Gaga of the prairie,” I said.

By our last day in the park, we’d seen many of the usual suspects, plus a bull snake, a mama mule deer with twins, goldfinches and a turkey. The only big-ticket item we had yet to see was bighorn sheep, which only live in the North Unit, about an hour’s drive north, where the people are even fewer and the scenery more grandiose. We set out along the forested Caprock Coulee Trail, dodging squishy bison “pies” as dragonflies darted overhead like little aerial bombers. Hiking up to a ridge, I was admiring the gorgeous Badland views when my stomach lurched: The trail marker had been rubbed blank, just like in the Petrified Forest. Studying the park map as best we could, Brian and I took one trail, only to discover it led to a cliff. After a few nervous minutes, we got back on track — no thanks to itchy bison.

Prairie dogs — more ruthless than they look — are among the may types of wildlife that roam free in North Dakota’s Theodore Roosevelt National Park. (Brian Clark Howard)

Our final North Unit stop was the panoramic Oxbow Overlook, where we looked through our binoculars in vain for bighorn sheep that might be clambering among the rocky buttes. Maybe that’s because there were fewer of them, as many of these acrobatic animals have died recently because of pneumonia transmitted from domestic livestock.

But our luck hadn’t run out yet. On our last drive through Theodore Roosevelt, we rounded a bend and exclaimed at the tableau laid out before us: A bison herd, with animals of all different ages and sizes, smattered across the valley. Cinnamon-hued babies played beside their mothers and massive bulls rested regally in the grass. To top it off, a pair of feisty young males butted heads right in front of us. I struggled to find a word to describe my delight when “Bully!” came to mind. Teddy would’ve surely approved.

Dell’Amore, a digital editor and writer at National Geographic, combines wildlife and traveling whenever possible. You can follow her on Twitter @cdellamore.

More from Travel:

What a Trip: North and South Dakota tourism bureaus, are you hiring?

In North Dakota, searching for her roots and finding a lot to root for

Following Steinbeck to Fargo

If you go
Where to stay

Wannagan Creek Cabins

2440 East River Rd., Medora



Roomy new cabins overlooking the Little Missouri River a short drive from Theodore Roosevelt National Park. $150, two-night minimum.

Rough Riders Hotel

301 Third Ave., Medora



In downtown Medora, this hotel was originally built in 1884 and fully renovated in 2008. Summer rates (June 5 to Sept. 12) start at $189.

Where to eat

Badlands Pizza & Saloon

285 Third Ave., Medora



It’s tough to beat classic American pizza and a root beer after a long day on the trail. Twelve-inch pizzas, from $13.

Boots Bar & Grill

300 Pacific Ave., Medora



Enjoy live country music over tempura-battered walleye. Entrees from $8.

What to do

Theodore Roosevelt National Park

315 Second Ave., Medora



Watch iconic Western wildlife, hike through prairie wildflowers, camp among the cottonwoods, and more. Open year-round. $20 per individual vehicle.

Chateau de Mores State Historic Site

3426 Chateau Rd., Medora



Tour the impressive summer residence of French nobleman Marquis de Mores, who founded Medora in 1883. Open daily Memorial Day to Labor Day from 8:30 a.m. to 5:30 p.m. From Labor Day to Memorial Day, hours are 9 a.m. to 5 p.m. Tuesday through

Saturday. Adults $10, children $5.



— C.D.