SALT LAKE CITY — It was late in the day for muskrats to be out on Mill Creek, or at least the stretch that runs between a parking lot and a playground near the southern limits of the city. But there they were, two of them, one big and one small, paddling back and forth past each other like furry ships in the afternoon, seemingly unaware they were being filmed.

“They’re so cool, like little beavers,” said Maggie Carter, standing on the riverbank. She held a small camcorder and was staring at its monitor, which displayed a tight shot of the larger muskrat.

Her husband, Joseph Carter — 37, short blond hair, wearing black waders over jeans and a T-shirt — walked over with a GoPro camera strapped to his chest and a cage in his hand.

“They must be messing with each other, they wouldn’t be coming out like this otherwise,” he said, setting the cage down gently. Inside, an animal flicked its head from side to side, swiveling around the small space. It was an American mink, named Boon. Mr. Carter, who was now opening the door to the cage, is among the country’s more unconventional midsize-pest control specialists, known to his 1.3 million YouTube followers as the Mink Man.

Muskrats burrow into river banks, creating holes that can pose tripping hazards at a crowded park. But poison would contaminate the water, and traps can be a safety risk. Plan C: Trained mink. Mr. Carter, who proposed the idea, is one of the few people who has trained mink. Muskrats, rats, raccoons, beavers, groundhogs — if your problem is big enough, and wild enough, the Mink Man might just take care of it at no cost.

“Let’s settle this dispute with form,” he said, watching as Boon, a black torpedo of fur, slipped under the water. With barely a ripple he sped toward the larger muskrat, which began paddling away desperately. Mr. Carter ran along the riverbank, his face lit with energy. “Boon!” he yelled. “Here here here here here here!”

The mink immediately switched directions — as if it understood — and closed in on its prey. Ms. Carter, running behind her husband, tried to keep the camcorder focused. “Are you getting this?” Mr. Carter yelled back to her. “Did you get that?”

Training Your Mink

The Mink Man’s house sits at the end of a cul-de-sac on the outskirts of Salt Lake City. It is full of life: three daughters, a snake in the basement, a fish tank in the living room, ducklings in the sunroom, a rabbit in the girls’ bedroom and a sheep tied to a shed in the yard. Four dogs wander the premises seeking attention.

Out back is where the mink are kept, two dozen of them. They live in large cages, lined up side-by-side, with deep buckets of water for swimming and long tree limbs along the sides of the enclosures for climbing. One cage per mink — otherwise they’ll kill each other, Mr. Carter said.

American mink are territorial, aggressive predators. They have razor-sharp teeth, button eyes and a body shape that calls to mind a chunky squirrel. But they are quick and agile, and their prey can include everything from fish and rabbits to birds and muskrats. Mr. Carter builds his cages with two layers of wire to prevent a child’s fingers from slipping though, and he has “mink-proofed” his yard with slick fences and buried wire around the perimeter for when he lets them out.

Mr. Carter grew up training animals. When he was 9, he bottle-raised a squirrel; at 15, he moved out of his parents’ home and in nearby with his grandfather, who was a famous rodeo cowboy turned show-horse trainer. There, he started training raptors. Toward the end of high school, he moved near a number of mink farms, where the animals are raised for fur. He grew curious.

“Pretty much everyone I asked, they told me the same thing — ‘They’re the most vicious, horrible animal alive,’” Mr. Carter said. “‘They’re completely untamable, untrainable, and it doesn’t really matter what you do.’”

So, in 2003, he decided that he would start taming mink. He quickly succeeded.

“He has that sort of effect with animals, even those that don’t know him,” his wife said. “They either fear him or they respect him.”

In 2014, after a decade of trial and error, Mr. Carter self-published a 242-page book, “The New Sport of Minkenry: The Art of Taming, Training, and Hunting with One of Nature’s Most Intense Predators.” Invoking his experience with falconry, he detailed a number of different techniques to control and care for mink — how much to feed them; how to get them to listen to you; how to teach them to cache, or bring back their prey.

When asked about his training methods, Mr. Carter offered some science and some intuition: Start with the mink when they’re young, make sure to reward them when they’re obedient, be patient. More than anything, you must be a good observer. What kinds of things motivate the animal? Does it have a strong “prey drive?” How confidently does it walk around? What kind of things freak it out?

“You can’t control, you can’t change the genetics of an individual,” he said. “But you can, with the environment, slightly change their view of life.”

In 2013, María Díez-León, now a biologist at the Royal Veterinary College in London, was doing research on captive mink for her doctoral thesis. She and her colleagues had been trying to train mink to recognize certain patterns, without much success. “I think we were not smart enough to understand how the mink were perceiving cues we were giving to them,” she said. “They’re quite inquisitive, and their attention span is very short.”

She stumbled across one of the Mink Man’s videos on YouTube and sent it to her lab group. Mr. Carter was teaching one of his mink, Missy, to cache, using the magic bullet of mink training: a string tied around a dead animal. He ran around his backyard bouncing a dead pigeon a couple of feet above the ground, and Missy gave chase, springing into the air until she had sunk her teeth into the bird and dragged it back to the cage.

“Good girl!” Mr. Carter said, giving the mink a morsel of meat. Had it failed to bring the bird to the cage, he would have refused to play for half an hour or so as punishment. He quickly grabbed another string. Turning to the camera, he said, “Now, she gets a second reward. She gets to chase the rat!”

Dr. Díez-León noted to her colleagues that their own training tasks were probably too easy and their rewards too boring for mink, who, she said, “are quick learners.” The Mink Man’s techniques, the group decided, were superior. “We had no doubt the mink were capable of learning, they are smart creatures,” she said. “It was just great to see that they could.”

The Good Mink Life

Boon quickly caught the Mill Creek muskrat. He wrapped his body around his prey, and together they formed a ball of wet fur: half black, half brown, yin and yang, life and death.

Mr. Carter splashed into the water to pick them up, holding the desperate ball in front of him by the muskrat’s tail. He wrestled the prey from Boon’s jaws and immediately presented a wad of ground meat. “Good job, Mr. Boon,” he said. Ms. Carter walked over with her camera and zoomed in on the dead muskrat, now on its back with its feet in the air.

The minkenry book did not sell well when it was released, but that didn’t bother Mr. Carter. He was working as a financial adviser at the time, and his YouTube account, which he started in 2008 to document his mink, was steadily growing. Around 2017, shortly after the birth of his first daughter, he and his wife decided he would quit his job and start working full time as the Mink Man.

Five years later, the channel serves as an amalgamation of animal-centered home videos and hunting trips. His most popular videos, which have tens of millions of views, are ones with titles such as “Mink vs Rat THUNDERDOME!!!” and “eRATication! RECORD BREAKING Pest Control Job With Dogs!” These are mixed in with videos that, for instance, document the rearing of Boon, starting from when the mink was just a couple of hours old. Mr. Carter’s oldest daughter can be seen kissing baby Boon on the head, or leading a teenage Boon to his cage. These have far fewer views.

The number of YouTube views correlates directly with the amount of money Mr. Carter makes, as advertisers pay the company to be promoted before his videos. The lucrative potential of interspecies showdowns has inspired him to build up a small base of farms and public areas where he can go to hunt rats and muskrats.

“His results are incredible,” said Jordan Timothy, who runs a canal for the North Jordan Irrigation Company in Salt Lake City, which Mr. Carter patrols regularly. Muskrats, rats, raccoons and beavers erode the banks of the canal, just as they do at Mill Creek, where local park supervisors have used the Mink Man’s services for nearly a decade. “He might as well be a trap that’s already set,” said Mr. Timothy. “He’s just so good at what he does.”

To Mr. Carter, the hunting, while popular among viewers, is also for the mink. He buys many of his animals from fur farms, which, in the United States, typically produce a few million pelts a year and have been a source of controversy among animal rights supporters. More recently, they drew attention when mink began contracting Covid-19; in Denmark, in 2020, 17 million farm mink were culled out of fear of spreading the disease. Animals on these farms are often kept in small cages and are killed before they reach their first birthday, while wild mink usually live three years. “I give them a new life,” Mr. Carter said.

The issue, for scientists, farmers and activists, is that it is difficult to know what makes a mink’s life a good one. You can’t ask a mink whether it is happy, or whether it feels fulfilled.

In one study, published in Nature in 2001, animal welfare scientists tried to establish a metric indirectly by measuring how strongly mink pushed on doors standing between them and things they wanted, like food, water, toys or more cage space. “Our results indicate that fur-farmed mink are still motivated to perform the same activities as their wild counterparts, despite being bred in captivity for 70 generations,” wrote Georgia Mason, who led the research. She also found that mink that were deprived of swimming water were as stressed as those that were deprived of food.

Dr. Díez-León, who was Dr. Mason’s student, said that much else beyond this is a mystery. All told, she said, because Mr. Carter takes animals from farms, “the welfare of those mink is better.” She added, “It’s like any thoroughbred horse, or performance animal — or birds of prey who go out hunting. If asked, they probably would prefer to hunt.”

Mr. Carter has his own theories. He prays for his mink before going to sleep (he is a member of the Church of Jesus Christ of Latter-day Saints) and talks to them in a way that, he said, makes them feel almost human.

Almost. After the hunt at Mill Creek, leaning against his white Toyota Tundra with two dead rats in his vest pocket, Mr. Carter looked at Boon, curled up in his cage in the truck bed.

“Animals don’t have ethics,” he said. “They have sensation, they can feel pain, they have the ability to learn, but they don’t have ethics. That’s a human thing.”