Barn Hunt, in which your pooch must navigate tunnels in bales of hay or straw to find live rats hidden (safely) in sealed tubes, is the country's fastest-growing dog sport, organizers say.

Why it matters: When dog owners train their pets to participate in sports — like agility and obedience — it gives them fresh purpose and enthusiasm and deepens the human-animal bond.

How it works: In Barn Hunt, dogs are trained to run an obstacle course that's studded with live rats (in aerated PVC tubes), plus empty tubes that may or may not smell like rat.

• Dogs have to jump onto scratchy hay bales and crawl through dark, winding tunnels to find an ever-increasing number of hidden rats. (See a video.)
• The rats are pets that are said to enjoy the interaction with the dogs — and officials called "rat wranglers" ensure they're treated humanely.

What they're saying: "I came up with Barn Hunt as a way to test breed instinct," Robin Nuttall, the founder of the sport and head of the Barn Hunt Association, tells Axios.

• "At its core, Barn Hunt really is a test of the working instinct of breeds that were bred to eliminate rabbits."

"Our rats are bred by show rat people who have looked over Barn Hunt and decided that it is very safe and humane," Nuttall adds.

• "They're bred for really outgoing, friendly temperaments — we don't want an animal that is scared and is going to bite everybody."

State of play: Barn Hunt, developed 11 years ago, was recognized by the American Kennel Club (AKC) in 2013 and has a system of tournaments and championships.

• There are now 250 Barn Hunt clubs in the U.S. and Canada and 65,000 registered dogs, according to the Barn Hunt Association.

Driving the news: The sport's growing popularity helped prompt Jenny Carragher, a former private equity executive, to open New York City's first Barn Hunt facility last month: Sniff 'n' Seek, on the Upper East Side.

• "The reason I'm doing this is because it has really benefited my dog," says Carragher, who has a 9-year-old Italian Greyhound named Felix.
• Felix "was bored and needed a job," she says. "I watched him transform — he became much more confident."
• Her pet rats, Peaches and Trixie, gamely engage with her four-pawed clients. "They are totally safe and actually play with the dogs."

At a recent introductory class, Carragher showed her clients how Barn Hunt works.

• "Your dog has to climb on a bale of hay, crawl through a tunnel and find a rat," she said.
• Nic Celenza, a veterinary technician from Brooklyn who heard about Barn Hunt on TikTok, came with her 7-year-old Chihuahua/pug mix, Mochi.
• Mochi is "super energetic, but she struggles with impulse control," Celenza said. "She needs more mental stimulation than most people would expect."
• Henry Kaye, a designer and musician from Brooklyn, brought his 1-year-old Corgi, Twiggy, because "it's winter and I need something to keep her sane."
• "She is bred over thousands of years to herd sheep," he said. "There are so few outlets in the city."

Backstory: Barn Hunt is based on the traditional "rat catcher" role of certain dog breeds — notably terriers.

• Some breeds were developed specifically for the job, though all dogs may participate in Barn Hunt (as long as they can fit in an 18-inch hay tunnel).
• Dogs also were used in the trenches during World War I to help control rats, which were a big danger to troops — and they're used today to control rats in the alleys of New York City.

Yes, but: PETA and others have raised ethics questions about Barn Hunt's use of rats, and whether the animals are frightened or mishandled.

• Nuttall and Carragher say that animal welfare is their highest consideration and that the rats seem to enjoy the sport.
• Nuttall says that the pet rats participating in Barn Hunt tend to live longer than those that don't "because they're very well cared for, and they're not stressed."

Zoom out: There's an ever-increasing number of sports that people do with their dogs, the most familiar being conformation (to breed standards — i.e. dog shows), obedience and canine agility.

• More exotic sports include flyball, rally, dock diving and Scent Work.

The bottom line: Nuttall says that Barn Hunt is the fastest-growing dog sport.

• "Last year alone, we had over 7,000 dog registrations and 561 trials across the U.S. and Canada."