CASTLE ROCK — The black Labrador retriever mix with a splash of white on his chest gazes quizzically at the Denver Dumb Friends League volunteer snapping his photo — a freeze-frame soon to be posted online in the hope that his beseeching eyes might connect in a life-changing way with a receptive human.

At 9 years old, he’s mellow and in good health, except for the dental work that will briefly delay his availability for adoption. And he’s road weary from the 14-hour journey that brought him here with a van load of other dogs abandoned, surrendered or otherwise cast off to the Peaceful Animal Adoption Shelter in rural Oklahoma.

His name, for the moment, is Denver. He doesn’t exude the irresistible charm of the puppies that made the trek with him, and once upon a time might have been a tough case for adoption. Yet, within a few days — and just hours after he charms a television audience on a local newscast — he will find a welcoming Colorado home.

“You’ve come to the right place, bud,” says one of the volunteers.

His prospects for living out his dog-years with an attentive adoptive family rose exponentially once the van crossed the state line. He and his 36 fellow canine travelers, except for a few puppies too young to be adopted yet, will find new homes within days. They make up just one sliver of a far-flung pet transport effort that counts Colorado among the most desirable destinations.

Nearly 30,000 documented dogs from out of state, predominantly to the south, made their way in 2016 to Colorado shelters and rescues, where the live-release rate hovers around 90 percent and virtually no adoptable dogs are euthanized for lack of space to hold them.

That number has risen steadily from about 17,000 in 2014 as demand for family pets has led to a patchwork of partnerships between local shelters and rescues with organizations in regions where overpopulation continues to be a vexing problem. In all, 135 registered Colorado shelters or rescues transported adult dogs from out of state in 2016, according to state records, with 90 of them also taking in puppies.

Neighboring states, as well as Texas, Arkansas, Louisiana and other parts of the Southeast, routinely send candidates to capitalize on Colorado’s seemingly bottomless demand. Cats, whose population issues also are gaining increased attention now that state animal welfare groups have gained traction with dogs, account for a smaller fraction of pet transports, with nearly 5,000 coming into the state in 2016. But some look for that number to increase.

Coloradans from pet owners to welfare experts attribute the state’s status as an extremely pet-friendly landing spot to demographic, geographic, economic and cultural factors, as well as a largely successful, decades-long push toward normalizing spay and neuter procedures. A highly educated populace, an outdoors-oriented region and a culture that tends to place significant value on pets as family members coalesced around heightened expectations for animal treatment.

“We believe that years and years of humane education, responding to animal cruelty and neglect and making animals have value in our community has really been successful,” says Apryl Steele, CEO of the Denver Dumb Friends League. “It’s been this step upward for animals in society, and our community has buy-in about the value of animals, especially cats and dogs.”

That demand also drives a downside. While dog shelters and rescue organizations — Colorado now has about 260 registered and an unknown number operating under the state’s radar — have saved thousands of canine lives, concerns arise over some operations that transport animals without required safeguards.

Those imports, particularly from warm, humid regions like the Gulf states where certain illnesses are prevalent, can put Colorado’s animal health at risk of heartworm, distemper and parvovirus, and leave adopters heartbroken and on the hook for big veterinary bills.

“I wouldn’t say there’s an imminent threat,” Steele, who previously headed a veterinary practice, says of the current health risk. “The way disease works, though, when it blows up in your community, it becomes a tipping point. We’re not at that tipping point yet, but we want to be mindful about not getting there.”

Culturally, Colorado has come to recognize pets as integral members of many families, giving rise to more dog-friendly policies among landlords and businesses and creating a burgeoning market for four-legged companions.

That stands in marked contrast to areas of the U.S., primarily in the South, where live release rates in some areas can dip as low as 30 percent — seven in 10 are euthanized, even healthy animals that would be highly adoptable in Colorado. Warmer year-round weather conditions allow stray pets to more readily survive on their own and reproduce, perpetuating the cycle.

Roger Haston, chief of analytics for Arizona-based PetSmart Charities, and other experts stress that the relationship between organizations with a surplus of dogs and those with access to an eager pool of adopters has to extend beyond simple supply and demand to address the root causes of overpopulation.

“Transport is not a solution but a temporary release valve,” says Haston, whose group doles out millions in grants and was an early supporter of the practice. “When we get that collaborative effort, it’s pretty amazing.”

* * *

Every Tuesday evening, the Peaceful Animal Adoption Shelter (PAAS) in Vinita, Okla., a town of 6,000 in the rural northeast part of the state, loads dozens of dogs — and sometimes a few cats — into its specially designed van to begin an overnight journey to Colorado.

The undertaking practically empties the shelter, at least for the moment, and a mobile cacophony of barking subsides as darkness settles in, the dogs calm down and the van cruises north to connect with Interstate 70 in Kansas.

Around 3 a.m., it pulls off at a fenced dog park in Colby, where all the adult dogs get a short exercise break. Then it’s back on board for the run to Castle Rock, where the van pulls into the Dumb Friends League’s Buddy Center parking lot around 9 a.m. to begin processing the pooches for adoption.

One by one, the dogs are introduced to a virtual assembly line where they’re weighed, scanned for identifying microchips, photographed and immunized for any conditions that haven’t already been addressed. Along the way, they soak up the affection of a dozen or more volunteers who relish their roles.

“Cuteness factor of 10!” coos one as the slow parade begins.

The dogs complete the process with an assessment of overall body condition on a scale of 1-9, ranging from emaciated to obese, and they’re checked for possible infections and dental issues that might necessitate treatment.

Denver, the 9-year-old lab mix, has a broken and discolored tooth that needs to go, but he registers a good score of 4 on body condition and a strong heartbeat. A few days later, once the dental issues are resolved, he goes up for adoption — and quickly establishes his Colorado residency.

Meanwhile, the two PAAS drivers get a few hours sleep at a nearby motel before heading back to Oklahoma, where the process that sent about 1,600 dogs to Colorado last year will be repeated the next week.

“We have a severe pet overpopulation problem in our state,” says Rhonda Norris, the PAAS veterinary technician who oversees the transfer program and sometimes drives the route herself. “A lot of them are strays, or owner-surrenders. We don’t really know what their stories are. Because of overpopulation, it’s imperative we get them out as quickly as we can, so they’re not at risk for euthanasia.”

[ Related: From an Oklahoma dog shelter, Moon Pie migrated to Colorado — and found a future as Kadie ]

The partnership with the Dumb Friends League, in its second year, grew out of desperation. PAAS, which opened a new building prepared to serve as an adoption agency, quickly discovered it was fighting formidable headwinds. Within a month and half, the building was full of dogs, with 100 more waiting to come in. There were plenty of cats, too.

But nobody was adopting.

Kay Stout, executive director of PAAS, reached out to the Denver Dumb Friends League, which agreed to take some of Stout’s dogs — but only on a trial basis to see if the shelter could ensure the health and behavior of the animals and, ultimately, follow a strict protocol.

PAAS proved itself a trustworthy partner, and the transfers continued on a regular basis, easing overpopulation across a wide swath of the Midwest, as the organization developed relationships with a web of about 40 other rescues and municipal shelters that stretch across rural Oklahoma and into Arkansas and Missouri. They all funnel dogs to Colorado through the Vinita operation.

“The success of it is because of the protocol they established that we require of our partners,” Stout says. “It took awhile for us to play by those rules. They were rules we’d never played by.”

For one thing, the shelter had to be certified by the Pet Animal Care Facilities Act, the licensing and inspection program within Colorado’s Department of Agriculture that since 1996 has monitored transfers and pet care facilities. As the number of rescues has grown, including unregistered operations, so has PACFA’s workload.

Last year, the agency fielded 911 consumer complaints — a nearly 270 percent increase from 2015 — on both licensed and unlicensed operations. About 400 of the complaints targeted unlicensed facilities, with 135 enforcement actions zeroing in on rescues, 80 on shelters and 15 on pet transporters.

“One of the issues with rescue groups is kind of a ‘dog flipping’ business,” says Nick Fisher, PACFA program manager. “They bring dogs in Thursday, adopt them out on Saturday. The adoption contract usually states that you adopt them ‘as is.’ If they’re sick, there’s not a lot of support if you run into any issues.”

The PAAS shelter in Oklahoma, which began its regular weekly runs in April of 2016, has proved a reliable partner. The Dumb Friends League agreed to invest in spaying and neutering the animals transported from Vinita and implanting microchip identification, as well as taking on some of the harder cases — dogs with medical or behavioral issues that once would have resulted in euthanasia. PAAS would do its part to make sure the animals were vaccinated and not behavioral risks.

But the eventual goal, Steele says, is to promote social change in the source community, namely to encourage people to place a greater value on the animals. Depending on the partner, DDFL might invest in local spay/neuter or vaccination efforts, or general humane education.

“When you have mitigated your stray problem, you have healthy animals in your community, people experience a positive human-animal bond and they value animals more,” she says. “By taking animals out of the community, we’re impacting that oversupply that creates undervalued animals.”

A number of larger pet welfare organizations have partnered with out-of-state groups to transport dogs, including the Humane Society of Boulder Valley, which last year brought in about 1,100 from out of state.

“As more and more of us across the country are doing transport, in a way we’ve gotten the low-hanging fruit,” says Lisa Pedersen, CEO in Boulder. “We’ve moved vast number of animals from one community to another. Now, there are harder questions for us to be looking at. Transport is one tool, but you have to get to the core of what’s happening in those communities. What’s happening to animals is a barometer to other issues in the health of a community. It’s getting more complex.”

Many of Boulder’s transport dogs come from Houston, where the Rescued Pets Movement — dubbed RPM — partners with the city pound to find homes for its surplus animals.

RPM director Katie Beirne, recalling a life-changing trip to Colorado two years ago, marveled at the empty space in local shelters, in stark contrast to Houston, where there was never an empty kennel. In public, she saw dogs wherever she looked — and people eager to adopt.

“I could not believe it,” she recalls. “People take their animals everywhere. And they’re not all purebred — so many mutts were part of the family. I went to an adoption event at Petco, and there were lines of people waiting for animals. It was like Black Friday after Thanksgiving.”

In 2012, she says, the Houston city pound’s live release rate was below 50 percent but now has improved to about 86 percent. Nearly one-third of the rise she claims for RPM, whose Colorado connection plays a key role along with other transports to the Pacific Northwest, the Northeast and even Canada.

“It became clear the culture in Colorado is more prone to adopt and own a rescue animal,” Beirne says. “The culture in Houston is the perception that shelter dogs are broken, that they can’t be trusted, and that leads people to buy from breeders.”

* * *

Even Colorado shelters far removed from the Denver metro area, like La Plata County Humane Society in Durango, also serve as a conduit that not only sends dogs from their own area to the Front Range but dogs from other states as well. Director Chris Nelson takes in up to 700 a year through what he terms a “pipeline” from the Southwest and Texas. Most find homes in the Durango area, but last year he sent about 40 to the Denver-Boulder area.

His shelter progressed from a 30 percent euthanasia rate in 1997 to less than 2 percent now, reflecting spay and neuter awareness that has lifted the entire state.

If Coloradans are quick to open their homes, Nelson adds, they’re also ready to open wallets when a story touches them. He recalls the case of a German shepherd puppy named Lieutenant Dan, who appeared to be paralyzed and was about to be euthanized when workers discovered he actually had feeling in his leg. A plan was hatched to put the dog in swimming therapy and raise money for a wheelchair that would make him mobile.

They put the story on Facebook and reached out to some TV stations. In a week, $32,000 poured in — with $20,000 of that from Front Range communities. The money paid for the wheelchair, but also for orthopedic procedures on four other dogs and more surgeries over the next couple of years.

“It doesn’t work if you do it every week,” Nelson says. “But if you’ve got the right story, it helps.”

It doesn’t hurt the cause that more and more people have found companionship with dogs that come from rough — or maybe just indeterminate — beginnings.

Nelson, the director of the Durango shelter, figures the same people who used to crave Golden Retrievers now find a certain cachet in adopting rescue dogs. He calls it the Katrina Phenomenon. People would call him wanting to adopt dogs transported after the 2005 hurricane and he’d tell them that while he didn’t have any of those, he did have dozens of other wonderful dogs ready to go.

But I want one from the flood, they’d respond.

“I got tired of hearing people say that,” Nelson says. “So I said, ‘Look, I’ll leave the water on and plug the sink, and by morning they’ll have survived a flood.’ They didn’t think that was too funny. They want a story, because that makes for good conversation. In reality, every dog’s got a story.”

But Katrina did provide some impetus for figuring out how to move animals across the country, whether by ground transport or even flight groups like Pilots N Paws. That organization provides information on pets in need of transport to a list of about 6,000 pilots in all 50 states. Some groups even move dogs from outside the country, from places like the Dominican Republic or, more recently, hurricane-ravaged Puerto Rico.

The paradigm shift that has made Colorado such an enthusiastic home for so many cast-offs from other states eventually will spread, figures Nelson, the director of the Durango shelter, raising the profile of pets as family members.

“As jaded as I am about humanity in this job, I think culturally we’re changing,” he says. “Even if the trend of getting a rescue or shelter dog will fade, it’ll be strong enough to last generationally. My mom didn’t want dogs on the couch. Her mom didn’t want them in the house. We’ve changed as a society, for the better.”