The stress of transport not only makes animals susceptible to disease but can also contribute to behavioral problems. The dogs have often been abused, neglected or feral before they land in a crowded and cacophonous shelter. And then they get loaded onto a truck or airplane and transported hundreds or thousands of miles to another shelter or foster home before they are eventually adopted. A loving home at the end of the line sometimes isn’t enough to make up for all that trauma.

“As the years have gone by with the transport system, I started seeing so many unsocialized dogs that were aggressive or scared of their own shadows,” said Kelley Bollen, an animal behaviorist in Reno, Nev., who consults with shelters and people who have adopted rescue animals. While some animals are resilient, others are not. “It’s heartbreaking to have to explain to people who have just rescued this dog from the South that this animal won’t be a normal pet,” she said. “I tell them, ‘We’re going to work really hard to get this animal comfortable in your house with your family, but it’s going to be a rough road that’s going to take patience, drugs and a lot of understanding.’”

All this has led many animal welfare advocates to question the wisdom of “humane relocation” and whether all the money that goes toward marketing, bundling and ferrying animals might be better spent stemming the flow of dogs into shelters in poor communities. Since up to 80 percent of dogs that end up in shelters are surrendered by their owners or turned in as strays, there has been a growing movement to address what’s preventing people from caring for their pets.

One example is the nonprofit group Emancipet in Austin, Tex., which focuses on providing free or low-cost spaying and neutering and veterinary services. The group also goes door-to-door to answer people’s pet-related questions.

“Ninety-nine percent of people have pets because they love them and will do right by them if given education and the opportunity,” said Myles Chadwick, the group’s vice president of consulting and training. Emancipet treats some 100,000 animals per year and has contributed to a significant decline in Austin’s shelter population.