Long-haul transfers of dogs from one state to another are not regulated and there are wide variations in how the animal transfer programs are run, said Kate Pullen, director of animal sheltering for the Humane Society of the United States.

“Some are well-structured, with good decisions on both ends,” Pullen said, but there are “some really disastrous situations” in which animals in transit are deprived of food or water or become sick and die en route.

To prevent dogs from succumbing to stress on long trips, Colorado’s Humane Society of Greater Boulder sets limits on how long and how far the dogs can travel. The limit for puppies is eight hours or 500 miles, for older dogs 12 hours or 700 miles.

The Boulder shelter accepts about 1,900 dogs a year from a wide area that includes Wyoming, Kansas, Nebraska, Oklahoma and New Mexico, said Connie Howard, the society’s director.