We now view pets not only as family members but as equivalent to children,” said James Serpell, an emeritus professor of ethics and animal welfare at the University of Pennsylvania School of Veterinary Medicine. “The problem is, dogs and cats are not children, and owners have become increasingly protective and restrictive. So animals are not able to express their own doggy and catty natures as freely as they might.”

The health risks begin with breeding, of course. One of the most popular dog breeds in the United States is the French bulldog, a member of the brachycephalic family of flat-faced dogs that bond well with people but have trouble breathing, among other severe health problems.

But we are also changing our animals’ relationship to their surroundings. Out of concerns about bird predation, many cats now spend their entire lives inside. Until the late 1970s, even city dogs spent most of their time outdoors, either in backyards or roaming unleashed around the neighborhood. Now, said Jessica Pierce, a bioethicist in Colorado whose work focuses on animal-human relationships, “the unleashed and loose dog is considered against the natural order of things.”

One of the fastest growing market segments is the so-called pet confinement sector, which includes crates and indoor fencing, as well as head harnesses and electronic collars. “The level of constraint that dogs face is profound,” Pierce said. Although dogs several decades ago were more likely to be hit by cars, she added, “those risks were outweighed by the freedom of experience and movement.”

The modern pet paradox, in a nutshell: “Owners don’t want dogs to act like dogs.” Serpell said.

While dogs are allowed in an ever-increasing number of human spaces — restaurants, offices, stores, hotels, as well as more parks with designated dog runs — their growing presence has not translated into greater independence.

The confinement and isolation, in turn, have bred an increase in animal separation anxiety and aggression, Serpell said. Roughly 60% of cats and dogs are now overweight or obese. And due in part to the burden and expense of modern pet ownership — veterinary fees, pet sitters, boarding costs — more people are abandoning animals to animal shelters, leading to higher rates of euthanasia. In 2023, more than 359,000 dogs were euthanized at shelters, a five-year high, according to Shelter Animals Count, an animal advocacy group.

“We’re at an odd moment of obsession with pets,” Pierce said. “There are too many of them and we keep them too intensively. It’s not good for us and it’s not good for them.”