Romania is poised to put down thousands of strays. Animal rights activists are outraged, but the diseases dogs spread are a deadly threat to humans and wildlife.

In the face of protests that the plan is “criminal” and “inhumane,” Romania is about to begin a program to catch and euthanize its feral dogs. The proposal arose from growing alarm over the 64,000 feral dogs said to be roaming the streets of Bucharest, and the 7,800 dog bite injuries in the city so far this year. It gained momentum last month after a stray dog mauled a four-year-old boy to death. 

Legislation authorizing the culling—for dogs not adopted after 14 days—has already cleared the Romanian parliament and been approved by the national court. It now awaits the signature of President Traian Basescu, who has said that "humans are above dogs."

Predictably, animal rights activists are outraged. The World Society for the Protection of Animals has criticized the culling as “both inhumane and ineffective." Vier Pfoten, a Romanian animal welfare group, calls it “mass killing,” arguing instead for continuing a program to catch stray dogs and sterilize them.

It’s easy enough to understand where the animal welfare activists are coming from: I love my dog, too. The debate also matters because it isn’t just about Romania. Problems with stray dogs are happening everywhere from Detroit, which has 40,000 feral dogs, to Srinigar, India, which has one feral dog for every 13 people.

But instead of automatically opposing the euthanasia idea, it’s worth pausing to think more clearly about what animal welfare really means. Leave aside the question of whether a life on the street is any kind of life for a dog. Beyond that, feral dogs are also catastrophically bad for wildlife. 

The evidence of the damage they cause makes for grim reading. But it is compelling. Let’s start with disease. Dogs can carry and transmit more than 40 deadly pathogens to wild animals, including rabies, canine distemper, parvovirus, and Rocky Mountain spotted fever. They’ve caused agonizing deaths among endangered gray wolf puppies and black-footed ferrets. Ethiopian wolves, down to just 500 individuals, have suffered three devastating rabies epidemics because of feral dogs. That has forced biologists to undertake the difficult and potentially dangerous step of capturing and vaccinating those wolves that seemed likeliest to come into contact with dogs.

The diseases that dogs spread are also a deadly threat to humans. In India, for instance, feral dog populations increased by up to nine million animals beginning in the early 1990s, as a scavenging niche opened up because of the near-extinction of vultures. That caused a dramatic rise in dog bites and rabies incidence. As a result, an additional 48,000 people died over a 14-year period, according to a 2008 article in Ecological Economics, which put the resulting loss to the Indian economy at $24 billion. Moreover, the threat isn’t just from diseases we already know; frequent contact between dogs and wildlife also means they are one of the likeliest means by which some emerging pathogen could make the deadly leap to humans.

Feral dogs also threaten wildlife far more directly. A 2011 article (“Is Wildlife Going to the Dogs?” in the journal Biosciences documented numerous cases. In Kazakhstan, feral dogs kill more than 10,000 saiga deer annually. In the Galapagos Islands, they take unsustainable numbers of marine iguanas. In the United States, they kill more wild turkeys than perhaps any other predator. In New Zealand, a single dog, not feral but allowed to roam free by its owner, killed up to 800 kiwi—the small, defenseless birds that are the national symbol—over a period of just six weeks. In Brazil, feral dogs kill and consume small mammals, competing for prey with native predators. And in the Pyrenees Mountains of France, dogs commit the vast majority of the attacks on sheep and other livestock—but wolves and brown bears take the blame (sometimes from the barrel of a gun). 

You get the idea. What to do about it? Scientists have called for public awareness campaigns to help dog owners understand the threat to wildlife. In New Zealand, for instance, a campaign to discourage owners from letting their dogs roam free at night helped in the recovery of kiwi populations. Romanian animal welfare activist Gabriel Paun of Vier Pfoten has prudently argued not just for continued sterilization of feral dogs, but also for a change in the culture of pet ownership, including microchipping of dogs. That way, owners could be traced and penalized if they abandon their dogs. 

But microchipping, like sterilization, can be costly for many, especially in developing nations. And none of these measures would do much to reduce the immediate and increasing menace of feral dogs. Catching the dogs and offering them for adoption may sound like a practical alternative. But dogs that have been living on the street for long periods typically don’t make great pets, and animal welfare groups have been more successful so far at drumming up outrage than at bringing in families willing to adopt. Until that changes, euthanizing—no, let’s not mince words—killing feral dogs is the best hope for beleaguered wildlife.

- Richard Conniff has written seven books. His articles appear in Smithsonian, NYT Magazine, National Geographic, and more.