Is there an ethical way to kill rats?

The place: a modest house at the end of a narrow street in Culver City, California. The problem: The house’s owner had been feeding bread to a population of rats, which had moved into her kitchen and living room and then into the ceilings, where they had begun encroaching on the neighboring tenants from above. The diagnosis: “Unbelievable,” said Dave Schuelke, a buff and ruddy-faced exterminator who is one-half of the pest control and home repair company Twin Home Experts. “I’ve never seen this before.”

Schuelke was speaking breathlessly to a camera that he had trained on himself. He was alone behind the house, but his intended audience was the nearly 250,000 subscribers of the Twin Home Experts YouTube channel, where he and his identical twin brother, Jim, post videos of themselves on the job. Nine years ago they began uploading videos about general home repair, but more than 70 million views later, their content has skewed toward rats.

“People want to see that type of gory-looking stuff,” Dave Schuelke said, setting down the camera. “People want to see the action.”

Reasons for controlling the urban rat population are abundant: The animals can spread diseases to humans, destroy property, and damage native ecosystems. But rats are also cognitively advanced social animals, and questions about how to effectively control them can raise tricky ethical questions. Glue traps will leave rats starving, for days, before dying. Poison leads to a slow, painful death and can endanger other wildlife. Standard wooden snap-traps often catch the limbs or tails of the rats, who will gnaw off appendages in desperation. Live-catch traps are tricky to execute, and, when many rats are stuck in the same place together without food, they can eat each other.

Even if rats were extracted from an urban environment, what do you do with them? Release them into the woods, where they can damage existing ecosystems. Keep them as pets? Rats are reviled but resilient; dangerous but inculpable. “Right away, you end up in a very uncomfortable position,” said Robert Corrigan, a New York City rodentologist who has studied urban rats for decades. “There’s no way to get out.”

Where the Wild Rat Traps Are

The Schuelke brothers, along with a handful of employees, had been moving around the house in Culver City for about three hours, looking for rat nests and openings through which the animals could squeeze. The twins’ strategy was to close off every rat entry and exit point and lay traps around the house as the animals grew hungrier and more desperate.

But the whole place was compromised. Holes in the roof, the walls, the floors. The house’s owner, an 82-year-old woman named Ann Chung, said that she could hear rats underneath her at night. She expressed a kind of fondness for the animals — she was feeding them twice a day. But rats were now shredding her collections of newspapers, books, and clothes and staining her carpets twice over with urine and grease. “I am defeated in life, in everything now, because of these rats,” Chung said.

There are more than 4,400 mousetrap patents in the United States, but it is difficult to find designs specifically for catching rats — most are just bigger mousetraps. Rat infestations are also often more of an industrial undertaking than mouse infestations are, less of a do-it-yourself project and more of a job for professional exterminators, who are better at reusing traps. Partly because of this, Woodstream, the country’s largest rat and mousetrap manufacturer, sells some 60 million mousetraps a year and 9 million rat traps, according to Miguel Nistal, the company’s president and CEO. Most of these are the classic wooden spring-loaded snap trap, which Woodstream sells under the brand name Victor.

Nistal said that the main complaint he received about his rat traps was simply that they did not kill rats. Mice are relatively uncomplicated pests; they go for whatever food source is available and, because they’re small, they are easy to dispatch. But Nistal said that, according to his company’s research, only about 65% of the rats that triggered snap traps died. They will wriggle free or outsmart the trap, swiping the bait out safely. Rats are also wary of new things, like traps. “When you and I are gone, and there’s nothing else on Earth, there will be roaches and rats,” Nistal said.

Nistal said that he kept track of “consumer pain points” to help guide further development. Efficacy is one, but other considerations include reusability, keeping the dead animals out of sight, and remote notification that a trap has been activated. To address these needs, Woodstream has developed dozens of traps that fall into three basic categories: glue traps, spring traps, and electric traps. Most of the company’s sales, though, come from the classic Victor spring snap trap, which was invented in 1897.

What Makes a Rat a Rat

The primary species of rat in both New York and Los Angeles is Rattus norvegicus, the brown rat: a midsize rodent with a whiplike tail that is resilient, intuitive and remarkably fecund. (One study found that female brown rats in a Brazilian favela produced 79 viable offspring a year on average.) Brown rats live in colonies and establish networks of tunnels in which they play, groom one another, and touch noses in acts of recognition. They also have a large collection of facial expressions and can sense the emotions of others in their colony. Perhaps in part because of this, brown rats have been found to consistently prefer rewards that benefit others, as opposed to just themselves.

Much research on rat cognition has focused on lab rats, which are bred for experimentation. But Michael Parsons, an urban ecologist at Fordham University who has spent two decades studying city rats, said that wild brown rats (as well as the smaller and rarer black rats) were even more advanced than their laboratory counterparts. “They have unique personalities, and they experience regret, remorse, and social justice,” Parsons said.

Corrigan, who has lived and slept in barns full of rats to better understand them, concurred: “They’re intelligent animals, they make decisions, they regret when they make decisions, they’re altruistic — everything we have going, they have going.”

Erin Ryan, who works for the British Columbia Society for the Prevention of Cruelty to Animals in Vancouver, Canada, has spent years studying rodent traps and thinking of ways to establish a citywide control program that minimizes harm. “What I’ve learned in my research is that humane means something different to everybody,” she said. “But there’s always a time and place for lethal control when it comes to rodents.” It’s simply unsafe to catch and release hundreds of rats.

Corrigan is often hired for large, complex infestations and designs programs to help control rodents. He can end up dealing with hundreds of rats living in the walls of a dormitory or in the basements of buildings. When that happens, he said, it’s an “all-out war to eliminate a very real, substantial risk to human health and safety.” But in the end he has to kill animals that he has spent his whole career studying. Years ago, Corrigan started writing about the contradictions of treating rodents humanely, and it was the most difficult thing he had ever tried to put into words. “Can we, as humanity, be humane to this animal?” he said. “The answer is a very cold, hard no.”

This article originally appeared in The New York Times.