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Experts examine ethics of lethal animal population control in CA

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Monday, June 9, 2025   

By Amy McDermott for the Proceedings of the National Academy of Sciences.
Broadcast version by Suzanne Potter for California News Service reporting for the Pulitzer Center-Public News Service Collaboration.


Wildlife biologist David Wiens was extremely nervous the first time he shot an owl. He steadied himself in the evening darkness of an Oregon fire road, pointed his shotgun at a big barred owl perched on a stump, and pulled the trigger. Nothing happened; the gun's safety was still on. "I had to completely recollect myself," he recalls. "The bird just stayed there." Wiens thought back to the months of firearm training preparing him for this moment, resettled the gun's viewfinder on the owl, then pulled the trigger.

Wiens, who works for the US Geological Survey (USGS) in Corvallis, is head biologist of a six-year experiment culling barred owls from areas of Oregon, Washington, and Northern California. Researchers wanted to know if removing barred owls would help another species, the threatened spotted owl, survive.

Management methods that involve killing animals are called lethal control. It's often assumed that reducing the population of one species will help another survive-for instance, killing invasives to protect natives, or culling predators to benefit livestock. Millions of animals are destroyed by lethal control every year in the United States, including coyotes, raccoons, feral cats, prairie dogs, bears, and mountain lions.

Deciding which animals should live or die is not so clear-cut, and context matters. For example, the barred owl is native to North America but expanded beyond its historical range alongside human development. Are they invasive? It depends on whom you ask. Search the literature, and you'll see trade-offs and ethical distinctions between killing invasive species to protect natives and killing native predators, such as wolves and mountain lions, to benefit ranchers.

In general, the public is more comfortable killing exotic, invasive species (think: pythons in the Everglades) than with killing native predators, such as wolves or coyotes, explains wildlife biologist Rachael Urbanek at the University of North Carolina Wilmington. Still, the core question is the same: Is there evidence that killing effectively manages populations? The answers differ case to case, she says.

And then there's the core ethical quandary: Even if lethal control can work, is it the right thing to do? What if you can only guarantee it will work for a few years? How do you value one animal over another? Those questions fuel a heated debate, which simmers ever hotter as public attitudes about animal welfare evolve. Values, as much as data, are likely to determine whether governments and communities abide lethal control as a policy.

Frontier Origins

Wiens had never fired a gun before training for this experiment. Killing any bird of prey ran counter to his ecology education before the study. "Every time I went out there to do it, it was extremely difficult," he says. But Wiens believes that to maintain biodiversity, lethal control has become "more and more necessary," particularly in the case of invasive species.

Others disagree. "I don't think you can find any research that does adequately demonstrate that lethal control works," says William Lynn, an ethicist in the Marsh Institute at Clark University in Massachusetts and the founder of PAN Works, an animal ethics think tank. The US Fish and Wildlife Service hired Lynn 15 years ago to lead a stakeholder group (which included conservation organizations and timber industry representatives) to discuss ethical concerns about the planned barred owl removal experiment in the Pacific Northwest (1, 2). Many participants said they valued the owls' lives and recoiled at the thought of routine killing.

The owl case is one of the most meticulously studied. Barred owls, native to eastern North America, have spread west over the last century (an expansion unintentionally facilitated by humans) and are now encroaching on the last western old-growth forests where threatened spotted owls roost. The hope is that by killing thousands of the encroachers, wildlife biologists can stabilize spotted owl populations.

The results of Wiens' experiment are promising. After removing about 3,000 barred owls over a six-year period, the USGS team found that spotted owl populations stabilized (3). The US Fish and Wildlife Service now plans to conduct a scaled-up 30-year cull of barred owls, starting this year, based largely on the results of the experiment. As of early March, a number of lawmakers from multiple states encouraged the Trump administration to scrap the plan, citing high costs and dubious success.

It's the latest salvo in a long history of efforts to kill in order to manage populations. The story of lethal control in the United States began on the Great Plains in the early 1800s, when European settlers decimated bison, elk, deer, and pronghorn populations, explains Brad Bergstrom, professor emeritus of vertebrate ecology at Valdosta State University in Georgia. Bergstrom chaired the Conservation Committee of the American Society of Mammalogists for nearly a decade. He authored a widely cited 2014 review on the history of lethal control in the United States, among other topical articles (4, 5).

What happened, Bergstrom says, is that starving wolves, bears, pumas, and other predators turned to cattle as prey. The US government responded with a program of shooting and trapping predators to protect livestock. Its modern incarnation is Wildlife Services, an agency within the US Department of Agriculture. "That's how it started, and we're still doing that," Bergstrom says.

Perception vs Reality

The Department of Wildlife Services is still the federal agency largely tasked with lethal control. In 2023, the agency killed 1,454,324 animals, according to their annual report (6), including 24,603 beavers, whose dams are blamed for flooding (7); 18,916 double-crested cormorant birds, whose eating habits are ostensibly pressuring fisheries (8); and 68,562 coyotes, which raise concerns about killing farm animals and pets, though there's little evidence that killing carnivores protects livestock (9).

"I think Wildlife Services has gotten a lot of negative media attention over many decades," Urbanek says. Much of it is undeserved, in her opinion. The agency's attitude certainly isn't "have at it-let's kill them all!" Wildlife Services studies nonlethal methods as well, she notes, whether directed at deer-car collisions or bird-airplane collisions.

Often, a government agency engages in lethal control-for instance, with coyotes-because of a public outcry, Urbanek says. "It's a social carrying capacity," she says. People start noticing more coyotes, eventually feel there are too many, and then complain to their local government, which can go to state agencies or Wildlife Services to intervene and neutralize the perceived threat. In Wilmington, where Urbanek lives, and where both human and coyote populations have grown in recent decades, "we don't want to get to that point," she says.

So, in 2023, she published survey results that gauged public attitudes toward the growing coyote population (10). The survey quizzed residents on their knowledge of normal coyote behavior and asked how the county should spend tax money-whether on coyote lethal control, public education about coyotes, or other measures. Only 11% of respondents said they'd had aggressive encounters with coyotes. Many of those stories came from wary people who saw a coyote nearby and felt threatened, Urbanek says. Most respondents supported spending tax dollars on public education over culling, except in cases of coyote attacks. Urbanek says the survey, by highlighting the role of education, is helping Wilmington get ahead of a widespread fearful response that might lead to lethal control.

Wilmington's parks and gardens have since begun a series of coyote education events. To keep humans and pets safe, Urbanek says she teaches hazing: "Getting an empty soda can, putting coins or rocks in it, taping it shut, and shaking it." Coyotes run off at the noise.

Silver Bullets

What does the science say? The answers and the caveats vary, case by case.

Consider the Blanding's turtle, a northeastern species that's endangered in some states due to habitat loss and the pet trade. "These guys are adorable and a really friendly turtle," Urbanek says. People tend to poach them as pets. In 2013, the Lake County Forest Preserve District was monitoring the turtles at two nature preserves on the Illinois-Wisconsin border and had two healthy populations left. The district was actively taking eggs from nests and hand-raising them, then releasing the young turtles back into the wild to give them a head start. But raccoons and other predators often discovered the nests and dug them up.

The district asked Urbanek's lab to see if culling raccoons before nesting season would help, by creating a window of time when the nests went undisturbed before the predators moved back in (11).

Her team trapped and killed 45 raccoons from the 2-square-kilometer study area in spring 2013, reducing raccoon population density by about 90%. Because raccoons can carry rabies, they couldn't legally be relocated. In the nesting season that followed, only one of seven, or 14%, of monitored Blanding's turtle nests was attacked and partially eaten.

The next year, though, the researchers repeated the experiment by culling 33 raccoons. This time, 9 of 15 turtle nests, or 60%, were attacked. Foxes, opossums, and skunks had likely moved in on the food source with the raccoons gone.

Urbanek's conclusion: Predator management, especially for threatened species, "can help to some degree"-after all, there was a boost for the Blanding's turtle nests in 2013. But in general, the two-year study showed that "predator management is not the panacea," she says. Killing the raccoons didn't save the turtles long-term.

Maybe if the team had killed foxes, skunks, opossums, and raccoons every year, they'd have seen a lasting impact. Then again, maybe not. There are communities on North Carolina's barrier islands that hire trappers to take foxes, raccoons, and coyotes, in hopes of helping endangered sea turtle nests. In those cases, Urbanek says, predators "move back quickly, even across the water."

Borne on Brown Wings

But it's the case of the barred and spotted owls that's received the most public attention of late-and spurred the most vocal controversy.

In this tale of two owls, the barred is larger, territorially competitive, and better at living alongside people. The northern spotted owl, by contrast, only lives in the old-growth forests of the Pacific Northwest and northern California, roosting in the cracked trunks of old conifers. The northern spotted owl has been a fiercely beloved mascot of the Northwest since 1990, when its listing as a threatened species under the Endangered Species Act gave teeth to forest protection efforts. These two owls have been on a collision course since around 1900, Wiens says, when European settlers planted trees on the Great Plains. Barred owls probably used those trees to hopscotch their way west from their native eastern forests. Since the 1960s, they've arrived in the Northwest, where they're outcompeting the spotted owls for nesting hollows and food.

In response, the US Fish and Wildlife Service developed the removal experiment, killing some 3,100 barred owls over six years in areas of Oregon, Washington, and Northern California, to test if their removal would slow, stop, or reverse spotted owl declines. It did seem to help. Spotted owl numbers stopped crashing at the treatment sites-though, notably, their populations didn't grow either. Populations leveled out at a 0% rate of change. In control areas, spotted owls declined by an average of 12% per year. At one control site, there was a single owl left by the end of the study (3). Since those results were published in 2021, Fish and Wildlife has unveiled a strategy of more widespread barred owl killing to be deployed, up to the next 30 years, across Oregon, Washington, and California.

Although Wiens thinks the plan is necessary to save the spotted owl, he also sees potential issues. It's been five years since his experiment, and at a decline rate of 12% annually, that leaves few spotted owls to save in places that already had small populations, such as Washington and northern Oregon. The larger spotted owl populations in Northern California and southern Oregon have been impacted heavily by barred owls recently, in the last 5-10 years, and culls should be effective there, he says.

Without implementing the strategy, and conserving old growth forest, Wiens says we'll eventually see extinction of the northern spotted owl. But barred owls have wider impacts on other species as well. He found the bones of smaller pygmy and screech owls in the stomachs of barred owls during the experiment. And many of these smaller native owls are also competing with barred owls for the same small mammal prey. It's never been just about northern spotted owls, he says; it requires "a more holistic view."

Bergstrom calls the owl research "intricate" and "well-designed" and says those attributes make it "the exception, not the rule" for cases of predator lethal control. But he would argue that a scaled-up cull of barred owls only treats a symptom of habitat loss, not the habitat loss itself. "Extreme habitat specialists are in trouble everywhere," he says, "and the only long-term solution is to restore their habitat."

Even if thousands of barred owls are shot, that won't suddenly free spotted owls to expand beyond the tiny islands of habitat left to them. "I hate to say it, but I think the spotted owl is doomed," Bergstrom says. "Because even if barred owl removal works, is it really going to be funded forever? Or for as long as it takes for the old-growth forests to grow back?"

Toward Value and Virtue

Some argue that lethal control has become so polarizing because it's really more of a values debate than a scientific one. When is it OK to take the life of an animal, especially an intelligent one? "While there are scientific questions in play...there is a more deep-seated controversy that stems from value differences," which often go unacknowledged or underacknowledged, says interdisciplinary scientist Jeremy Bruskotter at The Ohio State University in Columbus. Questions about lethal control's effectiveness are rarely separate from the more emotional quandary: Even if it works, "should we do it?" he says.

Bruskotter coauthored several recent studies suggesting that opinions on lethal control-and how we value wildlife in general-are changing. In a survey of 43,949 people across all 50 states, published in a series of papers (12-14), Bruskotter posed 19 questions about ideal relationships with wildlife and dozens of other questions to gauge public perceptions of wildlife-related issues.

For each question, participants read a statement, such as "the needs of humans should take priority over fish and wildlife protection," and then indicated their alignment on a scale from "strongly agree" to "strongly disagree."

Comparing those results to similar questions from earlier studies, as far back as 2004 and in 19 western states, attitudes had significantly shifted toward viewing animals as "morally relevant," Bruskotter says, meaning deserving of care and compassion, as opposed to just a means to human ends. "People are demanding good answers for why animals should be killed," he says. However, the results were not uniform across the West. The values shift was most pronounced in Utah, Nevada, and California, where more sympathetic views of animals had spread since 2004. But in the same analysis, more traditional views of animals as resources had expanded in 2 of the 19 states, Wyoming and North Dakota. Increasing disparities in public values state to state suggest one reason why disagreements over lethal control are getting more polarizing.

"Science is the surrogate for what is actually a values debate," Bruskotter says. The relationships people wanted with wildlife even 10 years ago aren't the relationships they say they want today.

"In the majority of cases, lethal control doesn't do what people expect and want," says ecologist Adrian Treves at the University of Wisconsin-Madison. The field has become so polarized that researchers are entrenched in camps, he adds. "People have forgotten the lesson that when those scientific debates get so hot, that's when we need more and better data," Treves says.

There are at least ways to make killing more humane. In the case of the owls, Wiens' study included protocols to take only clear shots at close range, using a special type of quiet gun barrel. "Usually, it was one shot, and that's it, so it was very quick," he says. The culled owls were physically intact and became museum specimens for future studies.

Ultimately, lethal control is a response to dilemmas humans have created-poaching, habitat destruction, the spread of invasive species. "In our history as humans, we've moved animals and plants around to hunt them and eat them, or because they look pretty," Urbanek says. "We are still playing that role and trying to fix that."


Amy McDermott wrote this article for the Proceedings of the National Academy of Sciences.


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