Arizona’s border wall will include openings too small for many animals

New border wall passages the size of small doggy doors, 50 in total, are unlikely to mitigate the wall’s negative impact on wildlife, experts say.

Photograph by Krista Schlyer, iLCP
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The border wall cuts across the foothills of Arizona’s Huachuca Mountains, home to a range of species. It’s one of the only places in the United States that four wild cats have been sighted—mountain lions, bobcats, ocelots, and jaguars—which, like most large animals, will be impeded by the wall.

Photograph by Krista Schlyer, iLCP

Customs and Border Protection will soon finish installing 50 wildlife passages across 63 miles of recently-completed border wall in southern Arizona in an attempt to allow more small animals to move across the border. The openings, which some have likened to “doggy doors,” are flush with the ground and the dimensions of a standard sheet of paper—eight and a half inches wide and 11 inches tall.

The agency says the openings will make it easier for small animals to get through the wall, and that it plans to install more in the future. But scientists and environmentalists tell National Geographic that these openings are too small and too far apart to have a significant impact.

Nearly 400 miles of border wall have been completed in the last two years, mostly in California, Arizona, and New Mexico. This fencing, most of it 30 feet tall and made of bollard-style steel beams, has created an impenetrable boundary for wildlife, including mountain lions, bighorn sheep, deer, and many other species.

“This has got to be an obscene joke,” says Laiken Jordahl, a conservationist with the environmental group Center for Biological Diversity. “Fifty of these tiny openings along the entire Arizona border?”

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After traveling the Arizona-Mexico border looking for a place to cross, these javelinas gave up and turned back north. This stretch of wall bisects Arizona’s San Pedro River corridor, one of the last free-flowing rivers in the state and a haven for wildlife traveling north and south.

In response to this criticism, Customs and Border Protection (CBP) spokesperson Matthew Dyman says that the agency worked closely with the National Park Service and other federal agencies to pick the best placements for the passages, relying on existing data about the distribution of species and migration routes.

“Several species of rabbit, fox, small desert tortoise, skunk, raccoon, coatimundi, opossum, coyote, gila monster...badger, ringtail, and weasel could potentially use the passages if they do not already go through the fence,” which has four-inch gaps between its beams, Dyman says.

Left out

The openings will not help larger animals whose habitats straddle the border. Endangered Sonoran pronghorn antelope, for example, used to move more freely between Mexico and the United States—but now the wall ends any hope of movement through their range in Organ Pipe Cactus National Monument and the Cabeza Prieta National Wildlife Refuge. It’s a major threat to their existence, Jordahl says, because it will cut off gene flow among herds and their ability to forage.

Jaguars, an endangered species whose northern range extends into Arizona, also cannot pass through the small openings. By January the wall is on pace to block access to the majority of jaguars’ critical habitat in the state, says Myles Traphagen, a conservation scientist with Wildlands Network, a nonpartisan environmental group dedicated to preserving wildlife corridors.

More common species such as deer, coyotes, and black bears also will not be able to fit through the passages. CBP’s Dyman says that those and other large animals will still be able to pass through some valleys where the wall is outfitted with flood gates. Those gates will mostly be open during the monsoon season, from June to September, so the wall isn’t overwhelmed by flash floods. At those times, bigger creatures can pass through, he says.

Traphagen contends that creating just a few small openings in the border wall could create unforeseen problems. Allowing only diminutive animals to pass through could disrupt the balance of larger predators and their smaller prey, he says. It could also allow baby animals, such as javelinas and potentially bobcats, to get separated from their parents which are too big to make it through such openings.

Will animals use them?

With fewer than one passage being incorporated per mile of fence, conservationists worry that animals will have a hard time finding them. And even if they did, access roads and patrol cars along the wall, as well as bright lights installed in certain areas, may dissuade animals from using the openings, says Louise Misztal, executive director of the Sky Island Alliance, a nonpartisan environmental group in Arizona.

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The new openings are the size of a sheet of paper—eight and a half inches wide and 11 inches tall.

“The point is not so much whether any animals could use them; it’s more a question of whether any animals would,” says Randy Serraglio, a wild cat specialist and conservationist with the Center for Biological Diversity.

It can take months and years of monitoring and adjustments to create wildlife passages that animals will use and benefit from, says Andrew Jakes, a wildlife biologist with the National Wildlife Federation who has studied pronghorns’ use of fence openings in Montana. Nonetheless, CBP has no current plans to monitor them, Dyman says.

In Texas, CBP installed wildlife openings in some parts of the border wall prior to 2017 to allow ocelots and other animals to pass through, but there has been no monitoring of those either, according to Serraglio.

“There is no proof that wildlife in south Texas are using the ones installed there, let alone that there is any conservation benefit,” he says.

Monitoring the effectiveness of mitigation strategies such as wildlife passages is recommended or mandated by various laws, such as the National Environmental Policy Act. But under the 2005 Real ID Act, the acting secretary of the Department of Homeland Security Chad Wolf has waived scores of laws to build and modify the wall.

Traphagen, who has studied cross-border migration and habitat connectivity in Arizona and New Mexico, was asked by U.S. Fish and Wildlife Service researchers to assist in negotiations with CBP about where to place the passages. He says the process was rushed by CBP, lacking in “good faith,” and seemed designed to create “a veneer of compliance and stewardship.”

Dyman didn’t respond directly to that characterization. He reiterated that the agency held meetings with subject matter experts from federal agencies to pick ideal spots for the openings, and then met again with some of them on the ground “to refine each location to maximize the potential use of these openings by small animals.”

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Bison are one of the many diverse animals found in southern Arizona and northern Mexico that cannot surpass the border wall.

One of the most sensitive landscapes the border wall cuts through is Arizona’s Sky Islands, mountain biomes that have some of the highest levels of biodiversity in the country. CBP has placed some of the 50 openings in these areas, but conservationists worry it’s not enough. These mountainous areas serve as corridors for animals and had been mostly spared from wall construction—until early 2020, when President Trump began to aggressively ramp up border wall construction through wilderness areas. (Read more: Border wall construction expands, despite pandemic, imperiling jaguars and other animals.)

Aaron Flesch, a researcher at the University of Arizona who’s studied the impact of walls on animal movement, is more optimistic than the other researchers. He says the passages are a “step in the right direction.”

But, he says, “It’s a tiny step.”