Extending the sample across the border, a University of Arizona team has established a high degree of connectivity between Arizona’s and Mexico’s black bears. Although the populations are closely related at present, Melanie Culver, the USGS geneticist who directed the work, points out that bears live a relatively long time, so the distinctions between the groups may show up in future generations. “The wall hasn’t been there long enough to have demonstrated it yet,” Culver argues. “There are bears alive that predate the wall, and they’ve had an opportunity to move from one side of the border to the other. It’s not a complete barrier yet.”
“Bears in Sonora are endangered,” emphasizes Atwood, who has since moved to Alaska to work on polar bears. “It’s highly probable that the fence is restricting gene flow where the fence is not permeable.” Atwood concedes that the species is at the extreme margin of its range in Mexico, but if bears there are cut off and disappear, “it will be a loss, and you hate to see a loss of range.”
To mitigate the impacts of the fence and Border Patrol activity, the Department of Homeland Security has committed to spend $50 million for environmental enhancement projects and field studies, but few projects have materialized. In Cabeza Prieta, DHS has paid for water catchments for pronghorn — shallow troughs that capture rainwater for drinking — and has also contributed funds to the captive breeding program. Species along the border are, in effect, competing with one another for DHS funding, and the larger animals tend to do better than smaller ones in the competition. The jaguar, for example, which is popular with the public, has garnered more than $2 million worth of “mitigation money.” At least 10 studies of the big cat are underway.
A solitary hunter with skull-crushing jaws, the jaguar is the largest feline predator in the New World. Hounded for centuries, this endangered species no longer breeds in the southwestern United States. Indeed, the nearest healthy breeding population of jaguars is located 120 miles south of the line in Sonora. Yet because roaming males are occasionally sighted in Arizona, University of Arizona scientists, led by Culver, got $800,000 to deploy motion-sensitive cameras in areas where the cats were most likely to venture across. Before biologists even think about managing a population, as with the pronghorn, a rough inventory must be taken. Meanwhile, responding to pressure from environmental groups, the FWS has listed some 760,000 acres of Arizona and New Mexico as critical habitat for the jaguar.
That millions of dollars are being spent on a species without a foothold in the U.S. bothers connectivity specialists such as Aaron Flesch. Flesch, a biologist at the School of Natural Resources and the Environment at the University of Arizona, has studied ferruginous pygmy owls, whose short, low flights might be crimped by high border walls. He would like to see more species in the mix being studied. “Not hummingbirds,” he explains. “They can fly over the fence. But I’d select [species] on the basis of how fragmented their habitats are and their capacity for movement across the border.”
Like others entering the field, Flesch has tried to fit his past research on animal movement behavior into the new conditions at the border. When he and five colleagues analyzed the harmful effects of the border fence on pygmy owls, bighorn sheep and other species in a 2010 paper, they dealt with hypotheticals. The real work simply didn’t start soon enough. “The fence gained its political traction quickly — with no environmental assessments,” says bear biologist Atwood. “We had no baseline. Everyone was caught flat-footed.”