"Movement of pygmy owls from Mexico to Arizona may be necessary for the persistence of the Arizona population," Flesch pointed out.
The security wall could have a bigger impact on the movement of bighorn sheep, which range widely among the hilly terrain. The scientists' study estimated that at least nine populations of sheep in northwestern Sonora, Mexico, are linked genetically with animals in neighboring Arizona and an interruption of that connectivity could threaten populations on both sides of the fence.
An impermeable barrier would isolate sheep populations and potentially reduce their genetic diversity, but the scientists say slight adaptations in the design of the fence could improve the animals' potential for connectivity while maintaining the desired security goals along the border.
"The key is to have gaps in the fence that are sufficient to allow passage of animals, while at the same time meeting security needs," Epps said. "A 'virtual' fence could be an alternative to a solid wall in some places, especially in steep terrain that is ideally suited for bighorn sheep. The use of cameras, radar, satellite monitoring and vehicle barriers could provide security and be great alternatives for wildlife."
Though their study focused on pygmy owls and bighorn sheep, the scientists also recognized other animals that could be affected by the security wall. Flesch said black bears, jaguars, pronghorn antelope, desert tortoises and ground-dwelling birds including wild turkeys and quail could be affected by restricted movement.
"Ultimately, the effects of the fence will vary among species," Flesch said. "Populations that are relegated to patches of habitat that are small and naturally fragmented are most likely to be affected by the fence, especially species that have low rates of movement among habitat patches."
Epps, who is an assistant professor in
|Contact: Clinton Epps|
Oregon State University