GPS monitoring, simulations present optimum places to assist desert bighorn sheep cross highways

Three bighorn sheep. Photo credit: Regina Abella, California Department of Fish and Wildlife.

Desert bighorn sheep, whose southern California range is intersected by freeways, may one day benefit from models from Oregon State University to show where the animals are most likely to use flyovers to safely cross the freeways.

The research is important because it shows how GPS tracking data and computer simulations can be used to predict animal movements — information needed for optimal siting of crucial but expensive habitat connectivity improvement projects.

The results of the study, led by Christina Aiello, a research fellow at the OSU College of Agricultural Sciences, were published in Landscape Ecology.

“Our work is already impacting conservation and land management decisions,” Aiello said. “The study’s findings are central to discussions among California officials about improving connectivity for wildlife across barriers such as freeways and a proposed high-speed rail project from Southern California to Las Vegas. Government agencies and non-governmental organizations have expressed support for the construction of wildlife crossings at three key sites identified through our research.”

A collaboration also involving Clinton Epps, a professor at Oregon State College of Agricultural Sciences, and Paige Prentice, a graduate student at OSU, examined GPS data of collared animals from nine bighorn populations in the Mojave Desert.

The 20-million-acre desert includes Death Valley and Joshua Tree National Parks and Mojave National Preserve, as well as Interstate 15 and I-40. The middle divider of I-15 would hold the tracks of the planned 200-mile train, which would be separated from automobile traffic by a 6-foot concrete wall on either side of the tracks.

Aiello, Epps and Prentice teamed up with National Park Service scientists to analyze bighorn movements as a series of stepwise processes. This type of breakdown allowed the researchers to determine which landscape features the sheep would prefer to travel through and which they would prefer to avoid.

“The computer models we used are known as step-selection functions because they determine what habitat bighorns select when they take steps from place to place,” Aiello said. “There is no GPS data ahead of the freeway showing how Bighorn used to drive, so we use our models to simulate where Bighorn would go if those freeway barriers suddenly disappeared. However, freeways continue to restrict where Bighorn can travel, and they have existed for decades.”

The scientists ran simulations over a total of 8,200 years in the life of bighorn sheep – 200 one-year periods each for 41 individuals in landscapes with and without highways. The results of the simulations match well with what genetic data and road fatality numbers have suggested regarding movement corridors, the researchers say, and offer a more detailed look at how the sheep would benefit from a man-made obstacle-free environment.

“Barrier removal has increased accessible habitat for eight of the nine populations we studied,” Aiello said. “Our results can answer important ongoing land use and restoration questions, such as: B. where should we set up a deer trail where bighorn sheep would benefit and be used the most? Access habitat and interact with each other?”

This type of information, she added, is particularly important in desert habitats, which continue to see major development proposals related to solar power, transportation and urban expansion.

“There are limited resources in desert ecosystems, making movement and access to diverse habitats particularly important for wildlife survival,” Aiello said. “Our study provides insight into how bighorns could use this landscape if they were allowed to roam freely and choose their preferred habitat — this helps us know how much the species could benefit if we improve movement across highways.”

Neal Darby, Debra Hughson and Nathan Galloway of the National Park Service also took part in the investigation.

More information:
Movement models and simulations show highway impacts and mitigation opportunities for a metapopulation-distributed species, Landscape Ecology (2023).

Provided by Oregon State University

Citation: GPS tracking, simulations show optimal locations to help desert bighorn sheep cross highways (2023 January 31), retrieved January 31, 2023 from https://phys.org/news/2023-01-gps -tracking-simulations-optimal-bighorn. html

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