UC Berkeley researchers find fences in Wyoming impact deer migration

Image of deer
marksbunker/Creative Commons
According to UC Berkeley doctoral candidate Wenjing Xu, deer grazing grasslands promotes a “very healthy" growth cycle in grasses, which can remove more carbon from the atmosphere than forests. Grazers that are trapped in a pasture by an impenetrable barrier – such as a fence – can overgraze, ultimately resulting in fragmented landscapes and negative impacts on climate change. (Photo by marksbunker.)

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UC Berkeley doctoral candidate Wenjing Xu published an article in the British Ecological Society Jan. 6, which analyzed how fences impacted mule and pronghorn deer migratory patterns in Wyoming.

As a part of her dissertation for UC Berkeley’s department of environmental science, policy and management, Xu observed how fences impacted mule and pronghorn deer migratory behavior. Mule deer east of Wyoming’s Rocky Mountains in the winter migrate westward in the summer to reach fresher, greener pastures atop the mountain range, according to Xu.

“For pronghorn, it’s quite mysterious because their migration behavior is so flexible and also in such a gradient that we don’t know,” Xu said. “Sometimes they stay in the same winter area … maybe some individuals are worse at crossing fences, so they’re more restricted, and some individuals are better at doing that.”

Mule and pronghorn deer can cross, walk along or get trapped by fences while migrating, according to Xu. She added that while she and her colleagues found trapping behavior, they still do not understand the nuance of why these animals are trapped they could be physically impeded by the fence, or they may actively choose to remain in one pasture.

Since this study only described spatial behavior, Xu said scientists have to do further research to understand the ecological consequences of these migratory behaviors.

Grazing a grassland promotes a “very healthy” growth cycle in grasses when animals are allowed to move on to give the grass time to regrow, according to Xu. Healthy grasslands can remove more carbon from the atmosphere than forests.

Grazers that are trapped in a pasture by an impenetrable barrier can overgraze. As a result, a fragmented landscape is created and can cause a negative impact on climate change, Xu added.

Xu and her colleagues decided to study ungulate, a group of animals that include deer and elk, migration because they are mostly terrestrial and travel large distances. Xu added that she and her colleagues specifically studied mule and pronghorn deer because they both live in the same part of Wyoming and happen to cover the same migratory area. This allowed them to directly compare each species’ responses to the same fences, according to Xu.

“The new, emerging field of fence ecology is super exciting and we are trying to promote it to be more formalized as a subdiscipline for ecology,” Xu said.

About a year ago, Xu contacted Valentine Herrmann, a research assistant at the Smithsonian Conservation Biology Institute, asking to develop the code Xu and her colleagues used to analyze fence and animal locations. Herrmann said her role was to make the code more applicable to further research as it was originally targeted to Xu’s data.

The code is now openly available on GitHub, a code and data platform open to the public, where researchers can use the code on their own data, according to Herrmann. She added that she will stay with the code to fix any potential glitches or methodological errors for any future users.

“I was super excited to be involved in this paper,” Herrmann said. “I’m super happy that it’s getting so much attention because I think it deserves it.”

Eric Rogers is the lead research and ideas reporter. Contact him at [email protected] and follow him on Twitter at @eric_rogers_dc.