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Animal migration routes are determined by both science and legislation

by Wyoming Livestock Roundup

Casper – “Animals migrate to make a better living off their landscape,” said Wyoming Fish and Game Department (WGFD) Cooperative Unit Leader Matt Kauffmann.

Kauffman, along with a panel of leading professionals, addressed residents of Casper and surrounding areas in regards to the importance of designated migration corridors at one of six statewide forums hosted by WGFD on Feb. 11. 

Why animals migrate 

“It’s not new information that animals migrate in the winter to avoid deep snow and harsh conditions,” Kauffman noted. 

“Smaller animals, such as pronghorn, begin their migration earlier due to a lighter tolerance for deep snow, whereas larger animals, such as moose and elk, can tolerate deeper snow and migrate later in the season,” according to Kauffman.

   He explained animals don’t necessarily beeline to their destination. Instead they take their time, sometimes up to two months, to migrate north or south for the winter. He estimated animals spend up to one-third of the year en route to their summer or winter habitats, making the route a habitat itself. 

Surfing the green wave

Kauffman described the slow migration of animals as “surfing the green wave.”

“Animals want to eat plants at the early stage of their growth, which is typically in the spring,” Kauffman said. “The early stages of growth, when plants are lower in fiber and higher in protein, is ideal because the plant is more easily digestible.”

“When animals time their migration correctly, they can expose themselves to spring-like, low-fiber plants for a longer period of time,” Kauffman explained. “Those who surf well have a higher percentage of body fat going into the winter and are more likely to survive.”

He went on to explain that animals who migrate a longer distance will also have higher stores of body fat in comparison to those who migrate shorter distances.

How do they know

Kauffman explained it was once a hotly debated question as to whether mammals innately know to migrate or if they learn the process and routes from their parents. 

“There was a study done with translocated Bighorn sheep,” Kauffman said. “The study found sheep didn’t migrate, which proves this is a learned behavior passed on to each generation.”

He explained due to the learned nature of migratory behavior, it can take anywhere from decades to centuries for a species to learn how to migrate. 

“When we lose a species in an area, all the knowledge is lost, too,” Kauffman commented. “This knowledge is accumulated over generations of learning to make the best of a landscape.” 

Charting migrations 

Due to advanced technology, animals can now be collared and tracked to determine their migration routes and assist managing agencies in determining designated migration corridors, according to WGFD Biologist Doug Brimeyer.

Brimeyer provided data for the Baggs, Platte Valley and Sublette mule deer migration corridors to attendees of the forum. 

Brimeyer noted Baggs had 118 individual mule deer collared and 298 seasonal migrations. Platte Valley featured 42 collared deer and 120 seasonal migrations, while Sublette had 131 collared deer and 319 seasonal migrations.

“We use the best technology we have available to us, as well as historic data, to determine migration routes and subsequently designate corridors,” said Brimeyer. 

In an effort to include the community, outreach efforts were made in areas affected by the migration corridors. 

“We host community meetings, send e-mails, post news releases and communicate with federal partners and landowners,” Brimeyer explained.  

Callie Hanson is the assistant editor of the Wyoming Livestock Roundup. Send comments on this article to

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