University of Idaho - I Banner
A student works at a computer


U of I's web-based retention and advising tool provides an efficient way to guide and support students on their road to graduation. Login to VandalStar.

Tracking Grazing Impacts on Sage Grouse Food

Biologists Learn That Livestock Increase Bug Numbers

They crawl or fly, buzzing, seemingly extraterrestrial, sometimes around a head and lights. And many animals eat them, making insects an important part of the diet of everything from snakes to greater sage grouse.

Every insect has a story going.

— Henry Trujillo, Entomology student

These characteristics and more make the creepy crawly interesting to entomologists Grace Overlie and her lab assistant Henry Trujillo.

The duo has been sorting insects — as well as arthropods such as scorpions and spiders — into their prospective families as they count, measure and identifying bugs captured in traps and nets, and bagged, as part of a years-long sage grouse study being conducted by University of Idaho.

Researchers wanted to know if spring cattle grazing reduces the number of insects available to young sage grouse, a food chicks rely upon in the first several weeks of their life.

Mugshot of a female student.
Master’s entomology student Grace Overlie, of Lowman, Idaho, collected data on the insects and arthropods that sage grouse eat, which were captured at traps as part of the grouse and grazing research project.

The study was part of a bigger project that investigated factors that may be linked to sage grouse population declines throughout the Rocky Mountain West. As part of the study, scientists investigated whether cattle grazing reduced the abundance of insects. Arthropods are a key food source for greater sage grouse chicks. Research shows that more than 90% of the diet of one- to four-week-old chicks is composed of arthropods.

Overlie, who is compiling data as part of her U of I master’s research project in entomology learned that more insects and arthropods are found in sage lands grazed by cattle.

“Spring grazing resulted in more abundant insects as well as more groups of insects,” Overlie said. “Insects found under the spring grazing treatment generally have a larger biomass, which could provide more food for sage-grouse.”

Mugshot of a male student.
Undergraduate entomology student Henry Trujillo, of Meridian, helped classify insects and arthropods that sage grouse eat.

Bugs for Breakfast

Two University of Idaho students are classifying, weighting, counting and measuring insects and arthropods caught in pitfall traps in southern Idaho as part of a 10-year grouse and grazing project that seeks to learn how cattle grazing effects sage grouse nesting.

Arthropods collected in pastures grazed by cattle weigh more, and there are more of them, she said. The findings will become part of the sage grouse research literature going forward, but the work continues as Overlie and Trujillo work in a lab in the basement of the College of Natural Resources.

“We have identified more than 270,000 specimens,” Overlie, who grew up in Lowman, Idaho, said. “We’re at sample 3,212 right now.”

Trujillo, U of I’s Entomology Club president, became interested in insects as member of the Meridian FFA chapter.

“Every insect has a story going,” he said. “There’s always some surprise the further you look at it.”

In Overlie’s lab, Trujillo uses a stereo microscope to get an up-close-and-personal look — right down to the number of spines on an insect’s legs, which distinguish it from another species — at the bugs that have been collected.

“The work I’m doing is going toward conservation. It’s going to make an impact,” he said. “Having that experience in undergraduate level is very valuable.”

Courtney Conway, Ph.D.

Professor of Wildlife Sciences, and Unit Leader of the Idaho Cooperative Fish & Wildlife Research Unit

CNR 103E


Email Courtney Conway

Department of Fish and Wildlife Sciences

View Full Profile

Article by Ralph Bartholdt, University Communications.

Photos by Rio Spiering, Visual Productions.

Video by Rio Spiering, Visual Productions.

Published in November, 2023.

Campus Locations

Physical Address:
Bruce M. Pitman Center
875 Perimeter Drive MS 4264
Moscow, ID 83844-4264

Phone: 208-885-6111

Fax: 208-885-9119