SHERIDAN – There is no place like home for the northern mule deer of the Bighorn Mountains.
Almost two years after the first of 130 mule deer collared for a movement study in the Bighorn Mountains, researchers were surprised at how little movement there was, according to Tim Thomas, a wildlife biologist at the Bighorn. Sheridan area in Wyoming Game and Fish Department. .
There has been a larger than expected segment of the herd that spends year round along the Bighorn foothills at lower elevations, Thomas said. Many deer on the east side of the Bighorns have been found to be residents rather than migrants.
Additionally, wildlife managers previously expected a fair distribution of deer moving to the eastern and western sides of the mountain during the winter, Thomas said. However, the majority of ring-necked deer have moved to the west side of the Bighorns during the winter season.
This data, along with other information gathered during the movement study, will help wildlife managers better understand the segment of the deer herd that spends the summer on the mountain. The study was initiated because of concerns about the mule deer population levels in the mountain. The objectives of the project are to identify the movements of the mule deer; assess seasonal range and habitat use; identify opportunities for habitat improvement and conservation; and documenting birth and death rates, Thomas said.
While movement is the primary focus of the study, it’s not the only information researchers are collecting on collared deer.
If an animal’s GPS collar does not register movement for several hours, indicating that the animal may have died, game and fish biologists receive an email notification. Biologists then travel to the most recent site to search for the carcass, retrieve the collar and attempt to identify the cause of death. Biologists may perform an autopsy in the field to try to determine the cause of death.
Another goal of the study is to learn how and when mule deer populations use areas treated for invasive plant species such as cheatgrass, ventnata, and medusahead.
This information could potentially inform future invasive species treatment projects in the Bighorns, Thomas said.
The collars were first deployed in March 2020, followed by additional collars in August and December 2020 and in February and December 2021. Game and Fish plans to deploy 35 additional collars in March 2022 thanks to recent funding from the Bureau of Land Management.
These new collars should provide valuable data on the youngest members of the herd, said Carrie Kyle, a University of Wyoming graduate student working on the project.
“In March, we will try to capture the fawns from our collared does, with the goal of documenting 35 doe / fawn pairs,” Kyle said. “With these new captures, we aim to document how the dam strategy and year-over-year conditions of the calves affect their migratory decisions throughout their lifetimes.”
The data researchers are currently receiving is minimal, Thomas said. During the course of the study, biologists receive one or two location updates per deer per day, allowing for regular tracking of movements throughout the year. However, the collars do record and store the GPS positions of each deer every two hours. These detailed movement data will be accessible at the end of the study when downloading from the on-board computer of each collar.
“Data analysis will not begin in depth until the summer of 2023, when the first collars deployed in 2020 will begin to automatically release from the animals,” Thomas said. “… Once the data analysis is complete, the information will be used to inform future deer management decisions for the North Bighorn Mule deer herd.” “