As part of an ongoing study to understand the ecology of brucellosis and elk in the Bighorn Mountains, the Wyoming Game and Fish Department plans to capture and collar elk later this month. The capture would be cancelled if winter conditions in the area grow more severe and the capture would add too much stress on the elk.  

In mid-February, up to 52 elk will be captured using a helicopter net-gunning operation in the northern and southern Bighorn Mountains and on the lower Greybull River.  Capture crew members will take blood samples, fit each elk with a GPS tracking collar, which will take multiple locations per day, and then release the elk.

Bighorn Basin Brucellosis Habitat Biologist Eric Maichak said, “The study was initiated in 2015 in conjunction with the U.S. Animal Plant Health Inspection Service to better understand seasonal movements and brucellosis prevalence of elk in the Bighorn Mountains.  The project also aims to isolate and analyze genetic strains of the brucellosis bacteria to help determine how it may have spread to the Bighorn Mountains.”

Brucellosis, a disease caused by the bacteria Brucella abortus that causes elk to abort, is known to be widespread and common in elk in the Greater Yellowstone area. Elk and bison are the primary reservoirs of the disease, and it does not appear to limit their population size. Brucellosis can be spread from elk to other elk and to livestock.  

Since 2012, Game and Fish has documented nine seropositive elk outside of the Greater Yellowstone area, along the western flank of the Bighorn Mountains through testing hunter-harvested elk. Although prevalence remains very low, the consistent finding of seropositive elk in and around Elk Hunt Area 40 (on the northwest side of the Bighorns) is a concern to both wildlife and livestock managers and warrants further investigation.  “The information from this study will also be used to keep livestock producers informed regarding the presence and distribution of the disease,” Maichak said.  

Maichak explained that prevalence of the disease is the proportion of elk exposed to the bacteria in a given area.  “Animals that test seropositive for brucellosis do not necessarily carry the disease and may not abort.  However, they have been exposed to the bacteria at some time in their life, most likely from contact with aborted materials contaminated with the bacteria,” Maichak said.  

“Last year, 57 elk were captured, blood tested, and fitted with radio collars as a part of this effort,” Maichak said.  “This year, captures will occur again in the northern Bighorn Mountains and lower Greybull River to replace collars lost to mortality or failure, and to maintain consistent sample sizes.  Elk will also be captured in the southern Bighorn Mountains to address the recent hunter-harvest of a seropositive bull elk in Hunt Area 49 during the 2016 hunting season.”

Hunters have played a key role in brucellosis surveillance efforts by voluntarily collecting blood samples from harvested elk.  “Game and Fish sincerely thanks all hunters who submitted blood samples this past season.  These data are invaluable for helping Game and Fish, managers, and researchers monitor, understand management impacts and plan future research regarding brucellosis,” Maichak said.