News
Hart Mountain National Antelope Refuge (NAR) staff started their New Year with a successful capture of 23 adult California bighorn sheep with the support of Oregon Department of Fish and Wildlife (ODFW). Additional funding for sheep collars was provided by Wild Sheep Foundation.
Refuge Complex Wildlife Biologist Kim Haab stated, “We were able to get all 23 [GPS] collars deployed, which gives us a total of 35 collars [active] on air at Hart. This increased sample size is incredibly helpful for assessing adult survival and better understanding space/resource use of the herd.” Knowing where they travel and use the landscape helps to determine where they are using sustainable resources of food, water, and shelter to support their population growth.
When a sheep is captured, health biometrics are quickly taken, and a GPS collar is promptly placed around the sheep’s neck. Within 10-15 minutes, the sheep is provided a body condition score by its weight and rump fat measurements, and bio-samples of blood and fecal matter are collected to test for diseases before it is released with the collar. The staff works quickly and quietly to decrease the stress on the animal. The health of the animal is of the upmost importance, so they are also provided antioxidants like Selenium and vitamin E. Continuous monitoring occurs through the entire event.
This collared sheep study is done in compliance with the Hart Mountain NAR Bighorn Sheep Management Plan. The plan calls for collaring bighorn sheep to help study the bighorn sheep’s population and health. This is important as the last bighorn sheep in Oregon were extirpated in 1912 then first reestablished at the refuge with 20 bighorn sheep in 1954. As the population increased, the herd was later used to reestablish bighorn sheep in surrounding areas. However, the bighorn sheep population on the refuge declined by 67% over a four year period to a population of about 48 in 2020. That trend placed the population at risk of extirpation without management intervention and, as a result, a management plan was developed. Since implementation of the plan in 2022, the refuge bighorn sheep population has increased to a population of about 90 bighorn sheep.
In addition to bighorn sheep captures, the U.S. Fish and Wildlife Service has continued to improve
U.S. Fish & Wildlife Service bighorn sheep habitat through the removal of juniper trees, treating invasive weeds, and monitoring of springs. Both pronghorn and bighorn sheep benefit from the removal of junipers as the juniper trees reduce the availability and quality of forage, reduce the availability of water, and leave the bighorn sheep and other wildlife vulnerable to predation.
Scientific studies will continue with a special interest from the impact of the Warner Peak Fire, which occurred August 2024. During the next 3-5 years, this will be a good time to continue the study of the sheep herds and how the fire affects their habitat and movement.
Hart Mountain NAR’s Manager, Josh Loew, stated, “It always amazes me to see the incredible work that goes into these critical conservation efforts. The collaring of these sheep took immense amounts of coordination and the staff at the Refuge and ODFW did a flawless job in making this happen. I am grateful to have been involved and thankful for each and every person that helped out.”
Updated January 15, 2025