Hands-on Sheep Making the Difference: How capturing more than 760 wild sheep is securing a brighter future for this iconic species.

In Fiscal Year 2023-24, Wild Sheep Foundation (WSF), through its Grant-In-Aid program, supported the capture, handling, sampling, and, for many, GPS collaring of more than 760 wild sheep across nine separate projects in North America. Why would WSF invest so much into this aspect of wild sheep conservation?

The answers are within each of these unique and important undertakings.

Spatsizi Provincial Park, BC

From a conservation perspective, Stone's sheep are perhaps the least studied of the four North American wild sheep (FNAWS). Gaps in knowledge and data, as well as current population estimates, inspired this WSF multi-year project that resulted in the capture and collaring of 40 sheep in this famous, historic part of British Columbia. This project also allows a deep look at Stone's sheep's seasonal range and movement within Spatsizi Provincial Park, along with pathogen/disease surveillance. It also created an opportunity to gauge how human presence and hunter behavior possibly influence Stone’s sheep movements. 


 

Franklin Mtns State Park, TX

The Franklin Mountains north of El Paso provide excellent habitat for desert bighorn sheep, which were extirpated more than 100 years ago. Since 2019, Texas desert bighorn sheep have declined in many mountain ranges, due to respiratory pneumonia from Mycoplasma ovipneumoniae (Movi) and other bacteria, possibly linked to aoudads and domestic sheep/goats. The Franklin Mountains are free of these invasive exotics and domestic livestock. Once established, this Franklin Mountains herd will become the second disease-free herd in Texas, along with Elephant Mountain Wildlife Management Area (WMA); these source populations are vital to restoring and expanding desert bighorns in Texas. 


Completion of two guzzlers in Franklin Mountains State Park in mid-March 2024 helped pave the way for up to 80 desert bighorns that will be captured at Elephant Mountain WMA near Alpine, and released in FMSP. These sheep will be screened for pathogens, have their fitness/health assessed, fitted with GPS radio-collars, and released into Franklin Mountains State Park in fall 2024, creating a landscape-level legacy project to ensure Texas' herd viability into the future. This also aids Elephant Mountain WMA by helping its population not exceed carrying capacity.
 
Aerial and ground surveys, large predator inventory, and possible future water development will continue for several years as a restored FMSP herd gains a foothold in its newly re-established range. 
 

Tri-State (ID/OR/WA)

This ongoing multi-jurisdictional adaptive management project continues investigating the use of test-and-remove to clear Movi from at least 7 herds. That means captured bighorns found with the deadly pathogen are euthanized to prevent or minimize spread across the landscape.
 
This involves focused testing of groups of sheep with the highest likelihood of being infected, as well as continuing to monitor populations and subpopulations where chronic carriers have been removed; “control” populations where no removals have been conducted will provide comparative data to the test-and-remove herds.
 

All capture, sampling, mortality, and survey data will be entered into a shared database to estimate metrics associated with infection and transmission within and across populations, to help focus future testing and evaluate results of past removals.

 

Fraser River, BC

In year six of test-and-remove treatments that have produced promising lamb recruitment results in Canada's largest California bighorn metapopulation, the goal is to clear Movi and pave the way for full herd recovery.
 
This means following test-and-remove methods developed over the first five years of this project and applying this disease recovery method to other bighorn sheep herds. The goal is to capture 100 percent of the ewes in the area, use a Biomeme (field) PCR to determine Movi status, and aid managers with their decisions to remove all positive individuals. Healthy ewes mean healthy lambs, which is key to long-term population stability.
 

ION Partnership (ID/OR/NV)

This partnership among three states spans a key region for the California bighorn subspecies. It involves Movi test-and-remove efforts, population surveys and analysis, and identifying chronic disease carriers.
 
When large nursery groups of ewes and lambs are formed every spring, it only takes one chronic-shedding ewe to infect other ewes and lambs. This has drastically driven populations down to a fraction of their former numbers.
 
There are no outward signs to identify a chronic shedder; therefore, most adults may need to be captured and tested to find and remove the few animals contributing to the lambs' chronically high mortality.
 
All captured and released animals will be collared using a combination of VHS and GPS collars to cut costs, and they will be individually marked to facilitate possible recapture and lamb recruitment. After the initial year of testing, the focus will be on subgroups identified as having the greatest Movi prevalence. Positive individuals will be re-tested the next year to distinguish chronic from intermittent carriers, with testing ongoing for at least three years. Removals will occur in years two and/or three, following positive tests over two years.
 

Whiskey Mountain, WY

Following a large, all-age die-off caused by pneumonia during winter of 1990/1991, this Rocky Mountain bighorn sheep herd has experienced chronically low lamb production, leading to continued population decline.
 
Based on research conducted by the University of Wyoming (UW), the presence and prevalence rate (31%) of Movi in both adult and juvenile bighorn sheep throughout the Whiskey Mountain herd has contributed to poor lamb survival. 
 
This project will attempt to capture all available adult ewes via aerial net-gunning, a drop net, and ground darting in Hunt Areas 9 and 10 when sheep are on their respective winter ranges. Rams will be tested opportunistically via drop net, but the male cohort will not be targeted for testing and removal like ewes in the project. The decision to focus only on adult ewes is based on feasibility of capturing rams and test-and-remove research in both Hells Canyon, ID and Fraser River, BC where those herds have shown improvements in lamb recruitment, without removing any rams.
 
All captured animals will be sampled and marked with GPS collars, with two ear tags attached to visibly identify sheep, if removal is deemed necessary. Collars will be attached with a release mechanism that will be triggered after two years, allowing retrieval and possible re-deployment of those collars.
 
During year one of captures, Movi will be tested using a "field-based" PCR setup, and results will be validated with PCR testing in a lab setting.
 

This will increase knowledge and understanding of any differences in detecting Movi using a slightly different approach based on comparisons of field vs. lab results. Assuming the field test is validated, future testing will be done using a "field" PCR setup that will allow managers to hold captured sheep for a short duration, and either remove or release them. In the interim, all healthy bighorn sheep will be released with a GPS collar, and lab-confirmed positives will be subsequently removed as quickly as possible before lambing season. Lethal removal may occur through helicopter capture and/or personnel on the ground.

 
Identified carriers that reside in the wilderness will be removed from the ground. While the difficulties in capturing bighorn sheep at high elevations and in wilderness settings are recognized, it is prudent to test every ewe that can be captured. 
 

Wildcat Hills, NE

The Nebraska Game and Park's Commission (NGPC) has a goal of establishing a self-sustaining, free-ranging population of Rocky Mountain bighorn sheep in all areas of suitable habitat in the state on the eastern fringe of bighorn range.
 

With this project, the agency is considering an internal translocation of bighorn sheep within the Wildcat Hills region of the southern panhandle. This would involve capturing 10-20 ewes and transplanting them into an area already occupied by a small herd of rams; several years have passed without females making this same expansion to previously-unoccupied habitat.

 
This will also be the second year of evaluation of three Movi testing methods, including the “gold-standard” Washington Animal Disease Diagnostic Laboratory (WADDL), Biomeme Portable PCR Unit, and Working Dogs 4 Conservation (WD4C). WD4C continues with research across the country utilizing working dogs to help with disease detection.
 


Bighorn sheep will be captured via a contracted, helicopter net-gun crew and transported to a processing site to be evaluated, sampled, and isolated in trailers, pending testing results. Radio-collars will be deployed on uncollared sheep, while existing radio-collared sheep will be re-tested. 
 
In the northern panhandle region, 5-10 bighorn sheep would be captured for further evaluation and testing for Movi or other pathogens. All captured bighorn sheep in this region would be processed, collared (if needed), and released on-site, and would not be part of any translocation.
 

Chronic Carriers, WY

The entrance of epizootic pneumonia to bighorn sheep populations muddles the already complicated processes underlying population dynamics and is often the culprit for massive crashes of sheep populations, followed by chronically low survival of young. 
 
It has been proposed that pneumonia may be maintained in populations by a few individuals that are chronic carriers and with their removal, could alleviate the prevalence of Movi.  This study would involve the capture of 70 bighorn sheep.
 

This method has proven impactful in recent years. For example, in two small populations of bighorn sheep in western South Dakota, Garwood et al. (2020) implemented a test-and-remove program in one herd and left the other as a control; two chronic carriers were identified in each herd. Upon removal of the two chronic carriers from the treatment herd, the mortality loss for lambs was reduced by 72 percent compared with the control herd. Also, there was a 41 percent reduction in adult mortality. Similarly, in Oregon, an opportunistic observation of loss of a single Movi positive individual from a population improved juvenile survival (Spaan et al. 2021). 

 
Consequences of pneumonia pathogens within populations, however, are not consistent across populations or even across time. Therefore, die-offs are likely dependent upon certain ecological or environmental conditions. Understanding these interactions could yield management alternatives to help reduce the frequency of large-scale mortality and dampen fluctuations in abundance. 
 

Stone's Sheep/Omineca, BC

The goal of this project is to investigate the influence of range condition on body condition in Stone's sheep in the Finlay-Russel ranges. The first step is quantifying forage quality, quantity, and availability on summer and winter ranges. These range conditions will then be matched to individual-based sheep movements using GPS tracking on 22 adult female sheep. 

 
This will be followed up with body-fat measurements twice a year-including one in late fall when animals are at peak body condition, and then again in late winter when their energetic reserves are depleted. 
 
Animals will be captured using helicopter net-gunning in accordance with provincial and university animal care protocols. This research would investigate limiting factors for Stone's sheep in the interior snowbelt, at the southern edge of their distribution, where range constraints may vary from other well-studied herds in relatively drier areas. This information, when paired with fine-scale body condition data, will lead to an improved understanding of the role of seasonal nutrition and its potential to act as a limiting factor for Stone's sheep. 
 
This research will provide a mechanistic link between plants and wildlife populations, with implications for range restoration efforts where seasonal range quality or body condition is limiting. Providing meaningful habitat management recommendations in turn would increase the viability and conservation of an ecologically unique and culturally significant species that exist almost exclusively in British Columbia.
 
Be sure to check out more detailed reports on these projects in the Conservation Impact section of our website.
 

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By Kevin Hurley, WSF Vice-President for Conservation

Photos provided by Silverline Films (Header, Nevada - ION Partnership), Gray N. Thorton (Spatsizi), Lone Pine Media (Texas), Justin Haag (Nebraska), Landon Birch (Omineca)