The Wild Sheep Society and project partners (BC Fish & Wildlife Branch, Wild Sheep Foundation, BC Sheep Separation Program, St’at’imc Nation, Arcadia Outfitting, Thompson Guides Association, BC Interior SCI, Clinton & District Outdoor Sportsman Association) are looking for dedicated volunteers to assist with summer lamb monitoring. Your involvement with the collection of observational data of lambs is an integral component of our collective efforts to recover bighorn sheep within the Fraser River. This information will allow us to evaluate whether treatment efforts to remove a bacteria called Mycoplasma ovipneumoniae (Movi) from a an important herd of bighorn sheep was effective in increasing lamb survival and recruitment.
Currently, Movi is considered the biggest threat to wild sheep in North America and has been detected in several sheep herds in BC. Once infection occurs, this disease is remarkably complex and can persist in populations for many years with no signs of recovery. Following initial exposure, some wild sheep die, at times up to 90% of herds may die, some sheep are able to resist the disease and develop strain-specific immunity and some sheep live with the disease and become chronic shedders of the bacteria through their nasal passages. The disease can persist until all individuals that chronically shed the disease naturally die out which can take a long time as new chronic shedders can continually enter the population (i.e., surviving lambs that become chronic shedders). The bacteria are passed between individuals by direct contact and the annual chain of transmission is from a chronically shedding ewes to their young lamb which then pass the bacteria to other lambs in the herd. Given the immune systems of lambs at that age are developing, often the bacteria causes high levels of lamb mortality within their first couple months of life and the result is persistently low lamb recruitment which prevents long-term recovery of the sheep population.
To break this chain of transmission from ewes to lambs, we conducted a test & remove project in an important nursery group on the west side of the Fraser River north of Lillooet (see Treatment zone on map below) in February and March 2020. We captured all females and young rams (47 in total) and tested them for the presence of Movi in their nasal passages. Sheep that were determined to be actively shedding Movi were euthanized from the band of sheep to break the chain of transmission of Movi from those ewes to their lambs in the upcoming summer. We expect lamb survival rates to increase post-treatment. To evaluate our success with this approach we are planning to compare lamb survival rates and timing of mortality over the summer and into the fall between the treated band of bighorn sheep and an adjacent non treated band (see Control zone on map), which is also infected with Movi and has been characterized by similar low rates of lamb survival in recent years.
This is where citizen science comes in! We hope to use volunteers to undertake sheep counts in a structured and periodic fashion through the upcoming summer to evaluate lamb numbers and survival. At minimum, we need 2 groups of 2 people per zone (8 in total for the Treatment and Control zones) to spend a day glassing, counting and classifying sheep on a set schedule. The schedule will depend on manpower but at minimum we are hoping to do counts monthly, starting the weekend of June 6-7, 2020 (4 counts: June 6-7, July 4-5, August 8-9, September 12-13). If manpower exists, we may consider doing these counts every two weeks starting on the above date (8 counts: June 6-7, 20-21; July 4-5, 18-19; August 8-9, 22-23; September 5-6, 12-13). We only require volunteers to spend a day at it on each count date but we will be encouraging folks to spend the night (e.g., camping) and repeating the count on the 2nd day as well to ensure we get good counts of sheep over the designated weekends and to make it a social event. We will provide observation field forms and instructions to ensure observations are collected in a consistent and structured manner. Experience counting and observing sheep is preferred.