Three ewes were captured using nets fired from a helicopter. The sheep were transported to McCormick Park, where biologists from Idaho and Oregon monitored their health, took samples, and loaded them into a trailer for transport to South Dakota State University (SDSU). Representatives from the US Forest Service, Idaho Power Company, and the Idaho Chapter of the Wild Sheep Foundation also assisted in the operation.
The three ewes were the remnants of the Sheep Mountain herd, which once numbered over 80 individuals. The herd declined sharply following a pneumonia outbreak in 1999, and the last ram died in 2008. No lambs have survived for the past 5 years. A 2011 attempt by Oregon to supplement the population with a ram was unsuccessful because the ram died of pneumonia following contact with the remaining ewes.
The sheep will become part of an existing captive herd at SDSU involved in evaluating pneumonia and its impact on lamb survival. Bighorns will be tested to determine if they are chronic shedders of specific pathogens believed to be involved with the disease. Most bighorn ewes in populations with pneumonia problems are "nonshedders" that do not maintain infection and may be able to raise healthy lambs. The research at SDSU involves measuring health and survival of lambs born to these healthy "nonshedding" sheep in the absence of contact with "chronic shedders" and when they are commingled. This could lead to management options to improve lamb recruitment following pneumonia outbreaks.
Biologists hope results from the captive study can be used in the future to help develop options other than eliminating populations to recover bighorn sheep following pneumonia die-offs. Removal of these sheep now reduces the risk that bighorn sheep traveling from neighboring herds will come in contact with infected individuals.