Unique Females with Cubs of the Year (FCOY)
Adult females are considered the most important segment of the grizzly population and consequently are a major focus of IGBSTs monitoring program. Efforts to document the distribution and abundance of females with cubs within the GYE began in 1973. During the past 10 years (2003-2012), IGBST has estimated an average of 50 unique females with cubs of the year in the GYE annually. When combined with other data, these counts serve as the basis for estimating total population size and determining whether annual mortality is sustainable. Sustainable mortality establishes the upper limit on the number of grizzly deaths that can occur yet still maintain a healthy population. As the US Fish and Wildlife Service evaluates de-listing the Yellowstone grizzly bears, information from these studies is used to evaluate trends in the bear populations and assess the long-term likelihood of a sustainable population.