Visibility Bias during Aerial Surveys of Elk in Northcentral Idaho

Abstract

Radio-collard elk (Cervus elaphus) were used to assess the importance of visibility factors during winter helicopter surveys in northcentral Idaho. Radio collars facilitated monitoring elk groups to determine whether elk were observed or missed during helicopter counts. Multivariate analysis indicated that visibility was significantly influenced by group size and vegetation cover. Snow cover, search rate, animal behavior, and different observers did not significantly affect visibility of elk. A sightability model was developed to predict the probability of observing elk groups during winter aerial counts.