Bison Population Estimates

Population surveys are conducted in mid-summer and mid-winter. Estimates are arrived at by conducting aerial counts in the areas with the highest probability of having bison in them. The data are analyzed using correction models that account for the probability that a certain number of bison will not be detected. Obtaining an accurate count is usually more difficult in the winter when animals are more likely to congregate in thermal areas, because detection of dark-colored animals on a dark background and animals hidden by steam or fog can be difficult. The variation in counts conducted during different flights is much greater during winter than summer.