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Visual counts frequently are used to census ground squirrels before and after a control program. However, the precision of visual counts is not known. During 1979 and 1980 I compared visual counts of Richardson's ground squirrels (Spermophilus richardsonü elegans) with mark-recapture population estimates on a study area near Kremmling, Colo. There was no significant correlation between the population estimate generated over a five-day trapping period and the highest visual count on a particular day within that period (R = 0.42, P = 0.06). However, there was a significant correlation between the population estimate and the highest ground squirrel count during the five-day period (R = 0.65, P = 0.009). Therefore, if certain guidelines are followed, visual counts may be reliable indices of ground squirrel populations.
mark-recapture, population estimates, Richardson's ground squirrels (, Spermophilus richardsonü elegans, ), vertebrate pest control, visual counts
Research biologist, U.S. Fish and Wildlife Service, Denver Wildlife Research Center, Denver, Colo.