Populations are counted with different frequency depending on available resources, decreasing the risk of disturbance to counted populations, and other logistical considerations. The impact of variation in counting frequency on the accuracy of estimates of population growth rate are not fully appreciated, and need to be balanced against the possible impacts of disturbance. We examined counts of multiple species of hibernating bats to determine whether there was any evidence of disturbance effects due to more frequent counts and the extent to which less frequent counts increased the uncertainty in population growth estimates.
Results/Conclusions
We found little evidence that more frequent visits to hibernating bat colonies decreased population growth rates for multiple species of bats. At the same time, decreasing count frequencies substantially increased the uncertainty in population trend estimates which reduced the power to detect trends in the same amount of time. These results suggest that limitations on count frequencies when counts are relatively infrequent (e.g. yearly) and relatively short in duration may have adverse impacts on one of the key goals of population monitoring - to detect trends in populations.