Estimating population size and demographic rates from count data: Panacea or pipe dream?
Date:
Summary
Species monitoring programmes often record maximum counts of individuals to judge long-term trends in population size. However, we know that species detectabilies are never perfect, and that maximum counts are often a poor predictor of true population size. N-mixture models use repeated count data to estimate population size and changes through time, and present an appealing approach for analysing count data- however, applying these models to amphibian systems may not always be appropriate. Using simulations and data from several European amphibian species, I demonstrate some of the potential issues that can arise when using these models, and provide some general recommendations as to when the results from such modelling can be relied upon.