Capture-recapture methods and models: Estimating population size

This book chapter describes ecological capture-recapture studies and associated models often fitted to capture-recapture data to obtain estimates of total population size. Such estimates can be important for numerous reasons, including for example, conservation and management purposes. We focus on different forms of heterogeneity that may affect the propensity of individuals to be observed within the study period. Failing to account for such heterogeneity can lead to significant bias in the population estimates. We consider different types of heterogeneity corresponding to recorded (discrete-valued) covariates/characteristics of individuals that are observed within the study period; in addition to unobserved heterogeneity in the form of mixture distributions. The different models are motivated and discussed, including the specification of the likelihood functions, before being applied to a real dataset. Finally we conclude with a discussion including the modern challenges which are arising due to technological advances.