Using mixtures to model heterogeneity in ecological capture-recapture studies

Modelling heterogeneity of capture is an important problem in estimating animal abundance from capture-recapture data, with underestimation of abundance occurring if different animals have intrinsically high or low capture probabilities. Mixture models are useful in many cases to model the heterogeneity. We summarise mixture model results for closed populations, using a skink data set for illustration. New mixture models for heterogeneous open populations are discussed, and a closed population model is shown to have new and potentially effective applications in community analysis.