The Use of Mixed Logit Models to Reflect Heterogeneity in Capture‐Recapture Studies

Abstract

Summary. We examine issues in estimating population size N with capture‐recapture models when there is variable catchability among subjects. We focus on a logistic‐normal mixed model, for which the logit of the probability of capture is an additive function of a random subject and a fixed sampling occasion parameter. When the probability of capture is small or the degree of heterogeneity is large, the log‐likelihood surface is relatively flat and it is difficult to obtain much information about N. We also discuss a latent class model and a log‐linear model that account for heterogeneity and show that the log‐linear model has greater scope. Models assuming homogeneity provide much narrower intervals for N but are usually highly overly optimistic, the actual coverage probability being much lower than the nominal level.