The Estimation of Population Size with Equal and Unequal Risks of Capture

Abstract

Behavioral characteristics and microhabitat distributions of individuals may cause heterogeneity in their risk of capture in field studies of the dynamics of natural populations. The number of recaptures of marked individuals can be used to test for equicatchability by their fit to a Poisson distribution. If the null hypothesis of equal risk of capture is rejected the number of captures per individual may follow a negative binomial distribution. The use of truncated distributions to estimate the number of transients in the population, or the number of animals never caught is found to be of very limited value. These methods are applied to an original set of capture histories from a study of a population of the painted turtle, Chrysemys picta.