Population estimation by the removal method assuming proportional trapping

Abstract

Moran (1951) proposed an approximate formula for the likelihood of the size of an animal population when the ‘removal method’ is used. We here obtain an exact formula for the likelihood, based on an assumption of ‘proportional trapping’ of animals. The formula is ill conditioned and requires extremely high precision arithmetic for its numerical evaluation. A form of minimum chi-squared or weighted least-squares method is also given for estimating population size. For this method the calculations are not badly ill conditioned, and the method cuts down the work required for finding the maximum likelihood solution.