Estimating the size of the Adult Population

Abstract

Several mark–recapture methods for the estimation of population size have been developed as an alternative to counting the number of individuals within a fixed unit of habitat in order to determine absolute population size. Methods have been developed that are applicable to closed populations, in which population size is assumed not to be affected by immigration (including birth) or emigration (including death), and open populations, in which immigration and emigration occur. The application of mark- recapture methods to closed systems requires only one recapture occasion, while the study of open systems requires two or more recaptures. Available methods may be either deterministic, assuming an exact value for survival rate of individuals over the sampling interval, or stochastic, reflecting the more realistic scenario where an individual’s survival over the sampling period is described as a probability. The main disadvantage of markrecapture methods is the requirement to capture a relatively large proportion of the population in order to achieve acceptable levels of accuracy.