Since every individual (except identical twins) possesses a unique
multilocus genotype, it is possible to determine the number of individuals sampled and, through the use of statistical models,
to estimate population size. The approach most commonly used
to analyze non-invasive DNA-based data is capture–mark–recapture
(CMR). Nevertheless, use of non-invasive DNA-based methods
can be problematic because of the low quantity and quality of DNA
contained in such samples. Two main types of scoring error, allelic
dropout and false alleles, can lead to incorrect genotypes and consequently
to biased estimates.Fortunately, several methods have been proposed to counter
these problems.