Animals tend to move around so it is harder to estimate the population size.Some animals may be hidden at any given moment.The capture-mark-release-recapture technique can be used to estimate animal population size.Individuals are captured, in a certain area and marked and then released back into the community. After a given amount of time so they can redistribute through the habitat a number of individuals are recaptured. The number of marked individuals are counted. The population size is given by the number of individuals in the first catch, multiplied by the number of individuals in the second catch, divided by the number of marked individuals in the second catch.