Since it is usually impossible, and often impractical, to count all individuals in a population, researchers use a variety of sampling techniques to estimate population densities.
One method is to count the individuals in a certain area.
The larger the number and size of sample plots, the more accurate the estimates.
Population densities may also be estimated based on indirect indicators such as animal droppings or tracks, nests, or burrows.
how can you estimate the number of certain individual by just looking on their droping like their pellets.