Monitoring+page

**Monitoring populations** is an important way to learn the status of threatened or endangered species. Scientists and volunteers collect census information using several techniques. The most common types of monitoring are inventories, studies and surveys:


 * **Inventories** - counting the number of individuals present in a population. This works well when the subjects are stationary and easily identified;


 * **Surveys** - using a repeatable sampling method to estimate the number of individuals in part of a species' range. This is the method most often used to estimate the number of Puritan tiger beetles. Biologists estimate that the actual population size is two times the count taken in surveys performed by scientists and volunteers from shallow water using binoculars, studying the beach habitat during mating season (24);


 * **Demographic studies** - follow individuals to determine rates of growth, reproduction, and survival.