Chapter 19 Endangered Species 477 Copyright Goodheart-Willcox Co., Inc. Quadrat Analysis A quadrat is a frame (traditionally square) used in assessing animal or plant populations in a given area. Quadrat analysis is a method used to estimate a spe- cies population and determine its distribution over a random area using a set of similar quadrats (shapes). See Figure 19-14. Once data is gathered from multiple quadrats, the scientist can estimate the number and kind of species found in the larger total area. The same quadrats can be used over a series of years to monitor the presence or population of a species. This technique is not useful for studying fast-moving species because they will not remain in the quadrats. Quadrat analy- sis can be performed using mark-recapture, total counts, incomplete counts, and indirect counts. Mark-Recapture As explained earlier, the mark-recapture technique requires capturing, marking, releasing, and recapturing animals during repeated samplings. Mark- recapture is advantageous because an accurate count does not depend on the assessment of the amount of habitat. The disadvantage is that it does require capturing a large portion of the population. Total Counts Every member of a species in an area is counted when the total count or complete count method is used. This method is best used with animals that stay in the open, such as waterfowl or beach-dwelling seals. In a total count process, animals must be fl ushed out of hiding so that each individual can be counted. The process is labor intensive and expensive to perform. Aerial pho- tography can also be used to perform total counts. What disadvantages are there to quadrat analysis? How might errors be introduced to a quadrat study? Thinking Critically Figure 19-14. A small frame may be moved around an area to perform counts on small organisms. This student maps the locations of each quadrat he studies and compiles the information. Samib123/Shutterstock.com