Many animals have well-defined stages of development. For insects, this is especially evident. Typically, an adult lays eggs. After a period of time, larvae emerge from the eggs. Larvae may go through several growth stages, 4 to 20 is common. These are called instars and are characterized by increasing larval size. The larvae pupate, and the adults emerge from the pupae. In the study of such populations, counts or estimates of the number of individuals in the various development stages are recorded at a series of points in time. Based on these data, researchers may want to estimate the total number of individuals that enter each stage, the average time spent in each stage, the survival probability for each stage, the mean entry time to each stage, or the unit time survival rate. A researcher may be interested in determining not only the mortality for each stage, but whether the mortality is density dependent. Interest may be focused on the stability of the population and factors affecting that stability. We refer to the statistical approach to answering these questions as life-stage analysis. Caughley (1977a), Southwood (1978) and Pedigo and Zeiss (1996) discuss life-table construction and the use of life tables in understanding population dynamics. Manly (1990) summarizes the statistical work in this area. These works serve as the foundation for much of this chapter.
KeywordsLife Stage Statistical Ecology Life Table Entry Time Single Cohort
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