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zoologists, a fuzzy definition of the space occupied by the population often forces an arbitrary
designation of the survey group, such as the "population" of robins nesting on your campus in the
spring. Knowing the number of animals in a designated study area is interesting, but we must bear
in mind that the ecological population is defined in terms of interactions among organisms of the
same species, and not by the ecologist's convenience.
After defining the individual and establishing the limits of the population you wish to count, your
next task is to choose a counting method. Arctic and prairie habitats lend themselves to accurate
survey by aerial reconnaissance. This approach works poorly in forests, at night, underwater, or in
soil habitats. If animals can be collected or observed in a standard time or collecting effort, you
can get an idea of relative abundance, but not absolute numbers. For example, the number of
grasshoppers collected in 50 swings with an insect net through an old field community produces
data that could be used to compare relative abundance in different fields, but would not tell you
how many grasshoppers were in the p...
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