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Unformatted text preview: opulation.
For estimates of absolute numbers, mark-recapture methods can be very effective. The first step
is to capture and mark a sample of individuals. Marking methods depend on the species: birds can
be banded with a small aluminum ankle bracelet, snails can be marked with waterproof paint on
their shells, butterflies can have labels taped to their wings, large mammals can be fitted with
collars, fish fins can be notched, and amphibians can have nontoxic dyes injected under the skin.
Marked animals are immediately released as close as possible to the collection site. After giving
the animals time to recover and to mix randomly with the whole population, the ecologist goes out
on a second collecting trip and gathers a second sample of the organisms. The size of the
population can then be estimated from the number of marked individuals recaptured on the
second day. Biology 6C 67 The assumption behind mark-recapture methods is that the proportion of marked individuals
recaptured in the second sample represents the proportion of marked individuals in the population
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