Animation 53.1: The Mark-Recapture Method

INTRODUCTION

Determining the size of a population is sometimes difficult, especially for a population of highly mobile organisms. In this animation, we show the mark–recapture method, which is useful for estimating the sizes of such populations. In this method, a population sample is captured, and the individuals are counted and marked before they are released back into the population. The number of marked individuals that are later recaptured in a second sample provides a clue to the overall size of the population.

CONCLUSION

The mark–recapture method is useful for estimating the size of a population of highly mobile organisms. A sample of the population is captured, marked in some way, and then released back into the population. The marked individuals are a certain proportion of the total, so that when a second sample is taken, the number of marked individuals captured again should represent the same proportion of the second sample. For this method to be most accurate, enough time must elapse between the two samplings so that the marked individuals mix throughout the population. However, not so much time should elapse for births, deaths, or immigration/emigration to significantly affect the population size.

Textbook Reference: Key Concept 53.1 Populations Show Dynamic Variation in Size Over Space and Time