# Capture Recapture Method

The Capture Recapture Method of sampling is used to try and estimate the entire population. A sample of animals are caught and tagged, their number noted, and then released back into their habitat. Later another sample is captured and the proportion of tagged animals in this sample should be representative of the proportion of tagged animals in the whole population, and then the total population size can be estimated using:

##### Total = original number tagged x total recaptured ÷ number tagged on recapture

Some examples of how to use this formula:

• 50 animals are caught and tagged and released. Later, 220 animals are caught and it is noted that 35 of these animals are tagged. What would be the total population estimate?

Total = 50 × 220 ÷ 35 = 314.28  so we can say approximately 314

• A biologist catches 100 deer in a forest, tags them and releases them back into the forest. A year later he catches 90 deer, of which 12 have tags. Estimate the total population of deer.

Total = 100 × 90 ÷ 12 = 750

## Total Population Calculator

To use the calculator, just enter the numbers in the appropriate boxes and press calculate to find the total population size

 Original Number tagged: Total Recaptured: Number tagged on recapture: Total: