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: How are animal populations counted? Like how do you know how many owls there are on Earth?

In: Biology

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One method, is to capture and tag part of a population, and then release them back into the population. The next season you capture part of the population again, and based on the percentage of the second capture that was previously tagged and then re-captured in the second capture session, you can mathematically estimate the total population.

Known as the recapture method of population estimation.

https://en.wikipedia.org/wiki/Mark_and_recapture?wprov=sfla1

Unless a population is so extremely small that it is close to extinction, you generally don’t count every single individual but instead estimate the total size of the population based on samples and various observations that can be used to infer an estimate of the total number of individuals.

1. Find the area that the animals are found in.

2. Divide that area up into subsections.

3. Pick a small sampling of those sections at random.

4. Count the number of animals in those sections.

5. Take the average number of animals in each section of land and multiply by the number of sections. That gives you a reasonable estimate of how many animals there are there in total.

There are some more advanced techniques you can use, but that’s generally the gist of it. In essence, you’re trying to understand how likely you are to find an animal in a given area to understand how many you can reasonably expect to be in a larger area.