Population Growth Rate Problem: Researchers want to estimate the population size of Blanding’s turtle in Illinois

Question

Researchers want to estimate the population size of Blanding’s turtle in Illinois. If they caught and marked 14 individuals on the first count, and 20 individuals on the second count, how many individuals must have been marked for an estimated total population of 70? Round off to the nearest whole individual.

Answer 1

The most straightforward way to find this answer is to use the Lincoln-Petersen index, which is commonly used for mark-recapture population studies but is most effective in a closed population.

The Lincoln-Petersen formula is: N = (M × C) / R

Where:

1. N = total population estimate
2. M = number marked in first sample
3. C = total number captured in second sample
4. R = number of marked individuals recaptured in second sample

You could just plug in the numbers here, but as with any statistical evaluation, it is important to understand the assumptions and limitations. The major assumption here is that the sampled population remains constant between samplings (i.e., no births, deaths, immigrations, or emigrations), then the Lincoln-Peterson index will not provide accurate results. In essence, the Lincoln-Petersen index provides a relatively straightforward way to estimate population size under specific conditions, but it's crucial to be aware of its limitations and assumptions before applying it.