Final answer:
The capture-recapture method relies on assumptions such as random mixing of marked and unmarked animals, marking not affecting recapture likelihood, and no harm from the marking affecting the animals. Using an example with field mice, this method can estimate population size, while considering behavioral influences and marking effects on survival rates.
Step-by-step explanation:
The capture-recapture method can be used to estimate population size, and it requires several assumptions to be made for the estimate to be valid. One key assumption is that the marked individuals released back into the population after the first capture have enough time to randomly mix with the unmarked individuals. This ensures that the sample captured the second time is representative of the entire population. Another assumption is that the marking does not affect the likelihood of the animals being recaptured, meaning it does not make them more or less likely to be captured again.
For instance, consider a scenario where 80 field mice are captured, marked, and released back into their habitat. Subsequently, another 100 mice are caught, and 20 are found to be marked from the initial group. These numbers can be used to calculate the overall population size using the formula: total population (N) = number in first catch (marked) x total number in second catch / number of marked recaptures in the second catch. In this example, the population size would be estimated as 400, calculated as (80 x 100) / 20.
However, there are important limitations to consider with the mark and recapture method. The behavior of the animals due to marking, such as avoidance or enticement back to traps, can affect the accuracy of the estimate. Furthermore, any harm caused by the marking technique may influence survival rates, altering the true population size.