Final answer:
The Lincoln ratio, used for estimating population sizes in mark and recapture studies, assumes that marked individuals stay within the same location for both captures. However, this may not be true due to migration, dispersal, trap avoidance, or marking effects. Calculating populations using the ratio requires consideration of these factors to avoid violating assumptions.
Step-by-step explanation:
The Lincoln index or ratio, commonly used in mark and recapture studies, assumes that all individuals marked in the first round of capture are equally likely to be captured in the second round. However, this may not always be true, particularly in the study of mobile and wide-ranging species. One key issue is that marked individuals may not stay within the same location between captures; they may migrate or disperse to different areas, thus they may not be present in the location targeted for the second capture. Other factors such as animals learning to avoid traps or acquiring greater susceptibility to capture, as well as potential impacts of the marking process on the animals’ behavior and survival, can also violate the assumptions of the technique.
The original population size is often calculated using a formula that incorporates the number of individuals captured, marked, and recaptured. For example, if 80 lemurs are captured, marked, and released, and then a second sample of 49 lemurs is captured with 11 marked individuals found among them, the estimated population size can be calculated as (80 x 49) / 11, leading to an estimated number of lemurs in the original population. Using the Lincoln ratio can be a powerful tool for estimating population size, particularly when direct counts are impractical, but researchers must carefully consider and attempt to account for the factors that might lead to violating the underlying assumptions of uniform mixing and equal catchability.