Biology: Mark and Recapture

Created Feb. 7, 2024 by Arthur Chang

Names:_______________________ & _______________________               Date:_______________

Animal Studied: ________________

First visit

Captured and marked _______ individuals with a black mark on the right back leg.

Second visit

Captured _________ total individuals of which _________ were marked.

Calculation

Using the Petersen–Lincoln index, estimate the total population from your experimental data:

Total \space Population=\frac{(1st \space Capture)*(2nd \space Capture \space Total)}{(2nd \space Capture \space Marked)}


Total \space Population = \frac{(\space\space\space\space\space\space\space\space\space\space\space\space)*( \space\space\space\space\space\space\space\space\space\space\space\space )}{( \space\space\space\space\space\space\space\space\space\space\space\space )}\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\\ \\ \\ Total \space Population = (\space\space\space\space\space\space\space\space\space\space\space\space\space) \space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space


Discussion

Now that you have performed a mark and recapture study, what do you think are some limitations to this method? Are there animals you think this technique would not work well on, and why?




Why do you think it is important for our sampling (catching) to be random and representative of the population? What would happen if we intentionally caught the exact same individuals on our first and second visits? Would we be able to estimate the total population with that data? What if the marked individuals intentionally avoided the traps on our second visit?




Why do you think we waited a week before going back to recapture the animals? Can you think of an animal that you would want to wait longer to recapture? Shorter?




Based on the Petersen–Lincoln index, can you determine what would happen to our estimation if half of the individuals we marked wash off the marking between the first and second visits? (hint, what happens when the denominator becomes smaller?)




What would happen to our estimation if a large number of individuals are born between our first and second visit? What if a large number died? Would that actually be a problem for our estimation?




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After the class has counted the actual population size, how did your estimate compare? What could you do to increase the accuracy of your estimation?




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