Mark and Recapture Simulation

The figures above show the general procedure for simulating a mark-and-recapture session. Begin by choosing a population density (Figure 1). Start with a low density, then work up later. Then choose a vegetation density (Figure 2). You can try different vegetation densities, but it seems pretty clear that high densities are going to make the exercise more difficult, so why don't we just stick with the low density situation. Next, choose the vagility and mark color for your simulation (Figure 3). Vagility is a measure of the rate of movement of the animals. Those with higher vagility may wander from the test site, thereby affecting the reliability of your population estimate. Choose any mark color to for now. You're now ready to begin marking the animals. Press the Mark buttion. The cursor will change to a cross for marking animals (Figure 4, yellow circle). Left-click on the dots to mark them. As you mark, the number of marked animals will be incremented (Figure 4, blue circle). In addition, you have only 15 seconds to perform your first mart and the bar graph will show the time progress (Figure 4; red oval).

When the marking procedure has timed out, you should then press the release button, followed by the recapture button (Figure 5). You will have twice as much time to recapture animals. Depending on the vagility settings, some of your marked animals may have moved out of the test area (shown in the migration losses window). As you click on the  marked and unmarked animals (Yellow circle, figure 5), the number of recaptured (marked) and unmarked animals will be updated in the display. When the program has timed out, you can calculate your efficiency by pressing the calculate button (Figure 6). Here my estimate of 30 is way off from the real count of 102.

Run the simulation using the following procedure:

  1. Start with a low density animal population. Keep the vegetation density low and vagility low. Set your initial mark time as 15 seconds. Choose a dark green mark to make it difficult to find the animals (Figure 7). Eventually, you'll see the effect of mark color on the accuracy of your results.
  2. Use the CLEAR button between runs to re-zero the variables.
  3. Using the above starting points, run the simulation and record the estimate and actual population.
  4. Increase the collection time to in the following increments: 30 sec, 45, sec, and 60 sec. Which collection times gave you a better estimate?
  5. Using the best estimate collection times, change the original animal density to medium, then high. What effect does this have on your estimate?
  6. Next, using the best collection times and best density, determine the effect of increasing the vagility on your estimate.
  7. Finally, change the color to someting bright. What effect does that have on your estimate?