Cricket Mark-Recapture Investigation

1. Cricket Mark-RecaptureInvestigation

2. How do we estimate the number of animals out there? • •Elk? wolves? • •One method: mark-recapture • –Using Lincoln-Petersen technique • •1) capture animals & mark all that you caught • –Release these animals • •2) capture again and count the number of marked animals

3. What do we need to think about to capture and mark animals? • •How are fish caught? • •How are they marked, or tagged? • •How are birds caught? Marked? • •How would you mark a cricket? • •The mark depends in part on how long it needs to last

4. Insect/Cricket Anatomy

5. Terms we need to know • • N= estimate of population size • • n1= # animals marked and released 1sttime • • n2= # animals captured 2ndtime • • m2= # animals with marks at the • 2ndsession∧N

6. APES 1/7/11 • QUIZ on 8/9 Monday • Finish up the Mark and Recapture Population Lab • Make sure to be working on your learning targets for Chapter 9 • FRQ soon…….

7. Sample calculation • A biologist wants to estimate the size of a population of turtles in a lake. She captures 10 turtles on her first visit to the lake, and marks their backs with paint. A week later she returns to the lake and captures 15 turtles. Five of these 15 turtles have paint on their backs, indicating that they are recaptured animals. • N = n1*n230 = 10 x 15 • m2 5 • In this example, the Lincoln–Petersen method estimates that there are 30 turtles in the lake.

8. Assumptions • •Population is closed • •Marks are not lost or overlooked • •All animals are equally likely to be captured both times –Example: trap happy animals • n1 = m2N= n1*n2 • N = n2 m2 • If m2is increased, what happens to N?

9. 95% Confidence Interval • Standard error equation: • •Subtract /Add 2 * S.E. from N to get 95% Confidence Interval S.E= ˆN (ˆ N −n1)(ˆ N −n2) • n1n2(ˆ N −1)ˆ