1. Cricket Mark-Recapture Investigation

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 1st time
• n2= # animals captured 2nd time
• 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. N = n1*n2 30 = 10 x 15 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*n = 10 x 15 m
In this example, the Lincoln–Petersen method estimates that there are 30 turtles in the lake.

8. Assumptions n1 = m2 N = n1*n2 N = n2 m2 •Population is closed
•Marks are not lost or overlooked
•All animals are equally likely to be captured both times
–Example: trap happy animals
n1 = m N = n1*n2
N = n m2
If m2 is 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