You want to estimate the number of canvas backs (a type of duck) at the Sacramento Wildlife Refuge. In two days you capture 200 canvas backs, mark all of them and release them. One month later you capture another 200 canvas backs, of which 100 were marked by you last month. Calculate an estimate for the population size of canvas backs.

A. 400

B. 100

C. 200

D. 300

E. 600

Option A 400 individuals

Explanation:

Using this formula, we can estimate the population size of the canvas backs as this is a capture-recapture method.

N = (MxC) / R

Where N = estimated Number of individuals in the population

M = number of individuals captured and Marked = 200

C = total number Captured the second time (with and without a mark) = 200 and

R = number of individuals Recaptured (those with a mark) = 100

Thus, we have

N = (MxC) / R

= (200 x 200) / 100

= (40,000) / 100

= 400 individuals.