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Calcimator

Mark-Recapture Population Estimator

Estimate wild population size using the Lincoln-Petersen mark-recapture method with Chapman correction and confidence intervals.

Inputs

Results

Population Estimate (N)

300

Chapman Estimate282
95% CI Lower130
95% CI Upper470
Standard Error87
Recapture Rate16.7%
Sampling AdequacyAdequate
Marking Fraction16.67%
How to Use This Calculator
  1. Enter Marked in First Capture (M) — the number of animals marked and released.
  2. Record Total Second Capture (C) — all animals caught in the second sample.
  3. Count Recaptured Marked (R) — marked individuals in the second sample.
  4. Review Population Estimate (N) using the Lincoln-Petersen method and the Chapman corrected estimate.
  5. Check 95% CI Lower and Upper bounds — narrow the interval by increasing sample size (larger C).

How the result changes with Marked in First Capture (M)

Marked in First Capture (M)Population Estimate (N)
10,00160,006
35,001210,006
65,000390,000
90,000540,000

What each input means

Marked in First Capture (M)
Number of individuals captured, marked, and released in the first sampling event.
Total Second Capture (C)
Total number of individuals captured in the second sampling event (both marked and unmarked).
Recaptured Marked (R)
Number of previously marked individuals found in the second capture. Must be ≤ both M and C.

What each result means

Population Estimate (N)
Lincoln-Petersen estimate: N = MC/R.
Chapman Estimate
Bias-corrected estimate for small samples.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    Marked in First Capture (M) = 50, Total Second Capture (C) = 60, Recaptured Marked (R) = 10 = 3 input(s) provided
  2. Calculate Population Estimate
    Population Estimate
    300 = 300
  3. Calculate Chapman Estimate
    Chapman Estimate
    282 = 282
  4. Calculate 95% CI Lower
    95% CI Lower
    130 = 130

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