Mark-Recapture Calculator (Lincoln-Peterson)

The Mark-Recapture Calculator (Lincoln-Peterson) estimates the total size of a wildlife population by comparing how many marked animals are recaptured in a second sampling — a standard technique used in ecology and conservation fieldwork. Enter the number of animals marked in the first capture (M), total animals in the second capture (C), marked animals recaptured (R), and your chosen confidence level. You'll get the estimated population size (N), standard error, confidence interval, and estimated capture probability.

Number of animals captured and marked in the initial sampling

Total number of animals captured in the recapture sampling

Number of previously marked animals found in the second capture

Results

Estimated Population Size (N)

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Standard Error

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Confidence Interval (Lower)

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Confidence Interval (Upper)

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Estimated Capture Probability

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Frequently Asked Questions

What is the Lincoln-Peterson estimator?

The Lincoln-Peterson estimator is a statistical method used to estimate the size of a wildlife population using mark-recapture data. It assumes that the proportion of marked animals in the recapture sample represents the proportion of marked animals in the entire population.

What assumptions does the mark-recapture method require?

The method assumes: (1) the population is closed (no births, deaths, immigration, or emigration), (2) marks are not lost, (3) all animals have equal probability of capture, and (4) marking does not affect recapture probability.

How accurate is the population estimate?

Accuracy depends on sample size and how well the assumptions are met. Larger recapture samples generally provide more accurate estimates. The confidence intervals help indicate the reliability of the estimate.

What if I recapture no marked animals?

If R = 0, the Lincoln-Peterson estimator cannot be calculated as it would involve division by zero. This suggests either a very large population or violations of the method's assumptions.

Can this method be used for any animal species?

Yes, but it works best for species that can be safely captured, marked, and released without affecting their behavior or survival. It's commonly used for fish, birds, small mammals, and some insects.

What does capture probability tell me?

Capture probability indicates how likely an individual animal is to be caught in a sampling effort. Low capture probabilities may indicate the need for different sampling methods or longer sampling periods.

How long should I wait between capture sessions?

The time between sessions should allow marked animals to mix randomly with the population but be short enough to maintain population closure. This varies by species but is typically days to weeks.