During a field study on population dynamics in a secondary forest plot in Ogun State, 80 A… — JAMB UTME

During a field study on population dynamics in a secondary forest plot in Ogun State, $80$ African giant land snails (*Archachatina marginata*) were captured, tagged, and released back into their habitat. A fortnight later, a second sample of $50$ snails was collected, revealing that $16$ of them bore the original tags. What is the estimated total population size of these snails in the forest plot using the Lincoln Index?

Answer: 250 snails

Answer

The estimated total population size of snails in the forest plot is 250.

The estimated total population size

N

is calculated using the Lincoln Index formula

N = \frac{M \times C}{R}

, where

M = 80

(initially marked),

C = 50

(second capture total), and

R = 16

(recaptured marked). Substituting these values yields

N = \frac{80 \times 50}{16} = 250

snails.

Step-by-Step Solution

Extract the given sample data for the Lincoln Index variables.

Initial marked count (

M

) = 80, second sample total (

C

) = 50, recaptured marked count (

R

) = 16.

The mark-release-recapture method relies on the proportion of marked individuals recaptured in the second sample.

Set up the Lincoln Index equation.

N = \frac{M \times C}{R}

This formula assumes that marked and unmarked individuals mix randomly throughout the population and have equal probability of recapture.

Calculate the estimated population size (

N

N = \frac{80 \times 50}{16} = \frac{4000}{16} = 250

Performing the arithmetic yields the estimated total population size.

Key Concept

Population Estimation using Mark-Release-Recapture (Lincoln Index)

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