The Lincoln Index. CAPTURE – MARK – RECAPTURE METHOD. The Lincoln Index. Used to estimate the size of an animal population. Capture animals Mark them with a tag Release them and wait a period of time Capture animals again. Assumptions.
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The Lincoln Index
CAPTURE – MARK – RECAPTURE METHOD
The population of organisms must be closed, no immigration or emigration.
The time between samples must be small compared to the life span of the organism
The marked organisms must mix completely with the rest of the population during the time between sampling.
The proportion of animals caught to the whole population is the same as the marked animals in the second sample.
First Capture = Marked animals, second capture
Whole populationsecond capture
Solve for N = n1. n2 to find the total population
Woodlice are terrestrial crustaceans that live under logs and stones in damp soil. To assess the population of woodlice in an area, students collected as many of the animals as they could find, and marked each with a drop of fluorescent paint. A total of 303 were marked. 24 hours later, woodlice were collected again in the same place. This time 297 were found, of which 99 were marked from the first time. What is the estimated population of woodlice in this area?
probably in the area examined?
n1 = number in the “first sample” and marked.
8+19+10-2 = 35
You need to know how many animals were marked!
n2 = number in the “second sample” 23
m2 = number in the second sample with a mark 8
N = 35x23 = 100.6 The size of the population is 101 as 8100.6 voles is impossible!
pond turtles1992: 18
1993: 34 (12)
1994: 30 (18)
1992-93: N = 18(34) = 51 turtles
The total number marked is 18 + 34 – 12 = 40
1992-94: N = 40(30) = 67 turtles
This assumes that none of the paint came off of the turtles over the course of two years.
Does the size of the first capture, n1, while the size of the second capture is held constant, affect the accuracy of the population estimate, N?
Does the size of the second capture, n2, while the size of the first capture is held constant, affect the accuracy of the population estimate, N?
You will use beans instead of animals to study the accuracy of the Lincoln index.
Vary either the size of the first capture OR the second capture while holding the other variable constant
The value for m2 will change, so the value for N will change…. maybe