The calculations involved in the assessment of animal population density is fairly straightforward. But reasonable estimates requires accurate raw data. A sample must be taken where each animal has an equal chance of capture, and the sample population to randomly reassign themselves when re-released. While marked animals must remain selected, the second sample to be taken quickly to minimize the effects of births, deaths and migration on population size. For sedentary populations, small tests-known as square-must be fairly representative of the entire population. Additional square sampling may be necessary if the data shown for varied.
Things you need
- Population data
- Defined test area
Calculation of Mobile Animal Population
1. Use Lincoln-Peterson index to calculate density. This simple, capture-recapture method has been used effectively since the 1930s.
2. Assign variables. N (number) is the number you are looking for, the total number of animals. Use m (selected) in order to represent the number of animals taken in the first capture and mark. Use r (noted) that represent the number of recaptured animals. Take advantage of n represents the number of animals captured for the second time.
3. Apply the Lincoln-Peterson index, which States that the percentage of selected individuals for the total population must be equal to a percentage of noted individuals to recaptured population. This statement is represented by the formula m/n = r/n.
4. Rearrange the equation to solve for the total population number. The formula will be N = mn/r..
5. Consider using a standard deviation equation to check for accuracy. This will give an error margin that allows you to specify the population with scientifically recognized trust. Use this formula-S = square root of ((m + 1) (n + 1) (mr) (nr)/(R + 1) (n + 1) (n + 2))-in order to calculate the standard deviation.
6. Interpret the standard deviation calculation. Keep in mind that the greater the deviation, the less accurate estimates of actual population is. For example, with an estimated population of 500, a confidence interval of +/-25 (475-525) is more accurate than one of +/-. 100 (400-600).
Calculation of Sedentary Animal Population
7. Use a square technique to generalize population density estimates from several small areas into a bigger one. A square is a small area where the actual animal population is counted.
8. Check the data to ensure that the number, size and arrangement of the square is reasonably likely to be representative of the population as a whole. For example, if you taste four square and we have two animals, one has 800 animals, and two others have 57 animals, you might have to call into question the sampling method.
9. Average number of persons found in each square. Using the above results in an average of 229 individuals per square sample. (2 + 800 + 57 + 57)/4 = 229.
10. Multiply the average number of available by the ratio of the larger surface area to the square size (they should all be the same). For example, if your test area is 200 m2 and each square is 2 m2, calculate the ratio is 200 m2/2 m2 = 100.
11. Assessment population density by multiplying the average number of animals per square of area ratios obtained. For example, the population density in this sample is calculated by multiplying the 229 with 100 for coming up with 22900 persons.