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
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
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
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.