Quadrat Method
A quadrat is a square frame of a known area, made of wood or metal.
It’s the most suitable estimation method for small plants e.g. grass and small slow-moving animals e.g. ants and snails.
The standard quadrat size is 1m2.
The choice of quadrat size used depends on the area, nature of habitat and the objective of the study.
A quadrat is thrown at random in a selected area.
Several quadrat counts are then made.
The total population is an estimate from the average.
In plants, it can be given in terms of the percentage cover.
Example
Below is an example of a population estimation of Bidens pilosa (Black jack plant)
5, 10, 3, 11, 12, 8, 6, 9, 7 and 13.
Area of study 43m by 15m.
1 quadrat = 1 m2
Determine the population of Black jack plants in the habitat.
Solution:
Total count = 5 + 10 + 3 + 11 + 12 + 8 + 6 + 9 + 7 + 13 = 84
Population per quadrat = 84/10 = 8.4
Total area = 43m X 15m = 645m2
Total population = 645 x 8.4 =5418 Black jack plants
Limitations of quadrat method
- Unsuitable for migratory animals;
- Unsuitable for large animals;
