Testing interdependence of rodent population and cereal plant density
Candidate name: Glakho Robakidze
Candidate number: European School (code 6343)
Session: May 2017
My personal interest In this experiment I investigated the correlation between the presence of rodents and the coverage of the field by cereal plants. I like hiking and often while hiking I come across rodent holes in grassy meadows, so I thought about the dependence of grasses (mainly cereals) and rodent population and decided to make my personal investigation about this topic. This topic is interesting for me, because I am interested in the biodiversity and also sometimes while hiking I like to look for holes and count them. This topic was interesting for me
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Variables
Controlled variables Area of each quadrant(m2)
The total area of the fenced territory(m2)
Dependent variables Number of rodent holes
Independent variables Percentage of plant coverage (%)
Risk assessment Before the analysis I wanted to state that there were no health and environmental risks to be considered during the experiment. It was held ethically with no threat to the environment.
Method
1) I found a place, fenced reclaimed territory (former clay quarry) of Heidelberg cement Georgia (I had permission to go there). Grazing was avoided and grass was sawn in 2012.
2) I measured each fenced territory which was 525m2
3) I defined quadrants with the area of 25m2 for each
4) I first looked at the coverage of the ground by cereal grasses and then counted rodent holes on the quadrant.
5) I collected data from 7 quadrants from each fenced territory.
6) The total area of the 14 quadrants was 350m2
Raw data
Quadrant
Ground coverage Holes
1 50 0
2 80 2
3 80 0
4 80 8
5 80 4
6 90 9
7 90 3
8 90 0
9 90
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The percentage of plant coverage varied from 50 to 95 percent. Chi squared was used in order to determine if ground coverage and number of rodent holes correlated By analyzing the gathered data, I conclude that the plant coverage of the ground has a positive correlation with the size of the population of rodents (common vole in question). Graph 1 evidently shows that as the plant density grows the population of rodents multiplies. However, at higher density rates (80% and more), there is no statistically significant interdependence between number of holes and density. This is also supported by results from chi squared and R2. My theory was proven right.
Evaluation
While the experiment was conclusive I want to state the weaknesses of the conclusion. There may be errors in the data regarding the population of rodents because during the experiment single hole was counted as a single individual, but that might not be true as certain individuals might use several holes, also the data regarding the plant coverage may have errors as well because the percentage of coverage was set by eye measurements as I didn’t have any better methods to use.