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Researcher's Results

Research Question 3

Research Goal:

The goal of this research is to understand the impact vicuna grazing has on the growth of vegetation by fencing areas to prevent grazing.


Several hypotheses could be posed here. Some examples include:

  • Grazing by vicunas results in vegetation being shorter in habitats where grazing pressure is higher.

  • Because vicunas prefer some plant species over other species, there will be fewer species of plants present where vicunas feed.

  • Vicunas kill plants when they feed on them; therefore the number of plants alive will differ in habitats that differ in vicuna grazing pressure [This last possibility is fair; however, vicunas do not kill plants when feeding on them].

All of these could be combined in a variety of ways, and there are other ideas that are also possible hypotheses.  However, for this exercise, we will choose the first hypothesis.

Predictions for the Chosen Hypothesis:

  • Vegetation height will be greater inside fenced areas, where vicuna grazing is not allowed.
  • Vegetation height will be shorter outside fenced areas, where vicuna grazing is allowed.

Data analysis:

Data Table
In the table , each value is the average of the five plant heights for each site.
For the control value in site 1, the result came from the calculation
(3 +1+3+4+5)/5 = 3.2.
The grand average represents the average of all values in each column.
For the grand average of the control values, the result came from the calculation
(3+1+3+4+5+1+8+6+6+6+2+10+9+6+7+7+2+9+10+8+6+9+7+4+10)/25 = 5.92.

The grand averages for the controls and the exclosures are the two values that need to be compared in evaluating the hypothesis and predictions.


Describe the plant heights for the plants measured inside and outside the fenced areas.

Plants inside fenced areas were an average of 20.28 inches tall. Outside the fenced area, they averaged 5.92 inches tall. The plants inside the fenced area were 3.4 times taller on average than plants outside fenced areas.

Were your hypothesis and predictions confirmed by the data?

Yes, the hypothesis that grazing by vicunas results in vegetation being shorter in habitats where grazing pressure is higher was confirmed. Both of the predictions about the height of plants inside and outside the fenced areas were confirmed as well.

What is your explanation for the differences in plant height?

Clearly, less grazing (decreasing pressure) by vicunas results in plants being higher. This occurs because the new tissue added by plants actually stays on the plant instead of being consumed by vicunas.

Time to Use All You've Learned to Synthesize and Report Your Results!

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