Section 6. Evaluating the Model (Part 1)

The Model

The graph below is the logistic model you have been working with. It was developed using data collected in KNP. To reveal the actual data recorded by park wardens and biologists, click here.


Graphical representation of the number of African bush elephants from 1903 to 1996 in Kruger National Park, South Africa based on the figure and data reported in KNP Proposed Elephant Management Plan by White, I., Biggs, H., Gaylard, A. and Braack, L. (South Africa National Parks (

Actual Data and Model

The actual data (in green) show that African bush elephants did in fact grow logistically in the park. The data has the characteristic S-shape of the logistic model: population growth rate (ΔN/Δt) was slow at first, became rapid, and then levelled-off.
However, if you compare the model (gray curve) and the actual data (green line), you will see that the model does not mirror the actual data perfectly.
Think about why this is the case, then click “Next”.