Let’s Measure Overlap for Grevy’s Zebra and Cape Buffalo

In this case the calculation is:

Sorenson's index formula $\frac{2 \times number of shared plant species = 2 \times 5 = 10}{2 \times no. of shared species + no. species for zebra (animal 1) only + no. species for buffalo (animal 2) only = 10 + 7 + 7 = 24}$

Sorenson's index answer $10 / 24 = 0.42$

Sorenson’s index values range from 0 to 1. High values indicate high overlap, while low levels indicate little overlap.

To express overlap as a percentage multiply the index values by 100. The diets of the zebra and buffalo overlap by 42%.

Image of Venn Diagram showing all the plant species found in dung samples from Grevy's Zebra and Cape Buffalo. — Venn Diagram showing all the plant species found in dung samples from **Grevy's Zebra** and **Cape Buffalo** (Plant species in green and marked with an asterisk (*) are grasses and those shown in black are browse.) Show data in table view