We’re often asked about why it is important to quantify animal diet.

One reason is that it helps us understand he mechanisms by which animals acquire scarce resources. The diet of animals determines their ability to grow, fight off disease, and reproduce.

Bison in North America are more limited by protein in their diet than energy throughout most of the year.

Briefly, below is a graph from Gaddy Bergman’s data of the relative abundance of different non-grass species in the diet of bison over the course of the year from Konza Prairie.

Although bison are considered to primarily consume grasses, as sequencing of plants in bison fecals reveal, bison are shifting through different high-protein plant species over time.

All of the non-grasses that are showing up have high protein concentrations in their leaves. The progression through species broadly matches the differences in the phenology of the species. As new high-protein species become available in the grassland, the bison switch their diet to consume the newly-available species.

Knowing this, we see that many plants are critical resources for bison. They may not be abundant on the landscape, but bison seek them out to supplement their diets.