It has to do with the trophic level. https://en.wikipedia.org/wiki/Trophic_level https://en.wikipedia.org/wiki/Trophic_level Plants are almost always level 1.

It has to do with the trophic level. https://en.wikipedia.org/wiki/Trophic_level https://en.wikipedia.org/wiki/Trophic_level Plants are almost always level 1. Bison would be just a bit over 2. (a bit over because they may consume bugs, bones, etc.) Humans would usually be higher than that. The traditional Eskimo diet is nearly trophic level 5. Due to loss of energy going from one level to the next, the biomass of creatures with high trophic level is limited: https://en.wikipedia.org/wiki/Ecological_pyramid https://en.wikipedia.org/wiki/Ecological_pyramid