Non-Selective Grazers
September 22, 2026
A topic was brought up the other day I hadn’t heard before but worded as if that was a common notion about bison. “I’ve heard bison push out the deer and elk...” the prompt began. In other words, can a bison ranch boast a healthy population of other ungulates? Or do bison outcompete and limit the resources to the point that sympatric animals like deer and elk will not make the pasture a part of their habitat?
With the need for space to roam, similar food source, and the fencing required for bison, it is an understandable question, just not one I had ever given much thought. I observe undulates sharing space frequently.
It is estimated that there were once 30-60 million bison on the continent. This estimate is one to two times the number of deer now. So how did huge mob-grazing herds of bison, each individually weighing about half a ton, allow for other ungulates?
Well, for one it is a testament to the huge amount of energy stored in healthy grasslands. Second, bison are non-selective grazers. This does not mean they can and will eat everything in their path. Amazingly, in feedyards, the animals can be given the option of different feeds or "choice fed" and selectively choose what they need to avoid bloat and maintain proper weight gain. In pasture, they can balance protein and mineral intake by which plants they eat during which season. And the term likewise does not mean they’ll self-regulate overgrazing. They prefer short, green grass just starting to grow and will stay in those areas if given the chance.
Bison are non-selective in the sense that when they eat an area of their choosing, the size of their mouth is too large to dial in and fine tune to an individual plant or plant part. Taking large mouthfuls at a time, the animals will mow the dominant bluestem making room for forbs to grow. They also spend more time ruminating while resting in the field. It’s clear the pronghorn are closely tied with the bison movement on our pasture, with the bison being dominant. The pronghorn follow along the trail made by the bison, grazing behind them. The pronghorn are the clean-up crew. After the bison move through, the pronghorn can easily use their narrow snout and mouth to feast on the leaves, stems, and seed heads now uncovered after the area has been grazed. Selective grazing. Selecting the flowering plants and shrubs the bison tend to eat around. Over half the pronghorn diet is forbs, and then sage, not grasses. Similar with the deer. They prefer forbs and shrubs, their narrow muzzle so specialized, it allows them to pluck berries off cacti and leaves and twigs off woody plants.
In a 30-year study from Kansas State, plots grazed by bison were up to 103% more diverse than that of cattle. The plots had more forbs. Why is this important? Because it's a food source for other native animals and insects and because forb roots complement the roots of grasses, helping anchor soil, returning nutrients to the soil, providing habitat for nitrogen-fixing bacteria, and allowing the prairie soil to hold a vast amount of carbon.
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