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Bison in Yellowstone: Where to See Them & Their History


By Kody Goodwin

If you are thinking of visiting Yellowstone National Park the first thing that comes to mind might be Old Faithful. If you are like me, maybe it’s the wildlife of the area that calls you to visit. Over 67 mammals and 150 birds live and breed in Yellowstone! One mammal in particular is very important to Yellowstone’s ecosystem. Can you guess which one? You might know it as the American Buffalo. In the park, scientists call them by their scientific name Bison bison or just bison is fine too. 

The American Bison

In the past bison roamed grasslands across the nation before pilgrims landed at Plymouth Rock. There used to be 30 to 60 million bison grazing across the bison belt. The bison belt stretched across our continent, from Alaska to the Gulf of Mexico. We knew very little about their important role in our ecosystem at the time and the bison belt has changed drastically in the last 200 years. 

After the Louisiana Purchase bison numbers began to decrease in the early 1800’s. Settlers and trappers headed west in search of a better future and a thicker wallet. After 1860 their numbers began to plummet due to soldiers, sport hunters, and fur trappers killing almost 5000 bison a day. In 1889 the population in Yellowstone was estimated to be less than 200. By 1900 some texts suggest poachers hunted that number down to two dozen! 

Saving Bison in Yellowstone

Awareness of the need to save the bison began to gain momentum; and congress and park management started a new herd in Yellowstone at the Lamar Valley Buffalo Ranch. Conservation efforts continue today. These days there are approximately 5000 bison in the park where they have lived in balance with their environment since prehistoric times. 

In the last few years, scientists have realized their presence in grasslands affects other species living in these areas. Ungulates like elk, deer, and pronghorn benefit from living alongside bison. This is because of the green wave hypothesis. 

Yellowstone’s Chris Geremia is a bison biologist who might explain the green wave as …the progression of spring green-up from low to high elevations or latitudes — determines where and how fast herbivores migrate. Come spring, many species, like elk, mule deer and bighorn sheep “surf the green wave,” following the delicious siren’s call of new plant growth as it winds its way from the lowlands in the early spring to the mountaintops as the season progresses — or from southern latitudes to northern ones.”(Ecosystem Engineers, Vision Magazine 2020 – Medium) 

Bison Migration & Patterns in Yellowstone

It’s interesting how plant growth inside grazing exclosures is less than areas where bison graze heavily. In the Spring Guide Forum 2021, Chris talks about how bison grazing habits and their migration patterns cause the green wave to happen earlier, grow quicker, and the entire area is more productive than if the thousands of one-ton bison were not there. By eating new grass and returning to eat it again every couple of weeks, they are keeping it at the ideal height and nutrition. Doing this renews the benefits of spring over and over and keeps the grass productive and healthy. They also fertilize with urine and dung, and are picky eaters, preferring grasses over forbs. 

Many animals depend on the green wave to put fat on in the spring. Bison aren’t just creating a better diet for themselves but also for other ungulates and animals in the park. If we think about how far bison and other animals migrate each year we start to realize movement is life in Yellowstone.