Yellowstone National Park is home to the nation’s largest herd of buffalo. Five thousand animals graze here according to Bill Hamilton, chairman of the biology department at Washington and Lee University.
“As snow melts and the grass greens up, the animals follow that green up," he explains. "They’re looking for the most nutritious grass, and they’ll chase it up into the high altitude as the snow melts.”
To assure their food supply, the park wants to know as much as possible about how grass grows, so Hamilton and his students make regular trips to Montana and Wyoming.
“We are mostly monitoring what’s going on in the soil with microbes and decomposition of dung and urine and organic matter – how that facilitates the re-growth of grasses after being grazed," Hamilton says.
He’s discovered, among other things, that cutting grass is actually good for the plant.
“When you graze a grass or clip a grass with scissors, the roots leak out carbon, and in doing that stimulates decomposition of organic matter, and it gives a flush of nitrogen that then allows the grass to regrow.”
These findings are especially important as land managers confront climate change.
"There is a lot of dogma about how grazing works, but it hasn’t really been shown, at least in modern times," he says. "We have the added effects of climate change, and the park service is keenly interested in what climate change is going to do to the whole system. We know it’s changing. Last year was a record drought and then they had a 500-year flood."
Hamilton’s latest research team was actually staying in the park when the flood hit. Their house was not damaged, and by the time they realized how serious the situation had been, the greatest danger was past. On the other hand, student Pari Ahmadi still recalls the preceding week when she found herself just ten feet away from a buffalo that could weigh 2,000 pounds.
“We were closer than the average person should be to a buffalo!" she recalls. "But we were with trained professionals who knew how to deal with the bison should anything happen.”
The key, she says, is to move slowly so as not to spark a stampede and to carry bear spray.
The study has, so far, helped to assure the national park system that there’s an adequate supply of grass for a herd of 5,000 bison, and the land could support double that number.
