It’s September, and the prairie is alive with the hum of pollinators. Yellow-flowered cup plants, wild bergamot, and asters dapple the hills in gold, purple, and white. The wind sends waves through the shoulder-high grass. I’m on an overlook at the Neal Smith National Wildlife Refuge outside of Prairie City, in Jasper County, Iowa. On the opposite hillside, a group of fuzzy brown balls are moving through the grass. These are the bison cows and calves. Much of the year, bulls are too rambunctious, and there is a strict separation between the sexes. This is the time for mothers to nourish and raise their young.