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10 Years After Reintroduction, Bison Counters Take to the Skies

Twice a year, the pilot of a small Super Cub airplane picks me up for aerial surveys over the Sun Prairie region. There, a herd of bison has hit a point in their growth curve that makes me sweat. The 16 animals that arrived on American Prairie Reserve on a rainy night a decade ago have transformed into a herd of hundreds thanks to additional imports from Canada’s Elk Island National Park and an incredible reproduction rate.

From the air, I get a better view of the animals as they spread out across an undulating and surprisingly tricky prairie landscape. (We also track their movements thanks to radio collars on lead females.) Wintertime surveys should be the easiest since the contrast of 2,000-pound animals against white snow gives me a head start. Last year, however, the herd was amassed in two large groups and the red-headed calves sneakily hid among their mothers. I ended up taking a series of photos that had to be printed out in large format and glued together in a collage of fur and feet. It’s not an exact science when you’re trying to sort out shadows and extra legs.

Springtime counts, like the one I just completed, are timed just before new calves are born. Unlike the winter survey, the herd tends to be broken up in smaller groups this time of year as the animals get ready for calving season. Family groups emerge, and I often spot mothers and daughters together as well as groups of females that were imported at the same time. One group really caught my eye this yearthe females from the 2014 bison import from Elk Island were all together with the addition of a single adult female and still-red young calf that must have been born in late fall. Family dynamics are becoming more and more interesting as the herd grows!

The survey starts at the western perimeter and we fly 200 feet above the ground from north to south. When we reach a boundary, the plane loops around and moves over by a half mile for the next sweep. If the terrain is difficult, like around creeks, we’ll zigzag around at quarter mile swaths, all the while keeping a tally of animals in each group.

This year’s count went wellit’s hard to believe that 16 animals have transformed into a herd of 450. And it’s even more exciting to announce that the dozens of calves born since the April survey have now pushed the herd past the 500 mark! By the time the fall count comes around, I’m guessing we’ll pass the 600 mark, too.

It sure feels like we’re heading in the right directionand hopefully carving out a path for others to follow.