Science Spotlight: How to Map a Prairie Dog Town

The Approach

The sun has cooked the hardpan into hot white concrete underfoot and shimmers in the morning heat. As we walk, volunteers’ boots succumb to the dryness and the soles peel off and start flapping. But we’re almost there; ahead of us rises a broad grassy mound, incongruously green in this arid landscape. It’s big, maybe half a mile wide, and studded with industriously constructed little dirt mounds. On most of the mounds we can see one or two prairie dogs, pot-bellied and sand-colored, sitting upright, watching our approach. We cross some invisible line and the nearest prairie dogs start barking an alarm call, which quickly spreads across most of the town. This yipping follows us until we find our stopping point and settle down to work.

The Work

In recent weeks, the Adventure Scientists Landmark crew has been scoping and mapping American Prairie Reserve’s prairie dog towns. Each town receives the same three-step protocol. On a good day we try to bang out three or four of these. The steps are as follows:

1.) Two to four observers arrange themselves on a vantage point (ideally 300 yards away) overlooking a town. Once there, we sit on folding stools and scan quietly for one hour using binoculars and birding scopes. We’re looking for any of 29 “species of interest” chosen to indicate the health and diversity of a prairie ecosystem. Any SOI that turns up is logged digitally into our database, along with a timestamp, GPS coordinate, and photograph, provided they stay still long enough. 

2.) The borders of the town must then be defined and logged onto a GPS. This requires two people. One starts at an outermost active hole with a GPS tracker in their pocket, and they walk slowly from outer hole to outer hole along the perimeter. Not every prairie dog hole is conveniently obvious, however, so a second worker walks ahead and to the outside of the first, amongst the dilapidated, abandoned holes around the town’s edge. When this second walker finds an active hole, he/she alerts the GPS holder to divert their course to include it. The course of the GPS in the inner worker’s pocket eventually traces a bizarre, amoeba-ish loop. This shape goes into a database and can be compared with its predecessors from previous years.

​3.) Finally, we walk a transect. This is a GPS-predefined line, in this case rectangular, which circumnavigates the town entirely. Depending on the size of the town, these can get up around four miles long. Once again, we are on the lookout for our 29 species of interest, which we record just as in step one.

Protocols hit the rocks a bit when applied to the actual prairie. Starting at about 9 am, the heat rising from the ground in the summer reduces everything beyond about 300 yards to a wavering blur. Is that a burrowing owl or just another prairie dog? Or a fencepost? Furthermore, prairie dogs seem to prefer to build on high ground, such that convenient spots from which to scope are rare. Oftentimes we’re only able to see one slope of their hill; any attempt to gain higher ground brings us too close to the borders, which gets us lustily scolded by a hundred little voices and kind of throws off the wildlife-friendly vibe. 

​Today the scoping is especially tricky, and the prairie unusually hot and windless. It’s a big town and the mapping loop alone takes a few hours. The prairie dogs are cantankerous as ever, haranguing us all the way, and by the time we pack up our scopes and start the two-mile hike back to the car we’re running on fumes. We’re glad it’s over, but finishing a substantial job in the heat is a good feeling, and seeing how the towns grow and move on the GPS is immediately gratifying. We walk out tired but happy. It’s a pleasure to work in this place, heat and grumpy rodents included; every time you walk the prairie you find something new, something few ever get to see. Right now, though, it’s high time to go home. The prairie dogs seem to agree; as the green hill fades into the shimmering heat I see one of the sentries stand tall and stretch his little arms out in front of him like a zombie. Throwing his head back, he lets out a high-pitched trill and falls flat on his face. This is the hilarious “all-clear” call. The big ugly humans are leaving now, and it’s back to business as usual.