Why Prairie Dog Towns Support the Whole Shortgrass Plain

The Scene

Mid morning on Thunder Basin National Grassland in northeastern Wyoming, the wind moves over cropped grass and low sagebrush. A black tailed prairie dog stands on the rim of a burrow mound, forepaws tucked, scanning. Behind it the ground is bare and packed hard, ringed by clipped stems no taller than a boot. Another animal is at work in the open, biting off a forb at the base and dragging it aside without eating it. A third barks twice. The colony drops, then resurfaces in ones and twos. Horned larks land on the bare soil between mounds. Off the colony edge, thirty meters away, the vegetation stands taller and shrubbier, and the birds there are different birds.

The Creature

The black tailed prairie dog is a ground dwelling squirrel that lives in dense colonies and spends much of its day cutting vegetation, both for food and for sightlines. Clipping tall plants lets the colony see approaching coyotes and badgers. That habit, repeated across thousands of animals, turns a patch of mixed grass prairie into short, open, heavily disturbed ground with bare soil, fresh regrowth, and a network of burrows below. Researchers call the species a keystone engineer, meaning an animal whose physical work reshapes the conditions other species depend on rather than simply feeding within them. Prairie dogs also live at the mercy of sylvatic plague, a bacterial disease introduced to North America that can erase a colony in a season. The USDA Forest Service tracks their footprint on Thunder Basin closely, partly because black footed ferrets, one of the rarest mammals on the continent, eat almost nothing but prairie dogs and shelter in their burrows.

The Ripple

Change the plant structure and the animal community follows. Duchardt and colleagues traced the cascade through arthropod biomass and into birds, showing that a prairie dog colony does not simply subtract species, it swaps one set for another. Birds that need bare ground and short stubble move in. Birds that need shrubs and standing grass move to the colony edge or beyond it. Burrows shelter other animals, and the black footed ferret depends on the system almost entirely, which is why the Forest Service has tied its ferret planning on Thunder Basin to prairie dog acreage. The catch is that the mosaic moves. Sarah Magle and coauthors found that across the Thunder Basin ecoregion, colony area went through boom and bust cycles over two decades, with only 8 percent of the study area continuously occupied for 8 or more of 15 survey years. A given patch can shift from colony to bare ground to shrub within that span, then get recolonized a short distance away.