A huge new mall is being built about 40 minutes north of where we live. The site was formerly home to one of the largest prairie dog towns in the state of Colorado. In order to start construction, the prairie dogs had to go. The colony was poisoned and hundreds of prairie dogs died.
Public response to this mass execution has varied from demonstrations against the cruelty of a prolonged, painful death, to cheers that one more population of pests has been eliminated from the prairie. Some of my friends participated in the demonstrations. Others planned future shopping excursions.
Living in Colorado can be interesting, to say the least. On one hand we have environmentalists drawn to our wilderness. On the other, we have generations of ranchers working hard to make a living in an often inhospitable region.
The former will tell you how prairie dogs are a keystone species of the shortgrass prairie ecosystem; many other species depend on them and their impact on the surrounding grasslands. The cattlemen describe how the rodents compete with the cattle for limited forage, and dig burrows that an expensive steer or horse might step into, breaking a leg.
Of course, they’re both right.
It’s hard enough making a living at ranching. So many things can go wrong. The loss of an animal is a serious setback, and it’s expensive to buy feed to replace grasses and other plants eaten by prairie dogs. Studies have reported a reduction in forage on ground occupied by prairie dog towns ranging from 20% to 100%. It’s not much of a surprise that some ranchers shoot these “varmints” on sight.
And it’s still legal in Colorado to do so. A fact sheet by Colorado State University includes four pages detailing an assortment of ways to kill a prairie dog, from traps and barriers to fumigants and poison baits.
Prairie dogs have another strike against them. They’re highly susceptible to bubonic plague, and humans can be infected if they pick up fleas when walking in a prairie dog town. (Outbreaks may be worsened by human activity—fragmentation of habitat seems to make their towns more likely to be wiped out by disease, and populations are slower to recover.) However, they’re not the only carriers of plague-infected fleas. All mammals are potential carriers. Just this past week, a deer here in Colorado Springs tested positive. Should we shoot all the deer?
So, are prairie dogs all bad? If they cause problems for ranchers and carry dangerous diseases, why not eradicate them all?
Lots of reasons!
Their digging and grazing aerate the soil, reducing compaction and allowing water to soak in instead of running off. Think of prairie dogs as giant, furry earthworms, and you get the idea. Their nitrogen-rich droppings fertilize the soil, resulting in forage that is more nutritious than plants in neighboring areas.
Prairie dog towns provide homes for numerous other species. In fact, one study in Oklahoma documented 89 species of vertebrates associated with prairie dogs—and that’s just vertebrates! The extensive system of burrows may be home to cottontail rabbits, snakes, Burrowing Owls, and the endangered Black-footed Ferret, which dines exclusively on prairie dog. The plump rodents are also eaten by badgers, coyotes, foxes, and various predatory birds including eagles, Ferruginous Hawks, and Prairie Falcons.
Even the bare ground that results from such intensive grazing plays a vital role in prairie ecology. Mountain Plovers (a species that just avoided being listed as endangered) prefer to nest on bare ground. So do other birds. Prairie chickens and grouse choose areas with cropped grass for their leks (the “stage” upon which males perform in hopes of attracting a mate).
In spite of the anecdotal evidence, there’s a noticeable shortage of studies documenting the economic impact of prairie dogs. Now there’s emerging evidence that they may even help ranchers. The CSU fact sheet mentioned above goes on to say:
The role of prairie dogs in reducing available range forage for livestock is unknown. Several factors can influence forage reduction, including geographic location, rainfall, dominant grass species and duration of prairie dog habitation. Recent research suggests a wide range of effects, ranging from 20 to 30 percent less forage to an increase in the percent of grass species preferred by livestock.
As with all aspects of nature, we will do more harm than good if we blindly push forward and wipe out species without understanding their importance in the greater scheme of things. The law of unintended consequences doesn’t make exceptions.