Prairie dogs: The eye of the storm?
by Carolyn Nistler and Jim Knight, Extension Wildlife Program, Animal and Range Sciences Department, Montana State University
"The black- tailed prairie dog still is a "candidate" species, one that receives yearly review to determine whether protection is needed.."
Prairie dogs. Love 'em or hate 'em, everyone's got an opinion. Producers often view them as agricultural pests. Conservationists want them protected, and shooters want to, well, shoot them. In the late 1800s and early 1900s, prairie dog populations boomed due to disturbances caused by settlers, such as overgrazing and cropland conversion. Prairie dogs were perceived as pests, and poisoning and shooting campaigns began that lasted throughout much of the 20th Century.
In the 1980s and 1990s, attitudes towards prairie dogs began to shift as preservation of the grassland ecosystem gained importance. This view shifted so much, in fact, that in 1998, the U.S. Fish and Wildlife Service received a petition requesting that the black-tailed prairie dog be protected as a threatened species under the Endangered Species Act. The USFWS found that protection was warranted, but could not be done because other species were in more immediate need of protection. The black- tailed prairie dog still is a "candidate" species, one that receives yearly review to determine whether protection is needed.
How will it affect prairie dog management in Montana? Many Montanans feel that Montana's prairie dog populations are more than healthy, and that the petition to list is a joke. It isn't. The petition suggested that prairie dogs have beneficial or neutral effects on livestock forage. The research supporting these conclusions had been conducted in South Dakota or Colorado, but not Montana. The highest concentrations of prairie dogs in Montana are in Phillips County. When word of the petition hit the street, many producers and managers in north- central Montana questioned the statements made in the petition. Montana State University was contacted, and in cooperation with the Bureau of Land Management and the Montana Department of Fish, Wildlife and Parks, developed a study to quantify the effects of prairie dogs on the vegetation of Montana mixed grass prairies. The objectives of this study were to compare total plant biomass, number of different plant species, ground cover, nutritional differences and shrub dynamics between prairie dog colonies and adjacent uncolonized sites.
During the summers of 2000 and 2001, vegetation was sampled on and adjacent to 40 prairie dog colonies in County. Total standing crop biomass was more than twice great on uncolonized rangeland than within a prairie dog and was dominated by cool-season perennial grasses and sagebrush. Although of little or no value to livestock, is an important habitat requirement of many native prairie-dwelling species. Vegetation within prairie dog colonies was dominated by fringed sagewort, and sagebrush was virtually eliminated. There also was more variety of plant species at uncolonized locations.
Although live herbaceous vegetative cover was similar between colonized and uncolonized sites, bare ground was higher within prairie dog colonies, and litter was greater adjacent rangeland. This is primarily due to prairie dogs clipping vegetation to increase visibility and facilitate movement on their colonies. Due to the clipping, mid-grasses are not allowed to attain their full height colonies, whereas off prairie dog colonies, grasses mature, die, and then become a component on the ground. Further, as is with any grazed area, prairie dog colony plants tended to slightly higher digestibility and crude protein content (1-2 - cent higher) compared to uncolonized, or less heavily grazed rangeland.
It had been suggested that this increase in nutritional content of vegetation on prairie dog colonies would offset decrease in total biomass available on prairie dog colonies. Montana, this does not appear to be true. Although crude protein content of vegetation is slightly higher on a percent on prairie dog colonies, there is more vegetation and a greater amount of total crude protein available on uncolonized rangeland. The decrease in total standing crop biomass may have varying effects on different animal species. This may have detrimental effect on species needing herbaceous cover, such as sage grouse or mule deer. The increase of bare ground is found on prairie dog colonies may have a positive effect animal species that require open spaces with less cover, the mountain plover and burrowing owl. We found that older prairie dog colonies located in the mixed-grass prairie of eastern Montana have less total crop biomass, reduced number of species, and less total protein. These findings contradict those stated in the petition to list the prairie dog as a threatened species.
The impacts of these effects will depend on the goals of land managers. MSU's findings suggest that prairie dog colonies may not be ideal for grazing cattle due to a decrease in total standing crude protein. Unlike other findings that suggest prairie dogs may have beneficial or neutral effects to native rangeland, the MSU study indicates that prairie dogs may have detrimental effects for some species. The unique area created by the presence of prairie dog colonies may have beneficial effects on prairie dogs, mountain plovers, and burrowing owls while having detrimental effects on cattle and sagebrush obligates such as sage grouse.
Now for another complication! Sage grouse have also been petitioned for listing as a threatened species under the Endangered Species Act. How will we manage these rangelands when one potentially threatened species is actively modifying habitat for another potentially threatened species? To answer that question, we will have to battle one heck of a storm.
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