Rapid response of a grassland ecosystem to an experimental manipulation of a keystone rodent and domestic livestock

Abstract

Megaherbivores and small burrowing mammals commonly coexist and play important functional roles in grassland ecosystems worldwide. The interactive effects of these two functional groups of herbivores in shaping the structure and function of grassland ecosystems are poorly understood. In North America's central grasslands, domestic cattle (Bos taurus) have supplanted bison (Bison bison), and now coexist with prairie dogs (Cynomys spp.), a keystone burrowing rodent. Understanding the ecological relationships between cattle and prairie dogs and their independent and interactive effects is essential to understanding the ecology and important conservation issues affecting North American grassland ecosystems. To address these needs, we established a long-term manipulative experiment that separates the independent and interactive effects of prairie dogs and cattle using a 2 x 2 factorial design. Our study is located in the Janos-Casas Grandes region of northwestern Chihuahua, Mexico, which supports one of the largest remaining complexes of black-tailed prairie dogs (C. ludovicianus). Two years of posttreatment data show nearly twofold increases in prairie dog abundance on plots grazed by cattle compared to plots without cattle. This positive effect of cattle on prairie dogs resulted in synergistic impacts when they occurred together. Vegetation height was significantly lower on the plots where both species co-occurred compared to where either or both species was absent. The treatments also significantly affected abundance and composition of other grassland animal species, including grasshoppers and banner-tailed kangaroo rats (Dipodomys spectabilis). Our results demonstrate that two different functional groups of herbivorous mammals, burrowing mammals and domestic cattle, have distinctive and synergistic impacts in shaping the structure and function of grassland ecosystems.

The cascading impacts of livestock grazing in upland ecosystems: a 10‐year experiment

“…Moser and Witmer (2000) found that ungulate grazing in a steppe area also reduced shrub abundance and small mammal diversity, but plant and bird diversity were unaffected. Davidson et al (2010) conducted a 3-year, smallscale replicated experiment, manipulating two grazing species, cattle and prairie dogs Cynomys ludovicianus, in a grassland in Mexico and found variable effects of cattle on rodents, and synergistic effects of cattle and prairie dogs on vegetation structure and invertebrates. In Norway, a large-scale replicated experiment was conducted that manipulated sheep grazing and found variable short-term effects on plants (Austrheim et al 2008), invertebrates (Mysterud et al 2010), birds (Loe et al 2007) and small mammals (Steen et al 2005).…”

Black-Tailed Prairie Dogs, Cattle, and the Conservation of North America’s Arid Grasslands

“…Grasslands are fundamentally shaped by two key functional groups that have co-evolved for thousands of years, namely, large migratory mammalian herbivores and small to medium-sized burrowing herbivorous mammals [7,8]. Both functional groups of herbivores play keystone and/or ecosystem engineering roles and have complementary and interactive effects on grassland ecosystem structure and function [9–12].…”

Effect of Removal of Woody Biomass after Clearcutting and Intercropping Switchgrass (Panicum virgatum) with Loblolly Pine (Pinus taeda) on Rodent Diversity and Populations

“…Abundances of small mammals are influenced by changes in habitat structure, including removal of woody debris [15,16] and cover of grasses [17,18], so biofuels production may affect population dynamics and habitat relationships of rodents. Population abundance can be influenced by changes in habitat structure and quality, and a range of demographic parameters determines population abundance.…”