Competition for range herbage between black-tailed prairie dogs (Cynomys ludovicianus) and steers was evaluated in terms of the effects prairie dogs have on herbage availability and use, and steer weight gains. Pastures grazed only by steers were termed control pastures and pastures grazed by prairie dogs and steers were designated treatment pastures. Small mammals and arthropods were monitored to determine if prairie dogs influence populations of these animals. Prairie dogs decreased herbage availability, which apparently led to reduced utilization by cattle during 1977 and 1978. The influence of prairie dogs on the herbage crop did not cause a statistically significant reduction in steer weight gains. However, the lower weight gains of treatment steers amounted to market values of $14-$24/steer less than control steers. The presence of prairie dogs appears to improve herbage quality, thus partially compensating the reduction in herbage available to steers. Pastures containing prairie dogs also supported a greater biomass of small mammals. Arthropod (mainly grasshopper) biomass in August was more than three times higher in control pastures than in treatment pastures.
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