Dietary overlap between prairie dog (Cynomys mexicanus) and beef cattle in a desert rangeland of northern Mexico

The diets of prairie dog (Cynomys mexicanus) and cattle (Charolais cows) in desert grassland of northern Mexico were examined in 1-year study using microhistological analysis of feces. Cattle utilized more (P<0.01) grasses than prairie dogs (86% vs. 68% across seasons). One key forage species in cattle diets was Bouteloua curtipendula, which was eaten in greater (P<0.05) amounts by cattle than prairie dogs in summer and winter. Bouteloua gracilis, consistently appeared in cattle feces in all seasons. With the exception of spring, this grass was two-fold higher (P<0.01) in cattle than prairie dog diets. Prairie dogs consumed 31% forbs compared to 16% for cattle (data across seasons; P<0.05). Due to the low woody plant availability in the pasture, shrub was a negligible dietary constituent of both herbivores. In general, prairie dogs had a greater preference than cattle for forbs. Overall dietary overlap between prairie dog and cattle was 68%, which indicates that large forage competition occurs between prairie dog and cattle in all season. However, the long-term profitability of the ranch where these prairie dogs live, and the steady expansion of prairie dog colonies in this area indicates that controlled livestock grazing can be biologically sustainable, compatible with prairie dogs and economically cost effective.