Influence of Marmota monax on Vegetation in Hayfields

Examination of vegetation around 29 woodchuck (Marmota monax) burrows in two hayfields in Connecticut revealed that grass biomass decreased, and forb biomass increased, as a function of distance from burrows. In addition, orchard grass (Dactylis glomerata) <2 m from burrows was more lush and exhibited significantly greater levels of crude protein than orchard grass 15 m away. Over an entire field, woodchucks caused an increase in biomass of orchard grass an average of 7.4% and reduced the biomass of alfalfa (Medicago sativa) by 2.5%. Differential selection of orchard grass and alfalfa as food, release of grass from competition with alfalfa, and enhanced levels of nitrogen from feces all were plausible factors responsible for the distance-dependent differences in growth of vegetation.