Mass and Energy of Detritus Clipped from Grassland Vegetation by the Cotton Rat (Sigmodon hispidus)

Abstract

Piles of vegetational clippings made by Sigmodon hispidus in a remnant grassland area were collected and analyzed for vegetational composition, dry weight, and caloric content. Population densities of S. hispidus were estimated monthly and correlated with the number of clipped piles of vegetation collected each month. During the 1-year study period, Sigmodon clipped 315.1 kilograms of vegetation on the 4.85-hectare study area. This amounted to 136.1 × 104 kilocalories. Grasses (mainly Andropogon gerardi, A. scoparius , and Bouteloua curtipendula ) accounted for 54 per cent of the vegetation clipped, Ambrosia psilostachya and Kochia scoparia 40 per cent, and Helianthus annum 6 per cent. Seventy-two per cent of the clippings occurred from September to November. The amount of clipped material per rat per month varied from zero in May to 1.3 kilograms in October. The amount of material clipped may not be dependent solely on the density or activity of S. hispidus , but possibly also on the condition of the vegetation. Of the net primary production in this area during the study period, 0.4 per cent was clipped by S. hispidus .