Contribution of pits dug by goannas (Varanus gouldii) to the dynamics of banded mulga landscapes in eastern Australia

Abstract

The densities of pits made by goannasVaranus gouldiiwere estimated in the three distinct zones of banded mulga landscapes (erosion slope, interception zone, and mulga grove) in paddocks of a grazing study in north-western New South Wales, Australia. In light and moderately grazed paddocks, soil pits were significantly more abundant in the interception zones (M=119.057 m−2) than in the groves and erosion slopes (M=16.057 m−2). In the overgrazed paddock there were no differences in densities of pits in any of the zones. In the groves and erosion slopes approximately 70-80% of the pits contained litter, seeds, and fruits. However, on the erosion slopes less than 20% of the pits contained litter and seeds. The data support the hypothesis that soil disturbance byVaranuslizards produces a positive feedback mechanism for the viability of the interception zone and the functioning of banded vegetation landscapes.