Aspen parkland pasture altered by Richardson’s Ground Squirrel (Urocitellus richardsonii Sabine) activity: the good, the bad, and the not so ugly?

Abstract

Although Richardson’s Ground Squirrels (Urocitellus richardsonii) are considered pests throughout their North American range, their impact on forage in Canadian aspen parkland has not been explored. We investigated the effect of Richardson’s Ground Squirrel density on forage quality and plant community composition in an intensely grazed cattle pasture in the aspen parkland region of Manitoba, Canada. We detected no significant differences in forage protein content or legume, grass, and litter biomass among ground squirrel density levels. However, ground squirrel density did influence the abundance of invasive and forage plant species; greater squirrel density reduced the prevalence of Smooth Brome (Bromus inermis Leysser) and Red Clover (Trifolium pratense L.) and increased the abundance of Quackgrass (Elymus repens (L.) Gould) and Black medick (Medicago lupulina L.). Plant community diversity also increased with ground squirrel density. There were no differences in soil bulk density or ammonia content among squirrel density levels; however, soil nitrate content was highest at low ground squirrel density. Changes in available soil nitrogen and relative abundances of forage species on this pasture may affect cattle diet by altering both the availability and quality of forage. Our findings highlight the need for further investigation of the role of Richardson’s Ground Squirrel on rangeland in the aspen parkland region to ascertain the generality of the effects documented in our study. Until such effects and their implications for cattle production are understood, land managers should refrain from exterminating colonies of Richardson’s Ground Squirrel.