Suspected Selective Herbivory of Bioenergy Grasses by Meadow Voles (Microtus pennsylvanicus)

Highly productive native and non-native perennial grasses are being grown for bioenergy purposes in North America, and ecological risks of their large-scale production are being assessed to inform breeding and management practices. Giant Miscanthus (Miscanthus × giganteus) and Switchgrass (Panicum virgatum) were introduced into an old-field habitat in Guelph, Ontario, in 2012. Seedlings of these species suffered severe selective herbivory, being severed at the plant base by an unknown herbivore. We therefore performed a live-trapping survey and mark-recapture analysis of the small mammal community in 2012 to identify the probable herbivore and estimate its population density. Meadow Voles (Microtus pennsylvanicus) were the most abundant herbivore in the area, with an estimated population of 265 individuals/ha, a relatively high density. This and other evidence indicate that Meadow Voles were likely responsible for herbivory of >80% of the transplants. Such herbivory could have a substantial effect on the establishment and survival of these grasses, suggesting that future crop breeding programs and ecological risk assessments should take this into consideration.