Age determination of voles (Microtus spp) consumed by barn owls (Tyto alba) based on wear of the occlusal surfaces on individual molars

Meadow voles (Microtus pennsylvanicus, Ord, 1815) are an integral part of the food web as they often bridge the gap between producers and carnivores. Due to their large biomass and the fact that they “feed” everybody else in the ecosystem, we want to understand the age distribution of the meadow vole population. We examined the wear on the occlusal surface on individual molars found in barn owl (Tyto alba) pellets that were collected from nests in a 0.16 km^2 range in central PA. The molars were identified to species by using an ad hoc pictorial atlas made from the Natural History Collection at Susquehanna University. Our preliminary results have revealed that all 590 of the individual molars collected are from Microtus pennsylvanicus. Based on the occlusal wear of all 590 molars, we defined three age classes (i.e. juvenile, adult, and senior) and we sorted samples accordingly. As most of the sampled molars seemed to have medium wear, the most represented age class (76%) corresponded to adult individuals. This may prove useful in future studies where age determination of the prey population will indicate the ages of voles that are available in the surrounding area, or may represent which age classes the owls selected for consumption, providing an indirect way to establish a relative age structure of the voles available for consumption or directly eaten by owls