The use of coniferous seedlings as alternative food to protect red oak (Quercus rubra) from vole girdling

Seedlings of deciduous and coniferous species are easy prey for generalist mammalian herbivores such as meadow voles (Microtus pennsylvanicus Ord.). Among several protection measures available to reduce girdling on seedlings, the use of alternative food is thought to be one promising way of “hiding” valuable seedling species from herbivory. We tested the hypothesis that bark‐use of red oak seedlings (Quercus rubra L.) would be lower when alternative food in terms of less valuable commercial coniferous seedlings was available to voles. Four groups of ten voles each were tested to estimate bark‐use indices on red oak seedlings matched with white pine (Pinus strobus L.), Norway pine (Pinus resinosa Ait.) or white spruce (Picea glauca (Moench) Voss), three coniferous species which are occasionally girdled by voles. Laboratory tests lasted 25 days under standardized rearing conditions of temperature (18–20°C), relative humidity (40–60%) and luminosity (16 hL: 8 hD) with winterized seedlings. Red oak seedlings lost between 56% and 76% of the bark on their trunk diameter, depending on their association with specific coniferous seedlings. Use of bark was significantly higher when red oak was matched with white pine, and lower when red oak alone was offered to voles. Coniferous seedlings did not lose more than 7% of their bark from trunk diameter when matched with red oak. Conifers cannot be used as alternative food resources to protect red oak seedlings against vole damage.