Exploiting the Winter Trophic Relationship between Weasels (Mustela spp.) and their Microtine Prey as a Survey Method for Weasels in Meadow Ecosystems

Abstract Weasels can be important components of grassland and meadow communities where they influence the dynamics of small mammal populations which, in turn, can be keystone species in these communities. We evaluate a method for detecting and identifying two species of North American mustelines (i.e., Mustela frenata and M. erminea) in mountain meadow systems. It is based on previous knowledge that weasels often co-opt the winter nests of their vole (or lemming) prey and frequently deposit scats there. We exploit this aspect of the predator-prey relationship and describe how, when paired with genetic identification of species from scat, searching after spring melt for weasel scats in winter-constructed vole nests may be an alternative survey method for detecting weasels in meadows. Our work was conducted at the Sagehen Experimental Forest in the Sierra Nevada Mountains. We discovered and examined 90 winter vole nests over four spring seasons, resulting in an average (SD) of 3.31 (1.81) nests found per survey hour per year. From these nests we collected an average of 0.57 (0.37) putative weasel scats per survey hour. Of the seven scats that were verified to be from a weasel, five were from M. frenata and two from M. erminea. This was a proof of concept effort, to which we conclude that searches of vole nests for scat that can be genetically verified as weasel should have a place in the biologist's toolkit. The method is likely to be the most efficient for obtaining a genetic sample for weasels in mountain meadow systems.