We found this fellow beside the trail at Terra Nova Rural Park today. He seemed a bit stunned; at first I thought he was neo-dead. But then he shuffled forward a bit.
What was it? Well, obviously a vole, but then what? I’m certain that if you were a small mammal biologist, you would instantly know what species it was. But if you aren't, well, you're in a world of uncertainty. There are few or no diagnostic features to differentiate among the four or so species found here. Descriptions are based on unhelpfully variable pelage coloration, hind foot length, ear length, and relative tail length, and patterning of the enamel on molar teeth. The length measures overlap widely among species. Let’s see, is the tail 30 to 44 percent of total length, or is it 30 percent or less of total length? Wuh? What if it’s exactly 30 percent?
And how to measure such things on a live, in situ critter?
Is the fur brownish grey or reddish brown, and is the tail mildly two-tone or not?
Well, what struck me first was how small this animal was (based on my experiences with Townsend’s and meadow voles), and how small its eyes and ears were (eyes less than 4 mm in diameter). My first guess is Creeping Vole, Microtus oregoni.
The natural history of the Creeping Vole is not well known. Like other species, it makes surface runs through dense turf. According to Nagorsen (2005:274), “The Creeping Vole evidently makes surface runways in grassy meadows, but they tend to be less conspicuous than those made by the larger Townsend’s Vole. A semi-fossorial rodent, the Creeping Vole constructs shallow tunnels in the soil. Several authorities have reported capturing Creeping Voles in mole tunnels.”
Nagorsen, D.W. 2005. Rodents & Lagomorphs of British Columbia. Royal British Columbia Museum.