Reviewing hours of trail camera footage from the Clophill Lakes nature reserve in Bedfordshire has turned into a challenging exercise in identification for Nic Wilson. The task involves distinguishing between bank voles and wood mice captured in a series of nine-second clips recorded inside a wooden trap.
Distinguishing Species in the Dark
The footage, provided by wildlife volunteer Stephen Plummer, documents activity within a “mostela trap”—a wooden box equipped with a drainpipe entrance and baited with nuts and seeds. Monitoring the clips, which span from late afternoon until early morning, proved difficult due to the monochrome infrared lighting. After reviewing over 200 clips, the observer began to identify key physical and behavioral differences between the two rodents.
According to the observations, bank voles can be identified by their shorter, stubby tails, lower-set ears, stout snouts, and smaller eyes. Their movement is also distinct; they tend to scuttle with a lower center of gravity, unlike the more scampering nature of wood mice. Stephen Plummer noted that, in his experience, bank voles are generally placid and gentle when handled.
Activity Patterns and Behavior
The camera footage highlights different activity cycles for the two species. While wood mice are primarily nocturnal, bank voles are cathemeral, meaning they are active intermittently throughout both the day and night. This was evident in the recordings, as the voles had already cached the majority of the peanuts provided in the trap by the time the first wood mouse appeared at 7:12 pm.
The footage also captured a brown rat investigating the trap. Although the rat was significantly larger, it belongs to the same family, Muridae, as the wood mouse. The historical classification of the bank vole, once known as Mus glareolus or “gravelly mouse,” and the etymology of the word “vole”—derived from the Norwegian vollmus, meaning “field mouse”—reflect the long-standing confusion between these small mammals.
