Life Under the Snow: Camera Trap Videos Capture Year-Round Lemming Activity and Behavior.

Studying Arctic animals in winter is challenging, particularly for cryptic species like lemmings, which live within the snowpack for protection from the cold. Winter reproduction is thought to be a crucial component of their cyclic fluctuations, yet little is known about their winter behavior and demography. Camera traps are widely used to study animal ecology, but none are specifically designed for animal life beneath the snow under harsh conditions. We evaluated the reliability of camera traps specifically designed to study the activity and behavior of lemmings under the snow in the High Arctic. Between 2018 and 2024, we deployed 18 camera traps on Bylot Island, Nunavut, to study the year-round activity of brown and collared lemmings. We collected a total of 5884 lemming videos and 15 ermine videos. The frequency of lemming observations in our camera traps was strongly related to lemming abundances estimated with conventional field methods (live-trapping and winter nest counts), highlighting the suitability of camera traps for evaluating lemming relative abundance. Additionally, videos successfully recorded lemming behavior. Both species spent more time exploring and less time resting during winter compared to summer, possibly to search for suitable refuge and food to meet their energetic demands. We also documented several events of reproductive behavior inside the camera traps, and the observation of juveniles provided information on the timing of winter reproduction. Our camera traps offer a valuable tool for improving our understanding of the mechanisms underlying lemming demographic fluctuations and provide new insights into the broader dynamics of tundra ecosystems.