Small rodents are a key indicator to understand the effect of rapidly changing winter climate on Arctic tundra ecosystems. However, monitoring rodent populations through the long Arctic winter by means of conventional traps has until now been hampered by snow cover and harsh ambient conditions. Here, we conduct the first extensive assessment of the utility of a newly developed camera trap to study the winter dynamics of small mammals in the low-Arctic tundra of northern Norway. Forty functional cameras were motion-triggered 20172 times between September 2014 and July 2015, mainly by grey-sided voles (Myodes rufocanus SUNDEVALL 1846), tundra voles (Microtus oeconomus PALLAS 1776), Norwegian lemmings (Lemmus lemmus LINNAEUS 1758) and shrews (Sorex spp.). These data proved to be suitable for dynamical modelling of species-specific site occupancy rates. The occupancy rates of all recorded species declined sharply and synchronously at the onset of the winter. This decline happened concurrently with changes in the ambient conditions recorded by time-lapse images of snow and water. Our study demonstrates the potential of subnivean camera traps for elucidating novel aspects of year-round dynamics of Arctic small mammal communities.