Camera trapping for small mammals: the case of a non- native shrew

In recent decades, motion sensor camera traps have revolutionised wildlife monitoring as a cost-effective strategy requiring less time investment than traditional monitoring methods. While medium-to-large body sized mammals are captured at sufficient resolution to permit confident species identifications, small mammal species (mice, voles, and shrews) are difficult to distinguish in conventional camera trap imagery. Since camera traps represent a potential solution for overcoming spatial and temporal constraints of traditional small mammal survey methodologies (live trapping), novel designs have materialised in recent years to adjust camera traps for observing smaller animals. In this research, we further refined an existing design, the Littlewood box, and investigated the optimal bait strategy to maximise small mammal detections in the Northeast of England within the currently known range of the non-native greater white toothed shrew, Crocidura russula . We found no significant difference in the probability of detection of small mammal species by bait type, but there were greater numbers of captures of shrew species at traps baited with mealworms. We conclude that the use of bait is associated with a greater number of captures for all small mammal species observed compared to non-baited traps. Despite the cameras being deployed in the centre of the known range of C. russula in Britain, this species was present at a lower proportion of sites than native small mammals.