How reliable are motion‐triggered camera traps for detecting small mammals and birds in ecological studies?

Abstract

AbstractEcological studies often require observations of animals and their behaviour. Motion‐activated cameras (camera traps) based on passive infrared detection (PIR) are a popular solution for recording animal activity in situations when it is impractical for humans to make sufficient observations. However, the reliability of these cameras for recording smaller vertebrates remains uncertain. We assessed the reliability of two widely used PIR camera traps (Bushnell 119740 and Moultrie 13068) for detecting small vertebrates. Specifically, we tested the effects of (1) camera trap model, (2) camera–subject distance and (3) animal class and size on the probability of detection. Brown rats moving across the ground were detected by the Bushnell camera with >80% probability at camera–subject distances ranging from 60 cm to 2 m, while the Moultrie camera was less efficient at distances >1 m. The probability of the Bushnell camera detecting birds feeding on flowers decreased from c. 80% at distances of 40–60 cm to <10% at 2 m and beyond. Larger birds (>20 g) were more likely to be detected than smaller birds (<15 g). Close‐focusing lenses on the Bushnell camera readily allow identification of individual bird species. These results help to establish guidelines for camera trap selection and placement in ecological studies of small terrestrial mammals and birds.