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

Abstract

Ecological 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.

Arboreal camera trapping: a reliable tool to monitor plant‐frugivore interactions in the trees on large scales

“…Another challenge is that most bird species are relatively small in body size in comparison to medium or large‐bodied mammals, for which the cameras are designed. For this reason, they may not always be detected by the cameras or even the image reviewers (Ortmann & Johnson, 2021). Nevertheless, camera trapping is still cost‐effective and preferred in studies in circumstances similar to ours.…”

“…When considering the trade‐off between a large monitoring area within the camera’s field of view (i.e., setting the camera farther from the target tree) and the resolution of the images taken for identification purposes (i.e., setting the camera closer to the target tree), we found the camera performed best when placed approximately two meters from the fruit clusters (Zhu et al., 2021). After we selected an individual target tree, we chose a specific position for arboreal camera placement to optimize the viewing angle (Ortmann & Johnson, 2021).…”

Ecological Drivers of Habitat Use by Meso Mammals in a Miombo Ecosystem in the Issa Valley, Tanzania

“…= 597.05 ± 67.51; range = 49-940; Supplementary Material). We attached CTs to large trees, 30-90 cm above the ground, following recommendations for camera trapping of small-and medium-sized mammals (Rowcliffe and Carbone, 2008;Ortmann and Johnson, 2021). To maximize capture probability, we deployed CTs primarily along forest and woodland trails-commonly utilized by terrestrial vertebrates (Rovero et al, 2010;Cusack et al, 2015).…”

Long‐term camera trapping needed to identify sunbird species that pollinate the endangered South African orchid Satyrium rhodanthum

“…Details of pollinator observations between 2007 and 2013 are provided in Van der Niet et al, (2015). In 2017In and 2021 up to six cameras were deployed for 5-28 days per year during peak flowering in October and November. Cameras were placed 25-60 cm from S. rhodanthum inflorescences, which results in a c. 80% chance that birds will be detected by these cameras (Ortmann & Johnson, 2021).…”

“…In 2017In and 2021 up to six cameras were deployed for 5-28 days per year during peak flowering in October and November. Cameras were placed 25-60 cm from S. rhodanthum inflorescences, which results in a c. 80% chance that birds will be detected by these cameras (Ortmann & Johnson, 2021). Cameras were initially set to record both day and night (24 h).…”