Finding the sweet spot in camera trapping: A global synthesis and meta-analysis of minimum sampling effort

Camera traps are one of the most common tools in wildlife and conservation biology. Sampling can document and measure animal presence and activity. Captures can be used to estimate population parameters such as presence, abundance, habitat suitability, and resident species richness of specific populations. Effective camera trapping is relevant to conservation for many reasons. For instance, they can be used to inform pre- and post-restoration efforts, monitor the use of artificial structures by species and assess behaviours like predator–prey interactions. This sampling approach can aid in assessing diversity change, habitat change, pre- and post-restoration efforts, artificial structure effects, species presence, and animal behaviour. We reviewed the literature to collect data and estimate incidence effect size measures for both vertebrate abundance and vertebrate richness to examine the relative efficacy of deploying more camera traps for a given period in different ecosystems. Increasing sampling effort through an increased number of cameras significantly increased net positive abundance detection rates in grasslands and mixed ecosystems. Net richness detection rates in mixed, tropical, deciduous, and grassland ecosystems similarly increased with the number of cameras deployed. The total number of days, however, was not a significant predictor of abundance or richness rates detected in any ecosystem. These findings suggest that deploying relatively more cameras for relatively fewer days provides the most effective estimates of vertebrate abundance and richness for a region.