More Cameras, Less Time: Increasing Detectability in Camera Trap Surveys

ABSTRACT

Camera trapping is an increasingly popular method for surveying wildlife, especially for conservation management. Two important considerations in the design of camera surveys are (a) the number of detection units (cameras or camera‐groups) per site and (b) deployment time. The trade‐off between these two factors will likely affect data quality and quantity, but there is little information about their relative influence on species detectability. In this study we investigated the trade‐off between deploying more detection units or extending the length of the sampling period on two frequently assessed variables in camera trapping studies—species richness and detection probability. Camera traps were established along ten transects in the Central Highlands of Victoria, Australia, to target small, medium and large native mammals. We used a bootstrapping procedure to iteratively sample each possible combination of detection units (1–6 camera pairs) and deployment days (1–34). The procedure randomly resampled the data with replacement, repeating the process 1000 times for every combination and calculated (a) the number of species detected and (b) species‐specific daily detection probability at each iteration. Multiple detection units in combination with longer deployment times were necessary to detect a high proportion of species present. Increasing the number of detection units or deployment time (or both) resulted in high overall detection probability for the more detectible species in our study region, but multiple detection units were always needed to achieve high detection probability in a reasonable timeframe (< 50 days) for less detectible species. We found that adding extra detection units provided benefits over and above longer deployment times. These findings will guide decision‐making about the number of cameras and length of deployment required for efficient and effective camera trapping surveys.