What are we missing? How the delay-period setting on camera traps affects mesopredator detection

Abstract

Trigger-delays are often set on camera traps to save labour costs involved with servicing camera traps and reviewing images. However, the effects that delays of various length could have on data quantity and quality are unmeasured. Here, we aimed to assess how varying trigger-delays (5, 10, 30 and 60 min) or using an ‘independent event’ classification (i.e. a series of images taken less than 5 min apart on the same camera trap) affects detection rates and the number of individuals per trigger for feral cats and European red foxes. Using real camera trap images, we simulated trigger-delays of between 5 min and 60 min and compared with the independent events. Trigger-delays caused inaccuracies in detection frequencies of 3.6–22.0% for feral cats and 3.1–24.0% for foxes. Further, 68% of independent events in which two individual foxes were present were reduced to a single fox trigger when implementing a 5-min trigger-delay (n = 65). Using trigger-delays likely reduces accuracy and reliability of data generated for wildlife monitoring programs and could affect the types of observations and analyses able to be made from imagery so obtained.