Time-lapse camera trapping as an alternative to pitfall trapping for estimating activity of leaf litter arthropods

Pitfall trapping is the standard technique to estimate activity and relative abundance of leaf litter arthropods. Pitfall trapping is not ideal for long-term sampling because it is lethal, labor-intensive, and may have taxonomic sampling biases. We test an alternative sampling method that can be left in place for several months at a time: verticallyplaced time-lapse camera traps that have a short focal distance, enabling identification of small arthropods. We tested the effectiveness of these time-lapse cameras, and quantified escape and avoidance behavior of arthropod orders encountering pitfall traps by placing cameras programed with a range of sampling intervals above pitfalls, to assess numerical, taxonomic, and body size differences in samples collected by the two methods. Cameras programed with 1- or 15-min intervals recorded around twice as many arthropod taxa per day and a third more individuals per day than pitfall traps. Hymenoptera (ants), Embioptera (webspinners), and Blattodea (cockroaches) frequently escaped from pitfalls so were particularly under-sampled by them. The time-lapse camera method effectively samples litter arthropods to collect long-term data. It is standardized, non-lethal, and does not alter the substrate or require frequent visits.