Evaluation of Predator Attendance at Pitfall Traps in Texas

Researchers using drift-fence sampling with associated pitfall traps have analyzed a number of problems associated with this technique. One unquantified problem is the effect foraging vertebrate predators might have on animals captured in pitfall traps. We used Deer Cam® cameras and track-monitoring stations to estimate amount and variety of vertebrate predators attending pitfall arrays in Bastrop and Guadalupe counties, Texas. We recorded 316 photographs of 19 species of vertebrates over 327 camera days among 16 drift-fence arrays. During 1,838 trap nights, we documented 679 individual track sets at track-monitoring stations established on 50 individual pitfall traps and 8 control plots. Ten potential vertebrate predators were documented visiting pitfall arrays with the raccoon (Procyon lotor) being the most frequently recorded species. Statistical analyses indicate that presence of predators at track-monitoring stations or pitfall traps did not influence detectability or capture success of small vertebrates. However, these results could be confounded by the low effect size and reduced power due to low number of animals captured in pitfall traps during the study. Consistent and frequent visits by predators to pitfall traps indicate that risks exist for confined animals and the potential consequences increase for rare or endangered taxa, which potentially could be exposed to higher levels of predation when confined to pitfall traps.