Presence of trailers reduces culvert-style trap success in American black bears (Ursus americanus)

Abstract

Live capture is an important tool for wildlife research, conservation, and management as it allows for insight into movement, behavior, demographics, diet, and health of wildlife populations. Live capture is also used for conservation translocations or to remove animals from human-wildlife conflict situations. Improving trapping efficiency is beneficial for ethical considerations of wildlife handling, human safety, and the best use of limited resources. American black bears (Ursus americanus) are often captured using traps. Culvert- and box-style traps are frequently transported using a trailer, and some are affixed to trailers, elevating the trap from the ground. Traps can be set on the ground or on trailers to reduce the set-up and take-down times. Although trap elements such as length, height, and visibility can influence trapping efficiency, it is unknown whether trailer presence influences capture success. We assessed the influence of single-axle trailer presence on capture success of trapping black bears in northeastern Alberta, Canada, during spring 2022 and 2023. We compared capture success between the 2 methods and the influence of trailer presence on age and sex class. Sixty traps were set for a total of 472 trap-nights resulting in 133 captures of 80 individual bears. Traps set with trailers present required, on average, 1.6 times more trap-nights per capture (4.9) than those set without trailers (3.1). When only considering new captures, traps with trailers present required 1.9 times more trap-nights to capture a bear, at 8.5 trap-nights/capture for traps on trailers and 4.5 trap-nights/capture when trailers were absent. Trailer presence reduced the success of overall and initial bear captures but did not influence recapture success or the proportion of captured bear age and sex classes. We conclude that wildlife researchers and managers should consider improving trap efficiency of black bears by removing traps from trailers.