Exposure to diesel exhaust particles impairs takeoff but not subsequent homing and foraging behavior of workers of the buff-tailed bumblebee Bombus terrestris

Abstract The loss of insect diversity and biomass has been documented in many terrestrial ecosystems. Drivers of this insect decline include climate change, habitat degradation, and pollution. Exposure to airborne particulate matter, such as diesel exhaust particles, may be harmful, especially for insects around urban or industrial areas. Ecotoxicological experiments have shown that chronic oral uptake of diesel exhaust particles can result in higher mortality and changes in the gut microbiome in bumblebees. However, how such effects manifest under natural conditions is still largely unknown, especially effects on foraging activity. Here, we exposed workers of the bumblebee Bombus terrestris to diesel exhaust particles in the field at distances of 380 m and 1100 m from their colony. We measured the time until bumblebees took off, the duration of their homing flight after a one-time exposure, and subsequent foraging activity over 1.5 days, recording the number and duration of the foraging flights in comparison to untreated bumblebees. The treated bumblebees needed significantly longer to start their homing flight, caused by some workers that were even unable to take off vertically from the exposure box and performing extensive grooming behavior. Homing flight duration and the subsequent foraging activity did not differ between treated and control workers. It remains unclear why bumblebees struggled to take off after exposure to diesel exhaust particles. This observation needs further investigation to elucidate whether this behavior is induced by particulate matter in general or related to specific physico-chemical properties of the particles inducing a physiological effect.