Landing force reveals new form of motion-induced sound camouflage in a wild predator

Abstract

Predator-prey arms races have led to the evolution of remarkable disguise strategies. While the theoretical benefits of predator camouflage are well established, no study has yet been able to quantify its consequences for hunting success. High resolution movement data therefore allowed us to study how barn owls (Tyto alba) conceal their approach when using a sit-and-wait strategy, as well as the power exerted during strikes. We hypothesized that hunting owls would reduce their landing force, and therefore noise, on perches located close to a hunting event. Analyzing 87,957 landings from 163 individuals equipped with GPS and accelerometer tags, we show that landing force predicts hunting success. Landing force also varied with the substrate, being lowest on man-made poles in field boundaries, most likely due to the opportunities for enhanced flight control in open landscapes. The physical environment therefore affects the capacity for sound camouflage, providing an unexpected link between predator-prey interactions and land-use. Finally, hunting strike forces were the highest recorded in any bird, relative to body mass, revealing the remarkable capacity of these predators to modulate their landing force and the range of selective pressures that act on landings. Overall, our results provide the first measurements of landing force in a wild setting revealing a new form of motion-induced sound camouflage, its link to hunting success and hence to fitness.