Road noise causes earlier predator detection and flight response in a free-ranging mammal

Increasing scientific evidence shows that anthropogenic noise can impact behavioral, demographic, and community-level processes across a range of taxa—presenting a serious conservation challenge. Given the direct link between antipredator behavior and fitness, it is important to explore the impacts of noise on vigilance and flight. To do this, we conducted playback experiments to test whether noise distracts wild black-tailed prairie dogs from attending to an approaching predator or whether increased noise exposure led to heightened vigilance and responsiveness. Contrary to the "distracted prey hypothesis," prairie dogs responded at greater distances to the approaching human "predator" and took flight more rapidly in noise than during the quieter control. Greater vigilance is likely to be a function of increased perceived threat as opposed to distraction, enabling the prairie dogs to evade predators sooner. However, there are energetic and potential fitness costs associated with heightened vigilance and flight, including the loss of foraging opportunities. Interestingly, the reactiveness of the prairie dogs to the approaching observer increased over the course of the study, but there was no apparent change in their responses to other humans using the natural area. This may reflect their impressive cognitive abilities that enable discrimination between different predators—even human observers. Our findings emphasize that the complex biological responses to anthropogenic noise are dependent on the biology of the species as well as the acoustic characteristics of the noise source.