Ecological Exposure History Shapes Giraffe Vigilance Responses to Anthropogenic Noise: A Multisite Playback Experiment

Anthropogenic noise is an increasingly pervasive environmental stressor for wildlife, yet its behavioral impacts on large mammals remain poorly understood. Across the genus <i>Giraffa,</i> multiple giraffe species face varying degrees of conservation condern under IUCN criteria due to rapid habitat modification and increasing human disturbance, yet the behavioral consequences of anthropogenic noise exposure have not been experimentally tested. Because vigilance is a key anti-predator response in large herbivores and is highly sensitive to disturbance, we used it as a focal metric to assess giraffe reactions to noise. We conducted multisite playback experiments across three reserves in the Free State Province, South Africa, that differed in human-exposure levels. Free-roaming giraffes were presented with three anthropogenic sound stimuli (drone, vehicle, people talking) and a natural control stimulus (ring-necked dove). Vigilance responses were video-recorded, quantified, and analyzed using mixed-effects models. Giraffes at the low-exposure site showed markedly stronger vigilance responses to anthropogenic than to the natural control, whereas responses at high-exposure sites were weaker and less differentiated across stimuli. These site-specific patterns indicate that ecological exposure history modulates giraffe responsiveness to noise. Across the full dataset, anthropogenic sounds consistently elicited stronger vigilance responses than the control stimulus, demonstrating that noise alone, independent of visual cues, can alter natural behavior in free-roaming giraffes. Collectively, these findings highlight the importance of incorporating acoustic disturbance into environmental impact assessments and protected-area management. More broadly, the results contribute to understanding how wildlife perceive and respond to human-generated noise and emphasize the need to integrate soundscape considerations into conservation planning as anthropogenic noise continues to expand across savanna ecosystems.