Herring gulls respond to the acoustic properties of men's voices

Due to ongoing global urbanization, some animals have settled in urban environments and rely increasingly on anthropogenic resources. One such urban adapter is the European herring gull, Larus argentatus, whose presence in towns has led to conflict with humans. Previous research has found gulls perceive men's shouting as a threat. We conducted a playback experiment on wild urban herring gulls in a foraging context to determine whether gulls perceive the difference between men shouting versus speaking the same words at the same volume, and whether those stimuli represented the same level of threat. Gulls reacted similarly to men shouting and speaking, as they flinched at the playback, exhibited vigilance, pecked less at the human food source and left the apparatus sooner than when exposed to robin song. However, gulls differentiated between the acoustic properties of men's vocalizations, as they flew away from men shouting but walked away from men speaking. When attempting to deter gulls from exploiting anthropogenic resources, talking might stop them from foraging, but shouting is more effective at making them flee.