Lizards' response to the sound of fire is modified by fire history

Many animals survive wildfires; however, the mechanisms used to detect and respond to fire have been poorly studied. Sensory cues like sight and sound are used to recognize threats (e.g. predators) and elicit escape responses in prey. Similarly, these cues might be used to detect an approaching wildfire. We tested whether the western fence lizard, Sceloporus occidentalis, responds to the sound of fire as a threat. We predicted that lizards living in burned areas would be more sensitive to the sound of fire than lizards in adjacent and urban areas, where fire suppression could have induced relaxed selection on fire responsiveness. We compared the behaviours of lizards following an experimental playback where we broadcast the sound of fire along with other control sounds (a predator, a common nonpredatory bird and a novel nonpredatory bird). We conducted our playbacks in 2019 in recently burned areas (using the survivors from the 2018 Woolsey Fire, southern California, U.S.A.), unburned adjacent areas and urban areas. We found that in burned areas, lizards responded more to the sound of fire than all three controls, but in urban areas, they responded more to both the sound of a predator and the sound of fire. Our results suggest that lizard responses to fire sounds are greater in an area that has recently experienced a wildfire than in an unburned area, and that urban areas create a complex evolutionary landscape that also increased antipredator behaviour for other biologically relevant stimuli.