Multimodal human and pet cues intensify wildlife fear responses

Fear of humans can drive persistent changes in wildlife behavioural and life-history traits, with cascading effects on entire ecosystems. Human multimodal cues and pet cues may influence such fear, yet no study has tested how wildlife fear responses change when human acoustic cues and pet visual and acoustic cues are added to human visual cues. Filling this gap is important for managing outdoor activities for humans and pets while conserving wildlife. Here, using dogs as a representative pet, we tested the effects of human and dog visual and acoustic cues on fear responses of sika deer (Cervus nippon yesoensis) across an ~800 km2 area in northern Japan, using alert distance (AD) and flight initiation distance (FID). We measured both distances with an approaching surveyor alone and with additional cues. Analyses with 266 observations showed that AD was estimated at 80.0 m with the human visual cue alone, and dog barking increased AD by 18.4 m. FID was estimated at 57.1 m with the human visual cue alone, and the human voice and the dog decoy increased FID by 11.3 m and 8.5 m, respectively. These results demonstrate that both human multimodal cues and pet cues can increase wildlife fear responses, suggesting that dog walking may expose wildlife to concurrent predator-associated cues more consistently than occurs under natural conditions. Our finding that adding human acoustic cues increased FID, contrary to previous studies, suggests that animals may adjust the relative weighting of sensory cues depending on predator species. These findings highlight the importance of considering the combined effects of human and pet cues when managing recreation in sensitive areas, favouring targeted measures over blanket restrictions.