Equine Behavioural and Physiological Responses to Auditory Stimuli in the Presence and Absence of Noise-Damping Ear Covers

SIMPLE SUMMARY: Auditory perception is a key driver in behavioural and physiological responses and as prey species, horses have evolved to identify these stimuli and respond appropriately to maximise chances of survival. Sport horses are required to perform without distraction by external, irrelevant auditory stimuli and to help achieve this, ‘noise-damping’ ear covers have been developed. This study investigated behavioural and physiological (heart rate) responses of horses to different sounds commonly present in a competition environment and compared these responses in the presence and absence of ear covers. A difference in both physiological and behavioural responses to different auditory stimuli was found, suggesting an ability to discriminate the sounds and alter responses based on the individual stimulus. An overall difference in both physiological and behavioural responses with and without ear covers was also found with a reduction in responsiveness when wearing ear covers, although responses varied between sounds presented. The attenuation of these responses when wearing ear covers implies a reduced perception of sounds with varying levels of effectiveness. We suggest this information can be used to predict responses of sport horses, enhancing management and optimisation of performance while improving horse welfare. ABSTRACT: Despite numerous studies investigating responses to visual perception, there is limited research into how horses respond to different auditory stimuli. Although ‘noise-damping’ ear covers are frequently used on sport horses to minimise distraction from external auditory stimuli, the effectiveness of ear covers has not been established. This study aimed to (i) investigate the responses of horses to different sounds commonly present in a competition environment, and (ii) compare these responses in the presence and absence of ear covers. A total of 18 horses were presented with 5 sounds commonly heard in competition or stable environments both with and without ear covers, in a randomised order crossover design. Behavioural and heart rate responses were recorded. Responses were compared between sounds and with/without ear covers. Differences in physiological and behavioural responses to different complex auditory stimuli were shown. An overall difference in physiological and behavioural responses with and without ear covers was detected, although the only difference in heart rate between ear covers and no ear covers that individually achieved significance was the feed sound. These findings suggest that horses can discriminate sounds and alter their responses based on the individual stimulus, and these responses are reduced when wearing ear covers with varying effectiveness for different sounds.