The vocalisations and behaviour of chickens in anticipation of rewards

Abstract

The vocalisations of non-human animals can serve as indicators of motivational or emotional state. The anticipation of rewards activates areas of the brain associated with reward and 'wanting', leading to consummatory behaviour and pleasure. Hence, anticipatory behaviour and vocalisations, prior to consumption of an item, could indicate whether animals are experiencing rewarding environments. This thesis aims to investigate whether domestic chickens Gallus gallus produce specific reward-related vocalisations, and whether they can be understood by humans. It first examines the behaviour of chickens in anticipation of different types of reward. It goes on to characterise the vocalisations made in anticipation of rewards, and explore variations in the acoustic structure of these calls. A playback paradigm is further used to study how other chickens respond to reward-related vocalisations, and whether there is any referential information encoded in these vocalisations. Finally, this project asks whether humans can identify chickens' 'reward' calls, and whether they can perceive the arousal levels or valence represented by these vocalisations.Twelve hens were exposed to a Pavlovian conditioning paradigm, using sound cues to signal the availability of two food rewards (mealworms and the hens' normal food), one non-food reward (a container of dustbathing substrate) and a sound-neutral event (sound cue, no reward). A mutedneutral treatment (no sound cue, no reward) provided a baseline for behavioural and vocal observations. This study revealed that chickens increase their activity levels as a general response to reward. Quantifiable differences in the frequency and duration of goal-directed behaviours indicated that hens ranked the rewards differentially, and appeared to be more motivated to access the dustbathing reward.Hens consistently produced a specific 'reward' call, described elsewhere as a 'food' call, in anticipation of all rewards, including the non-food reward. The cue signalling the dustbathing substrate elicited the highest proportion of these calls, suggesting that this reward induced the most arousal in hens. Variation in the acoustic structure of calls appeared to reflect differences in arousal.The peak frequency of reward calls made in anticipation of the dusty substrate was 45-75 Hz lower (p=0.01) than those made in anticipation of food rewards. This is the first study to reveal that chickens produce a 'reward' call. It also demonstrates that the frequency-related parameters of this call vary according to different contexts.Referential information relating to environmental stimuli, such as a source of food or the presence of a predator, is sometimes encoded in the type, or structural variation, of animal acoustic iii signals. If referential information is encoded in reward calls transmitted by hens, receivers should respond as if they had experienced the stimuli themselves. In this phase of the project, twelve hens were exposed to a playback paradigm using calls recorded from other hens made when antici...

An Interactive Feeder to Induce and Assess Emotions from Vocalisations of Chickens

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