Vocalizations in Livestock : Encyclopedia of Livestock Medicine for Large Animal and Poultry Production

Despite their energetic cost, auditory signals are a very efficient communication channel used to share information at a distance or in crowded settings. The latter is particularly relevant to farm animals. As social species, livestock often rely on vocalizations to express their needs or intention of behavior (i.e., motivation) to others. Vocalizations can encode information through the use of specific “vocalisation types,” such as pig “grunts” versus “screams,” which differ both in their acoustic structure and function/context of emission, or through more subtle variation in the acoustic structure (i.e., duration, frequency, or amplitude) of each vocalization (Fig. 1). Since vocalizations in livestock are believed to be mostly innate—despite some small effects of the surrounding environment and conspecifics on their acoustic structure—they are predicted to reflect particularly accurately the emotion of the emitter and hence serve as useful noninvasive indicators of welfare. In addition, since their features are strictly constrained by the anatomy and physiology of the vocal apparatus as well as the way it is operated, vocalizations often also contain cues to other kinds of information that are highly relevant for welfare, including dynamic information, such as health and reproductive status, or more static information, such as physical characteristics and individuality. This entry provides a brief overview of the vocalization types described in the most common livestock species (i.e., their vocal “repertoire”) and corresponding contexts of production, as well as the information that vocalizations have been shown to convey in these animals. Using recently developed techniques such as machine learning algorithms, this information can be automatically extracted and monitored, providing useful welfare monitoring tools, at least for contexts linked to vocal production, which are characterized by mid to high bodily activation (i.e., arousal).