Encoding of Emotional Valence in Wild Boar (Sus scrofa) Calls
Division of Animal Welfare, Veterinary Public Health Institute, Vetsuisse Faculty, University of Bern, Länggassstrasse 120, 3012 Bern, Switzerland
Institute of Agricultural Sciences, ETH Zürich, Universitätsstrasse 2, 8092 Zürich, Switzerland
Agroscope, Swiss National Stud Farm, Les longs prés, 1580 Avenches, Switzerland
Animal Husbandry, Albrecht Daniel Thaer-Institut, Faculty of Life Sciences, Humboldt-Universität zu Berlin, Philippstrasse 13, 10115 Berlin, Germany
Authors to whom correspondence should be addressed.
Received: 30 April 2018 / Revised: 30 May 2018 / Accepted: 1 June 2018 / Published: 5 June 2018
Animal welfare today is assessed based on both the physical and mental health of animals. However, measuring animal mental health, which includes emotions (i.e., short-term positive or negative reactions to specific events), remains a challenge. Since animals are known to use vocalizations to communicate their emotions to their peers, knowledge about how the structure of vocalizations changes with emotions could be very useful in order to develop noninvasive indicators for assessing animal welfare under captive conditions. The aim of this study was thus to investigate if the type of calls (i.e., grunt, scream, or squeal) or the acoustic structure of the calls emitted by captive wild boars changed according to the emotions they were experiencing. We found that wild boars used different types of calls in positive and negative situations. We also found that their acoustic structure changed according to the emotions. Indeed, calls produced in positive situations were generally shorter and at lower frequencies than those produced in negative situations. It thus seems that wild boars express their emotional state through their vocalizations. Overall, our study gives us better knowledge about how the emotions of captive wild boars could be assessed, and how this compares to domestic pigs.