An international team of researchers from Denmark, Switzerland, and France has successfully decoded pig grunting! Based on thousands of audio recordings collected throughout the pigs' lives, they translated the sounds into real emotions.
Researchers analyzed over 7,000 audio recordings obtained from 411 pigs and developed an algorithm capable of determining whether a pig is experiencing positive emotions (such as "happiness" or "pleasant excitement"), negative emotions (such as "fear" or "stress"), or something in between. The recordings were made in various conditions that pigs encounter on farms.
Experiment Procedure
Positive emotions were recorded during moments of feeding piglets and reunions with family after separation. Negative situations included separation, fights between piglets, castration, and slaughter. The scientists also created special conditions, such as introducing piglets to toys.
Previous studies have shown that high-frequency sounds (such as squeals) are more likely to occur in negative situations, while low-frequency sounds (such as grunts) can appear in both positive and negative contexts. A more detailed analysis of the audio files allowed for clarification of these connections.
"In positive situations, the sounds are shorter and have slight amplitude fluctuations. Negative grunting starts at a high frequency and gradually decreases. By training the algorithm to recognize these sounds, we can classify 92% of the sounds made by pigs," the authors of the study report.
Additionally, characteristic signs of negative emotions in pigs include immobility, frequent vocalization, and a tendency to escape. Positive emotions are manifested in exploring the environment and pricking their ears forward.
