Is a pig grunt worth a thousand words? Perhaps so. In a new study, an international team of researchers from Denmark, Switzerland, France, Germany, Norway and the Czech Republic have translated pig grunts into emotions. The findings have been published today in Scientific Reports. [link: https://www.nature.com/articles/s41598-022-07174-8]
Using more than 7000 audio recordings of pigs, the researchers designed an algorithm that can decode whether an individual pig is experiencing a positive emotion (‘happy’ or ‘excited’), a negative one (‘scared’ or ‘stressed’) or somewhere in between. The recordings were collected in a wide range of situations encountered by commercial pigs, both positive and negative, from when they are born until their deaths.
Short grunts are ‘happy’ grunts
The researchers recorded pig sounds in both commercial and experimental scenarios, which based on the behavior of the pigs, are either associated with a positive and negative emotion.
The researchers then analyzed the more than 7000 audio recordings to see if there was a pattern in the sounds as a function of the emotions, and if they could discern the positive situations and emotions from the negative ones. As already revealed in previous research, the researchers collected more high-frequency calls (such as screams and squeals) in negative situations. At the same time, low-frequency calls (such as barks and grunts) occurred both in situations where the pigs experienced positive or negative emotions.
"There are clear differences in pig calls when we look at positive and negative situations. In the positive situations, the calls are far shorter, with minor fluctuations in amplitude. Grunts, more specifically, begin high and gradually go lower in frequency. By training an algorithm to recognize these sounds, we can classify 92% of the calls to the correct emotion", explains Elodie Briefer.
Farmers can monitor animal emotions
The study of animal emotions is a relatively new field that has come about over the last 20 years. Today, it is widely accepted that the mental health of livestock is important for their overall well-being. The researchers of the study hope their algorithm might pave the way for a new platform for farmers to keep an eye on their animals' psychological well-being.
- Sixteen researchers from Denmark, Switzerland, France, Germany, Norway and the Czech Republic participated in the study.
- The researchers recorded 7414 sounds from 411 pigs in different scenarios, from birth to death.
- The researchers defined the emotions of pigs based on how they naturally react to various positive and negative external stimuli, and whether stimuli can improve (positive) or threaten (negative) their lives.
- A machine learning algorithm was trained to decode whether pig calls can be classified as a function of positive or negative emotions.
Institute of Behavioural Physiology
Research Institute for Farm Animal Biology (FBN)
Elodie Floriane Mandel-Briefer
Department of Biology
University of Copenhagen
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