Researchers say they have created a technology tool that uses pig sounds to interpret different emotions the animal is feeling.
The tool is based on thousands of recordings collected from more than 400 pigs throughout their lives.
The scientists developed an algorithm that seeks to identify a series of emotions the animals could be experiencing.
The research may lead to creation of an app that farmers could use to learn the emotional state of animals in an effort to improve their productivity and well-being.
An international team cooperated in the experiments that led to creation of the algorithm.
The team was led by researchers from the University of Copenhagen, ETH Zurich in Switzerland and France's National Research Institute for Agriculture, Food and Environment.
The results recently appeared in a study in the publication Scientific Reports.
Pigs are known for having highly developed vocal skills.
The researchers state in the study that pigs make different noises based on what they are experiencing at the time they make the sounds.
And these sounds can be linked to different emotions.
Emotions are generally caused "by the evaluation that an individual makes of its environmental situation," the study states.
The study centered on more than 7,000 audio recordings of pigs in different situations, from the time they were born until they died.
The recordings were collected in both natural and experimental settings.
The team organized the sounds to link them with different situations and activities the pigs were involved in.
The behavior of the pigs was observed in both positive and negative situations.
Positive situations included when pigs were being fed by the mother or were reunited with family members after being separated.
Negative situations included separations, fights between pigs, castration or being prepared for slaughter.
The researchers also studied the pigs in controlled environments.
During these experiments, some of the pigs were given different foods and objects, while others were not.
Behaviors of the animals were followed and pig sounds were recorded, along with notes on their physical reactions.
The team examined the recorded material and attempted to identify similarities in the sounds linked to different situations and emotions.
The goal was to differentiate positive situations and emotions from negative ones.
The researchers said higher-pitched sounds were usually measured in negative situations, while lower-pitched calls were linked to both positive or negative emotions.
"With this study, we demonstrate that animal sounds provide great insight into their emotions," Associate Professor Elodie Briefer said in a statement.
Briefer, with the University of Copenhagen's Department of Biology, was a lead writer of the study.
"There are clear differences in pig calls when we look at positive or negative situations," Briefer added.
She noted that in positive situations, the sounds were far shorter, with few changes in strength levels.
On the other hand, lower-pitched "grunt" sounds usually began high, but then dropped lower.
By training the algorithm to recognize the sounds in different situations, the team said it was able to identify the correct emotion 92 percent of the time.
Briefer said that with additional data and training, the algorithm can be a valuable tool for helping to improve the emotional health of pigs and other farm animals in the future.
"Now, we need someone who wants to develop the algorithm into an app that farmers can use to improve the welfare of their animals," Briefer said.
I'm Bryan Lynn.