Scientists translate grunt of the litter to reveal pigs’ emotions

FEW creatures look happier than a pig in muck, but now scientists have proven that, if you listen closely, you can hear how happy they are.

Pig grunts and squeals have been decoded for the first time, in a breakthrough that could help farmers listen out for when their animals are fighting, hungry or being crushed.

Researchers made 7,414 sound recordings from 411 pigs when they were involved in activities such as nursing their young, huddling together or investigating an unusual object. They then designed an algorithm to decode the noises and found that their sounds changed consistently depending on what was going on, with happy and excited pigs tending to make short confident noises, while scared or stressed pigs made longer and shakier sounds.

Running and being reunited with their mother produced the shortest most contented sounds, while physical restraint or waiting in the slaughterhouse changed their cries to a long, rattling blare.

It is the first study in the world to translate the squeals and grunts of pigs into emotions, and researchers hope the algorithm can be turned into a computer program that farmers can use to monitor the welfare of stock.

“With this study, we demonstrate that animal sounds provide great insight into their emotions. We also prove that an algorithm can be used to decode and understand the emotions of pigs, which is an important step towards improved animal welfare for livestock,” says Elodie Briefer, of the University of Copenhagen’s department of biology, who co-led the study.

“Our findings could be implemented in a tool that could record groups of pigs and warn the farmer when a certain threshold of negative calls has been reached, allowing the farmer to go check on the group of animals, for example, during crushing.

“Farmers could also use this tool to know if changes they implemented in the barn results in good welfare for the animals.”

To decode the grunts and squeals, researchers recorded the animals in situations that they judged to be either positive, or negative, for the pigs.

Positive situations were defined as something that improved their lives, such as huddling with litter mates, reunion with the mother, freely running, and enrichment with toys or snacks.

Negative situations were defined as something that threatened their lives, such as not being nursed by their mother, social isolation, fights, castration and waiting in the slaughterhouse. The team believes that the system could be used to better understand the emotions of other mammals.

The research was published in Scientific Reports.