Pigs are very social animals that often use sounds and grunts to communicate.
Now a new study shows that the sounds can tell us how the animals feel.
- These are very smart animals that have complex emotional lives.
Only we humans have had a bit of a hard time interpreting them, says ethologist Linda Marie Hannius, who researches pig welfare at the Swedish University of Agricultural Sciences.
Loud screams and short grunts
An international research group with researchers from eight different countries has followed more than 400 pigs through life and mapped the sounds of the animals in different situations.
The researchers have since been able to interpret the pigs' emotions by studying their heart rate and behavior in combination with the sounds.
When pigs experience positive emotions, they give off short grunts with small variations in volume.
Positive emotions are shown, among other things, by the pigs exploring their surroundings and their ears pointing forward.
It was, for example, when the pigs were allowed to run free and when cubs suckled from their mother that the pigs made the happy sounds.
An emotionally positive situation was also when flock members were reunited after being separated.
In situations where pigs do not feel so well, they instead give off loud screams or prolonged grunts.
Typical signs of negative emotions in pigs are, for example, that they stand still, make a lot of noise or try to escape.
The emotionally negative situations included social isolation, quarrels between pigs, castration and handling before slaughter.
The psychic moon affects the physical
This is the first time researchers have mapped such a large amount of pig sounds from all stages of the pig's life stages, and then been able to translate them into emotions.
According to Linda Marie Hannius, previous studies have revolved around how pigs behave when they are unwell, while the new study also examined how we can know if they are well.
- In the past, there has been a lot of focus on animal health as in "are my animals healthy?", While this study pushes for good animal welfare to also include that they should feel mentally well, says Linda Marie Hannius.
But in addition to the pigs feeling better when they are happy, there are also benefits for pet owners.
- There are, among other things, studies that show that when the animals are well and they are not stressed, their immune system increases, they tolerate more and are not as susceptible to infection.
They feel better even physically if they feel mentally well, says Linda Marie Hannius.
App for pet owners
Using 7,000 audio recordings, researchers have developed an algorithm that can tell us whether a pig is experiencing a positive or negative emotion.
In the future, they hope that the algorithm can be developed in an app that pet owners can use to improve animal husbandry and pig welfare.
- Our animals should not just exist, and they should not just not be in pain.
In fact, they should also feel good in the system we keep them in, says Linda Marie Hannius.