- The sense of smell affects our emotional life. Odours can reduce stress and depression - this has been shown in humans but also in mice and rats. We know that pigs are intelligent, sentient animals that are far more smell-dependent than we are. Why shouldn't their emotions be affected by odours? says Maria Vilain Rørvang, a senior lecturer at the Swedish University of Agricultural Sciences (SLU) on how domestic animals perceive their environment.
She recently received SEK 4.4 million from the Swedish Research Council for the SmellWell project, which will investigate the link between the sense of smell and emotions in pigs. This is the first time that research has been done on how pigs' emotions and sense of smell are linked.
- It is an important topic for animal welfare. There are hundreds of millions of pigs in pig barns around the world and we know very little about how they perceive, and are affected by, the odours in the barn. It may be that we can easily improve their living environment by changing the odours, says Maria Vilain Rørvang.
Madeleine cakes for pigs
Maria Vilain Rørvang already knows that pigs like to sniff at least some odours over others, thanks to her previous project SmellThis funded by Formas. The results of that project showed that pigs are particularly interested in the scents of ginger, lavender, pine, and blood orange, which they even rolled in the same way as dogs. But also that there was a great individual variation; not all pigs like the same odours.
Now Maria Vilain Rørvang wants to investigate how pigs may associate odours with emotions or affective states of mind and whether they can create odour-based memories.
- It's a bit like Marcel Proust's madeleine cake, but for pigs, says Maria Vilain Rørvang.
But for the pigs, it's not about the cake, but about the odours associated with a positive experience. Pigs like to scratch, so the researchers can use this as an example of a positive experience for pigs. Scratching is then linked to the smell of ginger, for example.
- What happens when the pigs only smell the ginger? Do they get happy, and if so, how happy, and for how long? We want to know! says Maria Vilain Rørvang.
She is seeking answers to these questions by studying both pig behavior and neurobiology, i.e. what happens in the pig's brain when it encounters different odours. This is done using a non-invasive method, where a small electrode is attached to the pig's head.
- This allows us to analyse both the pig's behavioural reactions at the same time as how the brain reacts, to take a comprehensive approach to their sense of smell, the neurobiology of the sense of smell, the link to emotions and welfare, says Maria Vilain Rörvang.
Understanding pig emotions
The work will begin in earnest in early 2025, but before that time Maria Vilain Rørvang will travel to Edinburgh and Scotland's Rural College. There she will interact with neuroscientists and ethologists who are partners in the project.
- When SmellWell is finished, I hope we will understand a lot more about how pigs perceive their environment and what we can do to improve it. We also hope that the results will help us understand the role odours play for other animals and even humans, says Maria Vilain Rørvang.
