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Snout of character

The Research Leaders 2025 project PIGSMELL is investigating how pigs communicate using their senses and how their positive interactions can ultimately support social stability and improve their health.

Interaction through sense of smell is the main way in which pigs interact with their environment, including social interaction between pigs

Domesticated animals are gregarious in nature, so social environment has a substantial impact on their welfare. Most farm animals are group-housed, and negative social interactions are partly due to the constraints of housing environments and management practices, which can then lead to welfare problems. A plethora of literature has focused on minimising the consequences of negative social interactions, says Jen-Yun Chou, a Marie Skłodowska-Curie Postdoctoral Fellow and part of Research Leaders 2025. “In pigs, for example, excessive aggression is usually caused by constant regrouping practices and the lack of sufficient space to display avoidance behaviour,” suggests Jen-Yun. “This is shown to cause injuries and stress for pigs and reduce their performance. In contrast, we have limited knowledge of what constitutes positive social interactions for pigs.”

Project PIGSMELL is focused on maintaining social stability, which could be key to improving pigs’ health, welfare and performance. Part of the Research Leaders 2025 programme, Project PIGSMELL brings together researchers from Teagasc, Research Institute in Semiochemistry and Applied Ethology (France) and the University of Veterinary Medicine Vienna (Austria).

Nosing behaviour: how pigs communicate

Pigs communicate through visual, vocal and olfactory (sense of smell) sensory cues. Compared to vocalisation, olfaction in pigs is a less understood sensory modality, even though it is their main tool to interact with their environment and conspecifics. Pigs’ olfactory ability outperforms that of numerous other animal species, including dogs. Nosing – the use of the snout in direct or close contact with a subject – is a complex behaviour that needs to be dissected in order to better understand how pigs communicate socially. This is the main focus of this project.

Different metrics, same conclusions?

A range of social metrics are used to analyse pigs’ social grouping. Research on dominance hierarchy in pigs started in the 1970s and remains the main conceptual framework to understand pigs’ social structure.

A clear dominance relationship may be vital to a healthy group as it prevents aggression and increases consolation behaviour, and thus reduces stress; however, little is known about the establishment and stability of hierarchical ranks and the effect of rank position on an individual pig’s welfare. More recently, Social Network Analysis (SNA) has emerged as a new conceptual toolkit applied in farm animal studies. It describes an animal’s position in relation to the rest of the group. “Using contact patterns between pairs within a group of animals, a set of computational metrics calculates the strengths and directions of social interactions,” explains Jen-Yun. “This produces a dynamic and relational picture of social structure. “In addition, the concept of social preference is even less understood. Pigs show preferences for specific individuals, but husbandry practices, such as cross-fostering of piglets and regrouping, reduces the display of preferences. How this may influence their positive social interactions remains unknown.”

Project PIGSMELL therefore explores pigs’ social activities using these different metrics, namely social hierarchy, social network and social preference.

Promoting social stability

Pigs use olfactory information to communicate, but the role of pheromones in pig communication is not well understood. A synthetic analogue of the Pig Appeasing Pheromone (PAP), a pheromone naturally secreted from the mammary glands of lactating sows, mimics this maternal pheromone. Studies have shown that this type of pheromonal compound can reduce weaning stress in piglets and aggression in older pigs, but its efficacy in promoting stability in social groups and positive social interactions is unknown. This project uses PAP as an external aid to provide stability upon regrouping and reintroduction. “Our aim,” Jen-Yun concludes, “is to investigate whether, in the long run, this intervention can be applied in commercial settings to improve social stability and consequently improve pig welfare and performance.”  


Jen-Yun Chou

Research Leaders 2025 and Marie Skłodowska-Curie Postdoctoral Fellow, Pig Development Department, Teagasc Animal & Grassland Research Centre, Moorepark, Co. Cork.

Jean-Loup Rault
Head of Institute, Professor, The Institute of Animal Welfare Science, University of Veterinary Medicine Vienna, Austria.

Míriam Marcet-Rius
Head of Department, Department of Animal Behaviour and Welfare, Research Institue in Semiochemistry and Applied Ethology, France.

Keelin O’Driscoll
Senior Research Officer, Pig Development Department, Teagasc Animal & Grassland Research Centre, Moorepark, Co. Cork. 

[pic credit] FooTToo/istockphoto.com