Department of Physics, Chemistry and Biology (IFM)

As mentioned in the previous section, pigs showed lower activity levels in foam compared to control if provided a companion in the foam box. This reduced activity in foam was only significant for familiar pairs (p=0.006).

This result indicate that a familiar companion may have been more effective in reducing the pigs' stress response to the foam exposure, than an unfamiliar companion.

Unfamiliar pairs spent more time close to each other (p=0.02) and in contact with each other (p=0.009), than familiar pairs. Agonistic behaviours were recorded only in one (unfamiliar) pair within the observation period. However, two unfamiliar pairs had to be seperated later on before the end of treatment due to fighting.

Why was unfamiliar pairs engaged in more social behaviour?

Were unfamiliar pairs interested in getting to know each other?

More time spent close to and in contact with the unfamiliar pig may have been due to an interest in meeting a new conspecific. As clearly agonistic behaviour were recorded in only one pig pair, it is possible that the social interest was affiliative.

Were unfamiliar pairs about to fight?

Pigs prefer the company of conspecifics and are known to fight if mixed with strangers. Although the level of clearly agonistic behaviours were low during the observation period, the fact that two unfamiliar pairs fought later on suggest that the higher levels of social behaviour in unfamiliar pairs may have been a predisposition to fighting.

Did unfamiliar pairs need or derive more social support from more social contact?

Previous studies indicate that pigs respond to stress by seeking proximity to conspecifics. Also, tactile contact has been found important for social support in piglets. Considering the intensly physical nature of pigs' social behaviour, tactile contact may be important for social support also in older pigs. The higher levels of social contact in unfamiliar pairs could be explained by either 1) a greater need for social proximity for social support to be effective with a stranger, or 2) that unfamiliarity actually favours social support in juvenile pigs in this foam-stunning situation.