Unfailingly, when someone is told that they need to gain dominance over their pig by behaving like another pig, they are told that they must randomly make the pig leave the bed, because this is what another pig would do. It might seem to make sense at first glance… in theory, a dominant pig controls the resources, and so would therefore control whether another pig could sleep in the bed. But what does current research into pig behavior tell us?
In reality, current research tells us that pigs belonging to a herd actually sleep in communal nests (Stolba and Wood-Gush, 1989). While in fact a dominant pig MAY well push another pig away from a food source, pigs that belong to the same herd DON’T seem to kick each other out of the sleeping area. As prey animals, communal nesting is an important adaptation to help provide social support and protection from predators - it doesn’t make sense, from a survival point of view, to randomly make your herd mates leave the nest. You would both be in a more vulnerable state and more prone to being attacked and eaten by a predator. Studies have shown that even in large herds where the pigs form smaller subgroups to forage during the day (which allows easier maintenance of dominance hierarchies), the pigs all return to the same resting area at night. Additionally, these studies show that resting preference locations don’t seem to correlate to social status within the herd – that is, the dominant pigs do not seem to exert ‘dominance’ over the lower ranking pigs in the sleeping area!
“Body weight or gender of Iberian pigs studied, as possible indicators of dominance, did not explain the place for final resting. Resting place was not influenced by pig gender or weight, as was found previously by Turner et al., 2003, and this indicates that resting locations were chosen independently of these attributes. The place for final or night rest could be explained by the existence of preferred resting locations (outside or inside the shelters)…(Rodríguez-Estévez et al., 2010) “
“ In spite of the unlimited space available for segregation, the pigs shared a common resting area inside the shelters and around these in the night enclosure, where the gate remained open. (Rodríguez-Estévez et al., 2010)"
So where does this idea come from?
Perhaps the impression lies in the behavior of artificial social groups of pigs that are set up in close confinement systems, especially on production hog farms. Unfamiliar, unbonded pigs from different groups that are randomly and abruptly thrown together absolutely will chase each other out of the bed. But why would we want to treat our pet pig like an unfamiliar competitor? Moreover, even when two pigs fight after they are first introduced, they almost always settle down and start sleeping in the same area after they have become familiar with one another. As social animals, pigs are biologically hardwired to seek companionship and the security that nesting with herdmates brings.
“Following the introduction of novel individuals into the territory of an established group of pigs housed indoors, a period of integration lasting up to 21 days... During this time, the new individuals locate predominantly in a marginal area of the pen … but by the 5th week of the experiment, full integration had occurred. Similarly, space use was not influenced by pig gender or weight measured up to 3 weeks after mixing. This indicates that resting locations were chosen independently of these recorded attributes (Turner et al., 2003)."
Perhaps the notion also lies in the fact that pigs are indeed noisy, do jostle each other and do sometimes head-swipe each other when they are all settling down for the night. But that’s generally just pig-speak for “Hey! I’m trying to sleep! Quit moving around so much!” You might get annoyed and nudge or sharply tell your spouse to stop jostling the bed, but you certainly wouldn’t randomly get up at night and make your spouse get out of the bed over and over again!
Conversely, if we are to accept that pig behavior and social dominance within a stable social group doesn’t ordinarily involve chasing herd mates out of the nest, and we have a pig that chases us away from the bed, what might this tell us? Unfortunately, it leaves us with this perhaps disconcerting realization: A pig that is chasing a person from the bed probably doesn’t view that person as a herd-mate, and therefore probably isn’t trying to climb any social ladder … consequently; dominance theory wouldn’t make sense in this application. More likely, a pig that aggressively chases someone away from the bed may view that person as a threat and is trying to scare that threatening thing away (and don't forget - if the behavior is happening repeatedly, it IS being reinforced!).
Of course, there are no hard and fast rules about the best ways to manage our pet pigs. There is undoubtedly some logic in behaving like the animal in order to more effectively communicate. But we should be very careful about asserting that something should be done because it’s “what pigs do” when in fact that may very well not be the case.
Rodríguez-Estévez, Vicente, Manuel Sánchez-Rodríguez, Antonio Gustavo Gómez-Castro, and Sandra A Edwards. 2010. Group Sizes and Resting Locations of Free Range Pigs when Grazing in a Natural Environment. Applied Animal Behaviour Science. 127, no. 1: 28-36.
Stolba, A, and Wood-Gush, D. G. M. 1989. The behaviour of pigs in a semi-natural environment. Animal Production, 48, pp 419-425.
Turner, Simon P, Graham W Horgan, and Sandra A Edwards. 2003. Assessment of Sub-grouping Behaviour in Pigs Housed at Different Group Sizes. Applied Animal Behaviour Science. 83, no. 4: 291-302.