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In a fascinating study of young pigs, researchers found that pigs that were pushed away when they tried to make physical contact with a handler did NOT show a decrease in their attempts to continue to make contact. However, these pigs DID show an increase in frustration-based behaviors. The potential implications of this finding with regard to how we deal with problem behaviors in pet pigs is significant.

In this study, Repeated Handling of Pigs During Rearing. I. Refusal of Contact by the Handler and Reactivity to Familiar and Unfamiliar Humans, researchers looked at pig behavior in the presence of humans under different handling treatments. The groups of pigs were designated as follows: Human Interaction (HI), Refusal of Contact (RC), and a third control group that received no contact. The pigs in the experiment were 11 week old castrated males and the experiment lasted 40 days. For the pigs in the HI (human interaction) group, the handler tried to encourage physical contact through a predetermined protocol, starting with using voice and progressing to mutual physical contact and play ("Behavioral indications of acceptance were the following: nibbling the handler’s hand (in response to catching of the pig’s rooting disk), shaking its head (in response to catching the pig’s ears), active participation in play (pig catches sleeve and shakes the handler’s arm, pig catches zip of overalls, etc."). For the pigs in the RC (refusal of contact) group, the handler discouraged any physical contact - if the pig made physical contact with his nose, he would be pushed away. If he tried to nibble on coveralls or zippers, he would receive a tap on the nose. As we might expect, the researchers found that over time, the HI pigs increased physical contact (up to 35% of their time) with their handler. More interesting though, is that the researchers also found that the RC pigs maintained the same frequency of attempts at physical contact with their handler over the course of the experiment, even though they were pushed away any time they tried to initiate contact:

"Motivation to interact with the handler was high even for RC pigs. Although these pigs were consistently pushed away whenever they established physical contact with the handler, they persisted in trying to establish contact throughout the experimental period, and as often as HI pigs. Their interest in the handler is further underlined by the fact that, when in the pen half away from the handler, they were oriented toward her as often as HI pigs, and that during locomotion, they oriented more often toward her than HI pigs."

While the frequency of attempts at physical contact by the pigs didn't decrease over time, the researchers did find an INCREASE in frustration-based behaviors by these pigs...

"Compared with HI pigs, RC pigs showed more snout contact with the wall, rubbing, locomotion, and immobility. Pigs of the RC group showed a shift in activities over treatment weeks. Levels of immobility were higher from the first recording day onward and showed a nearly fourfold increase over the treatment period, whereas locomotion and rubbing decreased. Increased levels of these activities compared with HI pigs may be partly explained by an altered time budget, as the pigs were denied continuous contact with the handler. Increased oral activity, locomotion, and immobility have further all been observed in various aversive situations, believed to cause frustration (see above; Vestergaard, 1984; Dantzer et al., 1987; Terlouw et al., 1991; Bishop et al., 1999; Lewis, 1999). The shift toward immobility may be caused by the increasing certainty on the part of the pigs that contact with the handler would not be allowed, resulting in increasing frustration."

What does this study mean for us? There are a couple of really interesting takeaways. Firstly, domestic pigs, by their very nature, tend to seek out humans.  However, piglets don't inherently know appropriate behaviors with people and sometimes bite, jump or otherwise engage too roughly (much like an exuberant puppy). Unfortunately, if we interpret these behaviors as dominance or use punishment to try and correct them, it can seriously affect future behavior. Of course, in this study, the pigs in the RC (refusal of contact) group were pushed away ANY time they attempted to make contact - our pet pigs hopefully would not encounter this level of distance from their owners. But often pet pig owners use these methods, at least in part, to manage behaviors of pigs, and this offers some insight into how pigs respond when presented with this type of treatment. It is also important to note that in the HI group, pigs were not discouraged or punished for nibbling hands or rough play, because these are signs of behavioral acceptance. While we may not want to encourage these specific behaviors in pet pigs, we certainly don't want to discourage pigs that are showing acceptance of us! Especially if we are dealing with a young pig that is curious about people but doesn't understand how to interact properly (nips, jumps or engages in other inappropriate behaviors), it becomes essential to help the pig understand what IS expected of him. Using punishment like pushing him away doesn't teach him what he SHOULD do, and can lead to significant frustration for the pig. Two things of note:
          1- Pigs who get pushed away from their handlers show more behaviors associated with frustration, such as standing immobile, nosing the floor or wall, etc. While this study was relatively short (40 days), frustration behaviors in pigs can shift over time - so if we push our pig away when they behave inappropriately or to show dominance over the course of months to years, it is certainly possible these frustration-based behaviors would intensify or worsen over time.

          2- The more interesting finding of this study is that pushing the pigs away when they made physical contact with the handler DID NOT decrease the attempts at physical contact by the pig! If you push your pig away because he is behaving inappropriately or to show dominance, the pig may well keep attempting to make physical contact, all the while becoming increasingly frustrated and anxious because he doesn't understand why he is being punished. More significantly, if light shoving doesn't discourage the pig, you may escalate to more forceful methods, which in turn can lead to fearful responses by the pig that have the potential to turn into fear-related aggression in the future.
Of course, this doesn’t mean that you need to let your pig make physical contact with you anytime he wants. Boundaries are important for pet pigs, but the single most effective way to manage problems with pet pigs is to prevent the unwanted behaviors from happening in the first place, and short of that, redirecting your pig to a more appropriate behavior or action if you notice him doing something unwanted. You can use a crate, kiddie gates, or put your pig outside if you don’t want him bothering you. If your pig behaves inappropriately when he interacts with you by being too mouthy or pushy, you might use methods like positive reinforcement and negative punishment to help your pig learn the proper way to interact with people (check out the Case Studies page for more information).
​Terlouw, E. , & Porcher, J. (2005). Repeated handling of pigs during rearing. i. refusal of contact by the handler and reactivity to familiar and unfamiliar humans. Journal of Animal Science, 83(7), 1653-1663.
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