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.

​​I wanted to share some particularly interesting research on pigs regarding generalization behaviors. Pigs (and other animals) learn from experiences by either generalizing or by discriminating - generalizing is the ability to learn something in one context and apply it to other situations, discrimination is learning something and only applying it in the narrow context in which it was learned. Often with prey species, generalization is an important ability with regard to fear-responses because it allows the animals to recognize potentially dangerous situations after only a single or very few encounters. If a prey animal narrowly escapes a predator in one context, it is important to be able to generalize out to other contexts so that the prey animal responds appropriately in the future. In this study (Hemsworth et. al.,1994), researchers found that "in situations in which pigs are briefly handled by one of two stockpersons in a predominantly negative manner or in which pigs are briefly handled by stockpersons who differ markedly in the nature of their behaviour towards pigs, pigs are likely to exhibit stimulus generalization as measured by their behavioural responses to humans." In other words,  pigs learn to associate rough handling from their specific handler, and subsequently responded to any humans in the same manner, by practicing avoidance or fearful behaviors. This makes sense, because as a prey species, it is important for pigs to recognize and remember when something unpleasant happens and to be able to apply that knowledge to future situations.  Keep in mind that an aversive is ANYTHING the pig finds unpleasant - WE might know that a light shove or push doesn't actually hurt the pig, but if the pig finds it unpleasant, it IS classified as an aversive.

If we use aversive techniques like dominance theory, the pig is likely to generalize his rough handling out to all people. There is a strong anecdotal correlation between homes that utilize methods of force or intimidation to manage problem behaviors and the presence of reactive behaviors from those pigs towards guests and unfamiliar people in the home. Have these pigs generalized their rough handling and learned that all people are unpredictable, frightening and perhaps dangerous?

(ETA): Interestingly, studies also show that while pigs generalize bad experiences, they tend to behave discrimanatorially with regard to postive experiences (ei they won't immediately associate all people with good things if one person treats them well - I'll be discussing those studies in more depth in a future post). It seems it is very easy to lose a pig's trust, and much much harder to regain it.

​(...or, why pigs are more prone to bite indoors than outside)

Pigs have no interest in, or perception of, real estate.  If instead we mean ‘territory’ when we say pigs are more aggressive indoors than out, this also doesn’t really make sense. A pet pig’s territory would, in fact, be wherever he eats, sleeps and spends his days. This could be inside or outside. If it were actual territorial aggression, there would be no difference in aggression levels between indoor and outdoor pigs—wherever  their home, or territory, is would be the site of the same level of aggression. Pigs don’t magically have some sense that a house is worth more than a yard in terms of resource guarding.  A pig doesn’t go, “oh, well, I live outside, and this lame yard isn’t really worth fighting anyone over. If I was in that HOUSE though, oh man, that is prime real estate and I’d be willing to fight over that…” 

Lets consider instead that you are the pig… a room is essentially a dimly lit, enclosed space (remember that you already have bad eyesight); it’s cramped, there are walls and a ceiling that prevent you from fleeing danger easily; there are obstacles (furniture) all over that you could become entangled in if you tried to flee too (not to mention, if the pig doesn’t have continual access to a doggie door, he KNOWS he is trapped). Now consider that perhaps we have guests over, and now there are a lot of strange, scary people in a tight space in the house, and guess what, everyone wants to visit with the pig, because, "hey, it’s a pig! Living in the house! Haha, awesome!" So now, all these scary people are converging on, and towering over, this pig. This heightens the pigs’ fear response already... now add in that this pig likely has already ruled out flight as a possible means to avoid the scary situation, and that leaves fighting, that is, fear-based aggression—barking, snapping and then possibly biting — as the pig’s only option to deal with this frightening situation.  

So here's where it gets interesting… once the pig snaps or bites, we are told that the pig is trying to show dominance, and so we punish the pig, maybe we even put the pig outside. At a minimum, we have reinforced to the pig that yes, he should have been frightened (he was feeling fearful and then got punished!). On top of that, we have ALSO reinforced to your pig that his fear-based response of snapping and biting got him thrown outside, away from the scary things! Perfect! We might think that we are punishing the pig, but the pig has learned the EXACT opposite lesson! “Biting gets me put outside, AWAY from the scary things! It saved me!”  Next time this pig is in the same situation, he will be quick to use his newfound skill (biting) to achieve his goal of getting moved away from the thing he is afraid of. 

Misinterpreting emotions and behaviors can lead to a lifetime of frustration, fear and misery, both for a pig and his people. If your pig is exhibiting problem behaviors, contact a certified behaviorist to help decode the underlying emotions and to develop a scientifically-sound plan of action to help solve the problem.

Be sure to check out Decoding Problem Behaviors for more information.