In the wild, a social animal like the pig depends upon it’s herd mates for detection and defense against predators, as well as other important social-feedback functions. A lone herd animal in the wild has little chance for survival. While we are quick to acknowledge that pigs are herd animals when we use it to justify dominance theory, for some reason, we forget that the most vital element of herd formation is protection from predators; and that essential knowledge should impact our perception of the behaviors of pigs that are kept individually.
Studies show that many species of livestock, when kept in isolation from their conspecifics, show an increase in frustration-based and aggressive behaviors. However, there actually isn’t solid evidence to support that this is because they then view their handlers as their herd mates or that the aggression is dominance based (remember that dominance is a RANKING of two animals with regard to multiple resources like mates and food). Rather, when a herd animal is kept from members of its own species, the resulting behavior is known as isolation-induced aggression. Some of these problem behaviors are thought to be caused by the lack of feedback from conspecifics regarding appropriate social behavior. This DOESN’T mean that the behavior is related to dominance! More importantly, in an animal that relies on social contact and support from its conspecifics, the lack thereof, and resulting frustration on the animal’s part, can lead to low-levels of chronic arousal and stress and the resulting frustration may then be vented in the form of aggression towards humans and other animals in the household.
It is also important to note that there are few studies, but the current research that we have regarding social isolation in livestock where a human handler acts as a surrogate or herd mate shows that while it might lessen the behavioral responses of isolation induced stress, it DOESN’T reduce the endocrine response to isolation-induced stress. Sorry… while we might like to assume otherwise, our pigs probably know that we aren’t another pig.
So what can we learn from this information? Certainly, we shouldn’t feel guilty if we have a single pig as a pet. Fortunately, pigs tend to be highly adaptable to a variety of situations and many thrive by themselves in the right family and household. However, many pigs, due to both genetic and environmental factors, tend toward being reactive and nervous when kept individually (which can be exacerbated if they have received punishment in the past or are inadequately socialized). For some households, luck-of-the-draw and/or the particular household situation might land us with a single pig that isn’t capable of coping without herd mates. If we misinterpret their defensive-aggression, frustration-based and reactionary behavior as dominance, we may simply make those unwanted behaviors more pronounced as that nervous, fearful pig becomes even more so.
For these pigs, the addition of a herd mate can greatly improve their quality of life, lower their stress levels and might, with little effort, reduce defensive and aggressive behaviors. In other words, this pig can let his guard down and relax, because he no longer has to keep a constant look-out. If we have a single pig that is exhibiting aggressive behaviors, getting him a friend might just be a great thing to do for him. Two pigs really are better than one… just maybe not for the reasons we’ve heard.