Of all the things a guinea pig could want to chew on, a cagemate's hair should be the last thing on the list, right? But, in one of the weirder twists of guinea pig behavior, it does happen. Delly and Sage, in the rescue's sanctuary, had to be separated because of persistent hair chewing. And, it seems, Roxy and Twilight are also having issues.
Their mom writes: "We purchased two young female guinea pigs in September. One is long haired, the other short. The short haired one is constantly "biting" at the long haired one, pulling out tufts of hair and eating it. Obviously, the long haired piggie isn't fond of this, and does screech, but it does not stop the short haired piggy from doing it. Is this a dominance thing? Should I separate them? When they are separated, they both whistle their discontent for being on their own..."
Such behavior typically is either boredom issues or dominance issues, though other causes -- like lack of other things to chew on, or obsessive-compulsive neuroticism -- can't be ruled out either.
Whatever the cause, this a behavior that should not be allowed to continue for two reasons. First, there's the emotional health of the pig being pestered, and the physical pain of having hair pulled out. Second, there's the physical health of the pig doing the chewing and pulling, because all that hair going into their gastro-intestinal tract is not a good thing.
If one pig's squeaks of pain aren't stopping the other one from chewing and pulling, you're likely looking at a dominance issue. One pig is determined to be alpha pig in the cage, and reminds the roommate so often that the behavior meets all the criteria for harassment and bullying. A guinea pig that isn't meek by nature, or hasn't been "beaten down" by a roommate, has no trouble whipping around on a pest and nipping at them, chattering their teeth in warning, or huffing and stomping. A guinea pig that isn't sticking up for itself needs its humans to intercede.
At minimum, the pigs need to be separated into adjoining cage spaces (such as fastening a couple of grids in the middle of a C&C cage to create partitioned spaces) or into side-by-side cages. This way, they can still visit with each other, but the victim has a break from the harassment and the bully has time to settle down. The hope is that the temporary loss of a roommate will effect a behavior change in the bully (i.e., "Every time I chew on my roommate's hair, I get stuck living by myself...which I hate").
In some cases, the temporary separation won't change behavior and the guinea pigs have to be permanently separated. If this is the case, keeping the pigs in side-by-side cages or adjoining partitions in a large C&C cage will ward off loneliness.
Guinea pigs need things in their cages to keep them entertained, and if they're feeling under-stimulated they'll either sleep all the time or pester each other. They, like rabbits, also need stuff to chew on to keep their teeth from overgrowing. A sufficiently entertained pig is too busy to harass roommates.
Having tunnels to run through can promote chase games (the fun kind) and hide-and-seek, and tunnels like Chubes do double-duty by providing something to run through and gradually tear apart. Having a couple of hay baskets with different kinds of hay provides dietary variety. And a simple paper bag or wrapping paper tube, stuffed with hay or not, can keep guinea pigs entertained for hours. My first trio of pigs spent a year chewing on their wooden hide-a-way house, enlarging the width of the door and the front window.
There are some cases that I'm inclined to believe are nervous habits (like nail biting) that spin out into irrational, uncontrollable neurotic behavior. If the hair chewer is overly anxious and skittish in general, the hair chewing may be a symptom of anxiety. Whether the anxiety is an inherent condition the pig was born with, or was caused by something in a previous home, or is triggered by something in the current household environment (e.g., frequent loud noises, persistent uproar from children at play, etc.) is something that is going to require observation and deduction on the part of the owners.
To be clear, I'm drawing a line of distinction between hair chewing and hair chewing accompanied by pulling. When the line has been crossed into hair pulling, and one pig is squeaking out in pain, then you have an unmistakeable dominance issue playing out. When it's hair chewing, any one of the causes I've written about here could be the root of the behavior, and owners will need to observe and deduce through some process of elimination.
In the case of neurotic behavior, you can try the same strategy of temporary separation as a way of breaking an unhealthy pattern.
Whatever The Cause, The Behavior Is Unhealthy For Both Pigs
Ultimately, your goal is to break the bad behavior and distract the hair chewer's attention with more productive means of entertainment. It's similar to recovering nail biters taking up hobbies like needlework or knitting to keep their hands busy until they get over the urge to bite their fingernails.
In the event, though, that you have a severe case that won't be resolved, don't be afraid to separate the guinea pigs. The greater misery for them would be to remain in this kind of twisted, unhappy existence for the rest of their lives.