chewing on each other

Question
QUESTION: I had three female fancy mice that I got all around the same time from the same tank at a petstore. They got along very well, but recently, after I'd had them for about a year, one (named Stevie) died. Since then, the other two (HoneyBee and Diz) have been chewing on eachother's faces, necks, and shoulders. I'd noticed HoneyBee, who is dominant, doing this a little to the other two before Stevie died, but now the two of them are doing it, and it is much more aggressive. They both have bloody patches and scabs, especially Diz. I thought perhaps I had reduced their food too much after Stevie died and they were hungry and irritable, so I increased it, which seems to have helped a little, but not entirely. I have an antibiotic from a petstore that I put on them, but I'm wondering if i should do more. I have an extra tank, but I'd rather not separate them since they've been together pretty much all their lives, and they are so old. I've known older animals to die of loneliness once separated, and I don't want to do that to them. What do you suggest?

ANSWER: Hi Rachel,

This behavior is called barbering, and usually isn't done quite as violently.  The fact that their friend died may have upset the order of dominance, and now HoneyBee is trying to make sure she's still the boss.  It could settle out eventually, but since they are fighting quite seriously here are a few things you could try to space it out a bit:

First, dominance is increased when resources are low, so giving them extra food was a great idea.  Second, adding extra hiding places, so that HoneyBee can claim one and Diz can claim another (or hide) might help decrease encounters.  You could also separate them for only a short while to heal in tanks right next to each other, interchanging bedding so that they can still smell the other mouse, and then reintroduce them in a while (but the barbering and aggression might start up again until they settle on a status quo).  This is probably your best option - as they are already causing injuries to each other and need to heal up.  Definitely continue using the antibiotic ointment on their scabs and wounds, as you are keeping off infection that could make things a lot worse.

The last thing you could try is bringing in a third mouse to spread out the dominance, but this should be your last resort.  If you do decide to get them a third friend, make sure you find the healthiest you can and isolate it by itself for 2-3 weeks to make sure it doesn't bring a parasite to your older mice.  Then you could introduce all three of them at once, and it will probably take them a couple of days to adjust but it might be a little better.  I wouldn't recommend this, though, as it could just as easily make things worse, especially if the new girl doesn't play well with others.

Best of luck!
-Tam

---------- FOLLOW-UP ----------

QUESTION: Hello!
I separated my girls, placing them so that they can see eachother through the glass and putting some used bedding from the old tank into the new one that HoneyBee is now in. But now I have noticed that they don't seem nearly as active. They both mostly just sleep in the furthest corners from eachother. On the other hand, HoneyBee was pretty active throughout last night, rearranging her new home. It's mostly Diz I am worried about. She is in the tank with the wheel (since I only have one) and I haven't seen her running on it at all, which is unlike her. Should I be worried? Are they depressed due to being separated, or is it more likely that they are happy and Diz is finally relaxed now that she doesn't have to worry about being attacked?

Answer
Hi again,

Hmm, that's no good.  It could be that Diz isn't feeling good due to her injuries, but a lack of activity is definitely something to be concerned about.  Was she running on the wheel when HoneyBee was still with her?  I want to tell you to try re-introducing them again because she does sound very lonely and sad, but I'm worried that Diz is in no state to take any more bullying.  Make sure she gets lots of nesting material, food, and water so she can beef up her immune system a bit, and make sure none of her scabs from before look infected or dirty.  It could very well be that they are very lonely now, so if you think Diz can take it health-wise, I would try putting them back together in a cleaned out and rearranged cage with lots of supervision.  Injured mice need to heal...but depression is a serious problem, and Diz has already lost one friend.  :(

If you do reintroduce them, now that they've had a break from each other, you can also try hiding food bits and treats in the bedding in and around each hiding hole so that no matter where Diz hides, she has something to dig around for and munch on.

Let me know how she handles it, and what you decide to do.  My thoughts are with them!
-Tam