Hi Nutz
Thanks for the description of what went on, the more you can write the better, like their sex, age, where they live.
The sort of fights you describe are in my opinion just squabbles. You were careful to mention that neither Chip Chip or Nutz actually bite. Chipmunk are very territorial so even best friends will constantly test and battle each other for top dog postilion. I would like to publish a video of squabling and a real fight, but apart from them moving so quick, I can't film it because when it happens I can't really stand by to film I have to intervene. The consequences of a serious fight can be fatal.
What I think is a serious fight is a swirling mass of fur, when one or both are really biting. They are trying to bite under the throat or more often the back just above the hind legs or the nose. When you break up a fight like this you stand a strong chance of being bitten yourself. But normally just putting your hand between the two of them is enough to stop the fight. I find if they can't see each other because of your hand that's enough. They will seldom move away though, it's all about standing your ground if your a chipmunk. So what I do is pick one of them up and put them on my shoulder and go to another room. Chipmunks are easily distracted, and so long as they have got out of the situation without losing face they can then carry on as normal. It's all a power struggle with them. No matter how tame they are with you they will always be semi wild, and instincts overrule everything.
I have siblings, normally brother and sister pairs, they live together, and always have. But sometimes a power struggle breaks out. You may hear noises as one may become frightened, but it can be all over in a second. As I said this will always happen, I'm afraid you will have to learn the difference, but if ever you think things are continuing and one of them is always intimidated or being picked on then it's probably time to separate them. By separation i mean not only living together but also separate free range times. I learnt my lesson when I let fudge out for her usual free range, went out to make a cup of tea and came back to find her dead. Although I'm not 100% sure, I strongly suspect she was the victim of a power struggle, this time between two girls.
Although i haven't put this on my website, you should know the signs of a really frightened chipmunk. You would have noticed they can sometimes swish their tails in a S shape. More often than not this is because they have discovered something new in their territory and life. They are not afraid but curious and cautious. Look at their whole body, you may notice they are ready to spring away if anything spooks them. The other reasons they are swishing their tails is to warn others, and make themselves look bigger. Check their ears, if flat they are either in danger or at least feel uncomfortable. If a chipmunk is in what it considers a life or death situation it will stand on it's hind legs and look as if it's facing up to it's aggressor. In some ways that's true, the chipmunk feels it has no way out, so it has to fight. It looks like boxing and it's hard for me to describe. But Gilly put a YouTube video of a chipmunk threatened by a cat, this video perfectly demonstrates what I'm on about.
I've rambled on a bit here, but they don't tell you about fights and squabbles in any book on keeping chipmunks. I'm still making guesses here, but my opinions come from watching them for years, but still I could be wrong. I think you did well to stay and watch them, until you think you know what's going on can you leave for a few minutes. Also the more you watch them the more you will understand them.
Now about sex, the books will tell you they won't be thinking about a mate this time of year. I think that's wrong, males are up for it most of the year, but females will announce their interest twice a year, spring and summer. That's what the books say, but I've already had two females spend all day chirping to attract a mate this year. I expect those same females to have a few more days later in the year chirping all day. When your female wants a mate you won't misunderstand what she wants. The chirping goes on all day, and sometimes a little bit the next day. The problem for their owners (us) is that the males know a female is ready before the chirping starts. I think there must be pheromones involved as well as the audio signals.
To sum up, you need to keep an eye on them when you let them out, but I think it's fine for them to be out together. You have given them a new territory to own, and someone needs to be top chipmunk. But until you're sure it's just a pecking order dispute, you need to be there with them all the time on free range. Yes, sex is possible even at this time of year, and don't think you can intervene in time to stop it, because they are quick. Have the male neutered if you don't want them to breed, or let them breed and go on a new adventure. But be prepared if you do breed chipmunks either to have to part with some or build separate aviaries for them all.
