2 mice + 1 mouse = World War 3

Question
  For about a month and half, we've been raising 2 female mice, Tak and Gaz, no future intention or expectations, just companions. Immediately during the second day we noticed Tak took on a very mellow "blah" attitude. She's laid-back and does her own thing. Gaz, on the other hand, is the spark-plug. Exercises on the wheel constantly, always engaged some form of renovation with the stuffing or shredding paper tubes for insulation in the area they sleep in. But, she's also aggressive. We would every so often hear Gaz sniffing Tak's backside or something to that extent and Tak would obviously state her objections vocally and they would skitter and wrestle about, Gaz would chase Tak back and forth until she gave up and left her alone. We really don't see this as an issue.
  Well, today, we introduced Gir into the family, another female mouse. While it would be obvious that by this point Tak and Gaz have grown [almost 3 times bigger than Gir], Gaz is exhibiting that same aggressive behavior towards the newbie.
  We put Gir in the habitat with the other two. Tak came over, lovingly introducing herself, sniffing about and Gir was completely relaxed and at ease. Gaz introduced herself by scratching and nipping at Gir constantly. Almost a form of "I'm bigger than you" attitude. But she is being relentless. Gir's fur always has small tracks of where Gaz tries to grip at her. They'll wrestle violently, squeaks here, squeaks there. Gir backed herself into a corner and hangs out there. Gaz will sometimes come over and push stuffing towards her almost as if she's trying to bury her or create a wall between the two.

  It's 3 hours since we brought Gir home. The other two are sleeping and Gir is enjoying the freedom of the wheel and food and other ammenities without being bullied.
  What I'm fearing is that:
  1] They're obviously going to have different sleep schedules for a bit. Gaz might bully Gir while she's trying to sleep, making Gir overly tired and unable to defend herself.
  2] The bullying might get worse. When Gaz keeps a distance and faces Gir, her tail twitches and slaps at the floor of the habitat, like a cat's tail twitches and stiffens when it's about to attack. But this is REALLY violent slapping.
  3] Tak might not stand up and defend Gir, because she's too mellow and Gaz even bothers her a bit too. At this point, we refer to Gaz as the Schwarzenegger of the bunch, always working out, drinking water, eating, stealing food from the mouths of the others, being greedy overall.


  When you walk into a PetCo. and view the container with the mice, I'm wondering if they all started out that way, aggressive towards one another, violent, nipping, wrestling, until they mellowed out and accepted the existence of the others in "their" area. Even when new mice [smaller mice, obviously] are put into the display area, if it's the same then, just on a bigger scale [as in more bullies picking on the new kids].

  Any light you can shed on this, territorialism, signals and what to watch out for is GREATLY appreciated.

Answer
Dear Kenneth,

When mice get to know each other, they need to establish who the A mouse is (and sometimes the difference between B and C; sometimes not).  This can involve a whole lot of squeaking and chasing for sometimes even weeks.  As long as no one is bleeding, everyone seems able to access food, wheel, and bedding, they sleep in the same nest, and no one is acting very depressed, everything is going great.  They should all be best of friends soon.  

Don't worry about their sleep schedules.  They'll probably all be snuggled together by morning.

In the pet store, the mice have usually all come from the same place.  I'm sure the whole "A-Mouse" concept is more complicated when there are 40 mice from different locations. Sometimes there may be a very aggressive mouse in a group who attacks everyone, or sometimes a very sickly mouse whom everybody attacks, but for the most part they are all enjoying the dormitory setting.

Best of luck and fun to you, Gaz, Tak, and Gir. If you write back, what do their names mean?

squeaks n giggles,

Natasha