dead mice.

Question
QUESTION: How long has a mouse been dead, if their eyes turned white?
I had 7 in total. I recently bought two new mice from a petco. I heard really loud squeaking from the cage. The mouse i found looked to be dead before i heard the noise. So were the new trying to kill the next young one?

ANSWER: Hi Donovan,

The eyes are one of the first things to decompose in a dead animal, so it doesn't tell us very much.  The best way to estimate time of death is using rigor mortis - the body will begin to stiffen a few hours after death and will remain rigid until about 48-60 hours (2-2.5 days).  After this point the body will go limp again and start to noticeably decompose.  This is your best way to scale how long the mouse has been dead.

It is possible they were fighting, or simply scuffling.  Female mice may chase and scuffle for the first 2-3 days or less as they get used to a new pecking order, but this should never be violent.  Male mice should NEVER be introduced to each other, and if your new mouse is male, I would separate him immediately - this sort of male-to-male fighting can go from chasing to killing overnight and it would be better to be on the safe side than lose a second pet.

New introductions should always be watched very carefully.  Normal chasing and arguing should never be violent.  Any biting or scratching are calls for immediate separation (you can also check the fur for scabs from bites by blowing backwards on the coat to look for spots/scabs).  Tail rattling (a fast buzzing of the tail against a hard object) and boxing (standing on the back legs and "punching" outward at an offending mouse) are both signs that a mouse is extremely stressed, feeling cornered, and may need to be pulled from the cage before aggression results.

I am so sorry for your loss, and if I can help any further please do let me know.
-Tam

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

QUESTION: Well the mice that were fighting with the rest of the mice i already separated and keeping the two in their own cage. But ever since i got the two newest ones they have fought every other mouse i have. I thought it was only a temporary thing but it continued until recently with the passing of my mouse that i mentioned earlier. So i guess my question is what you possibly make a pair of mice kill other mice? At the time when i found my mouse was dead, they were fighting the next youngest one and after separating them, i have put them together once and the youngest mouse was scared and constantly running from the two.

Answer
In addition to the gender issues I mentioned before (that if any of them are male, they will frequently fight to the death), some mice simply do not get along.  Any signs of violence or aggression should result in separation, and it is unlikely to yield a different result from putting them together again in the future.  The best solution is to go ahead and keep them separated so that they can all live stress-free and healthy.

-Tam