This article is from the WSSF 2014 AFRMA Rat & Mouse Tales news-magazine.
By Karen Robbins
One thing I found to keep
one litter of young male mice together as long as
possible without fighting, was to not give them houses.
Instead I gave them lots of hay and shredded napkins
(they also got toilet paper tubes). This way there were no
houses for one male to claim and defend as his own.