For instance you could have had two sister / brother hamsters grow up together and put one of them in with another cage with
different pee smell and then put it back and they would be in deathmatch mode fighting because they go by scent.
I don't know if the PH - balance of adult
pee is
different than baby
pee, or if the
pee smell seeped into the plastic trash can, or what happened, but suddenly, our master bathroom
smelled horribly, fatally, of piss.