Nono, the mice are uber-intellects from another dimension. Earth is their billion-year old incubating experiment. They were just about to get their result (the ultimate answer to the meaning of life) but then were really pissed off when the Vorgons destroyed earth to make way for a space superhighway. LOL.
Maybe this was from 'Life, the Universe & Everything'. Someone can look it up on wiki, I suppose.
I hope I'm right (about Tiay's reference) else I'm going to feel pretty silly explaining all this...
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh