Multiples???

Maybe a rhetorical question:

Multiple animals are mice.
What are multiple computer devices? Mice or mouses...they are both nouns. Any wordsmith out there?

And why is one deer the same as three deer (not deers). Same goes for beer.

If I have another Beer it might be 1 too many beer's ??

But yesterday I drank six beer..........

.....but, in a brew pub, you might try several different beers.
....Does and bucks are multiple deer.
.....Multiple mice? Pests. But, is only one a 'vermin'?