Does danbooru distinguish these two kinds of rodents?
Mice are small rodents.
Rats are larger vermin and appear in the Chinese sexagenary cycle.
Mouse ears / mouse tail tag is applied to both rodent ears / tail...?

I think there should be a distinction between the two.

That being said, looking under rat there are more then a few mice being tagged as rats or the artists themselves have no idea which is which.

+1 for keeping distinction between mice/rat.

About the ears and tail, I'd think tagging them as mouse's is the natural action.

Vlad_Tepes said:
The artists themselves have no idea which is which.

The artists know, just that Japanese and some other Asian languages do not have that kind of distinction.

rantuyetmai said:

The artists know, just that Japanese and some other Asian languages do not have that kind of distinction.

I meant more in the way some seem to have rat bodies/tail but mouse ears.

why not just use Rodent?

Too general, at least with rat or mouse you have a general idea of what you're getting. Rodent you'll end up with things like squirrels and such.