Looking For Newspaper Comic Strip With This Animal

I thought it was Gasoline Alley, but it isn’t.

Not Pogo, because there are humans featured as the mains.

It would have been mid-‘80s.

I remember one strip when the human characters were discussing it; they weren’t even sure what it was, but its owner said he just called it a donkey(or a dog).

It resembled a donkey, but it had a tail that ended in a spade shape(like the card suit). It seemed to be way more intelligent than a regular donkey. It was black in the daily strip; I can’t remember what it was in the Sunday color comics.

It wasn’t always in the strip, if I remember correctly.

Thanks in advance.