Somebody's sneakin' round my back door

We have a mystery.  The back deck faces north and always has a kind of mossy film.  And, right now acorns are falling on the deck.

Those skid marks are from bottom to top.  Or maybe top to bottom.

Here's what the deck looks like.  Not many acorns left up here, either.

We think it's deer.  Since full grown deer probably have more sense, I wonder if it's one of the three fawns I've seen around with no mother.  That situation comes up over the years, but generally some fawnless older deer takes up with the orphan babies.  I havn't seen these three except alone and I wonder if they're sneaking up.  Two are twins, the last is alone.

In case you wonder what Toby's up to lately--everything: