Wilds Pips not eating

The wild Pips don't appear to eat the lumber.  I gathered all my wild pips into a room with a few trees in it in hopes they'd stop messing with my storage and possibly produce some dirt as well.  They aren't cramped or overcrowded, yet none have eaten from the trees in the room with them.  Swept out the room to confirm and after a good 20 cycles I haven't seen a drop of dirt in that pen with the door to it locked to prevent dupes from messing with the test.  There are 4 trees growing in said pen and I haven't noticed a change in them either.

I happened to have a small undisturbed pocket with a wild pip in it and a tree and it too doesn't have any dirt on the ground.

I don't know if it's just such a small amount that it isn't showing or if it's some other issue.  I saw a wild pipsqueak eat off a branch, but I've yet to see an adult do that.