Sorry to dissappoint but it's not squirrels. It's the Oak Leaf Roll Weevil. See this link for the story of it and a couple of other wevils. You will see a picture of the little packets and hear about a parasitic tiny weevil that lays its eggs in the same packet and feeds on the larva of the Roll Weevil.
I discovered those packets for the first time today. They're gorgeous!
I found these neatly rolled leaves all over my terrace and in the empty pots that have been waiting patiently for me to plant my half-dead herbs in them. The area is below a Live Oak tree, which has narrow leaves about 1/2" across. The leaves were folded widthwise apparently while being rolled, so the packages were narrow. The rolls in the picture on the website link are dry; mine were fresh and very pretty. I opened a couple and saw dozens of the evenly spaced, parallel, acutely angled, darkened score lines with little obtuse angles at the ends. These short lines at the angled ends showed the dots made by the beetle proboscis mouth parts. The dots were further apart with each penetration until they trailed off as it ended the scoring process. The eggs must be tiny because I could not see them with the naked eye. The packages looked like those specially rolled young tea leaves that are purported to be rolled by monkeys: I think it is called monkey puzzle tea. I'll take pictures tomorrow, although they might be all dried out by then.
The Constant Gardener (I hope that moniker is not taken)