Knock it off. If you want to play with markers volunteer at the campus daycare center. Darts to the human squirrel who is leaving his nutshells in the library planters. You probably think you're being environmentally conscientious or something. Like those shells are going to bio-degrade and improve the soil.
Shells are trash.
Put them in the garbage cans. Don't make the library staff clean out the planters with your debris. And furthermore, it is exactly this sort of eating in the library that attracts the real rodents. So take it outdoors please. A Great Big Dart to the Bud Light drinkers who left evidence of their afternoon of alcohol consumption on the third floor of the library.