I've never seen anything quite like it.
Not on any of the other shoes, just the athletic shoes. I don't know whether she's actually eating the shoelace bits or just gnawing through them, although I did find one shoelace end on the floor this morning. Something to worry about? Any way to stop it, other than storing the shoes out of her reach? It's not like they don't have enough toys, or that they don't like them. More fiber in her diet? Hmm.
She also gnawed through the wire on the Christmas lights that we'd had hanging off the mezzanine (while they were off, fortunately). I knew my instincts were right, that they weren't ready for a tree yet. Maybe in a few years.