There's a small outbuilding in our yard here in Maine, which the kids used for a playhouse. We sit out there some evenings with glasses of wine--it's like a tiny camp. The front rests on the lawn. The back is firmly attached to trees--the ground slopes down abruptly behind the yard, so being inside and looking out the back is like being in a treehouse.

The back has a large (maybe 4 feet x 5 feet) window opening. A screen is firmly fastened to it from the outside. (A big piece of plywood on hinges gets pulled shut in the fall to keep snow out, and re-opened each spring.)

I just went out to remove and wash fabric items we leave there all summer, and found they'd been chewed up in the past month. Close examination of the screen revealed a horizontal opening--a slash--about 3 feet long. That's how the cloth-chewing critters got in.

I see no evidence of a bear's claw marks on the back of the building (and there's no food inside it). Tree branches are too far away to reach the screen. Perhaps hunters invaded the playhouse and slashed the screen for malicious fun, but nothing else was damaged.

Can a horizontal split like this happen spontaneously in a 35-year-old screen? Just curious.