It’s probably paranoia, but I thought I saw a mouse watching The Unit with me last night.

There have definitely been mice at Pen-Y-Bryn Quarry.  Giant mice, since Pen-Y-Bryn is a model by Michael Campbell.  It hadn’t occurred to me that their droppings might pass for those of 7mm scale sheep, but then Mr Campbell seems to have a fairly philosophical take on the rodents’ rampage:

The polystyrene forming the hills had been excavated (quarried?) and carried along the track all over the model, and small black droppings littered the hillside (in O gauge they might have passed for scale sheep droppings!). The little blighters had nibbled the rock-face (cork bark), and even tried some of the people and animals (tell-tale flashes of whitemetal!), plus other people, animals, and details were strewn about, flattened by the giant rodents.

I’d recommend running a Relco track cleaner; those things used always to give me a shock, with any luck they might fry a mouse.