I've had something similar happen to me when I was farming. I was laying on my back working on a bob truck in a field, doing fiddly slow work on the brake system, when a fox came under the truck with me! I wasn't moving enough to worry him, and he was checking me out. He split quick when I yelled and banged the wrenches around. When he came under there with me I thought 'rabid' and was pretty alarmed, but I think he was just curious. Weird little critters.