Here are some optical illusion tracks for you. Which track came first? (You can click on the image for a bigger picture.)
This track came from a muddy spot in the trail near a spring right down the hill from my house. I’m having a hard time identifying them because I can’t tell if the inner toe on the lower track is the inner toe, or if that depression is the pad of the higher foot. Do you see what I mean? So it appears that the lower track has a distinctly H-shaped negative space between the toes and pads, which would make this a huge fox. But of that inner toe is actually the pad from the other foot, then the lower pad is deformed and, therefore, so is the negative space. I can see that the right wall of the lower pad is much steeper and somewhat higher than the edge of the rest of the pad, but I’m not good enough to be able to tell if that’s because of some motion of the foot. I couldn’t see any previous or subsequent tracks, as the muddy spot is pretty small and surrounded by rocks and blackberries.