1. An animal gait analysis system, comprising: a computer configured to determine a shape of at least one animal and position and shape of the animal's feet from a plurality of images whether or not the feet are in contact with the floor, wherein the images are images of a bottom view of the at least one animal through a transparent floor of an arena; and to characterize activity of the animal at least in part based on analysis of the shape of the animal and the position and shape of the feet.