Fig. 7. The effects of perches versus tunnels and width on posture of a corn snake (SVL=102 cm, mass=400 g). (A) Horizontal perches of all seven diameters (1.6, 2.9, 4.1, 5.7, 8.9, 15.9 and 21.0 cm). (B) Horizontal tunnels of all seven corresponding widths (5.6, 6.9, 8.1, 9.7, 12.9, 19.9 and 25.0 cm). The shaded areas indicate the regions of static contact with the surface. In the 19.9 and 25.0 cm tunnels, only a single snake moved using concertina locomotion, and in the 25.0 cm tunnel it did so without any crossing regions. All images are for the time within a cycle when the region of static contact is longest. Videos of locomotion described in this paper can be found at http://bioweb.ad.uc.edu/faculty/jayne/videos.htm.