To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video Movie 1 Recording of 36 °C pendulum swinging in front of 30 °C background recorded with a thermal imaging camera (model FLIR-T62101) placed 30 cm from background (approximating location of test snakes during experimental trials). Cooler snakes respond more strongly to infrared stimuli, but we have no idea why George S. Bakken, Hannes A. Schraft, Robert W. Cattell, Donna B. Tiu, and Rulon W. Clark Journal of Experimental Biology 2018. 221:None-None; doi: 10.1242/jeb.182121 Download Original Video