To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video Movie 3 Recording of typical rattlesnake behavior when pendulum and background exhibited positive thermal contrast (pendulum at 36 °C, background at 30 °C) 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