Fig. 2 Infrared thermal images of tegu lizards following prolonged absence of solar heat gain. Infrared thermal images of tegu lizards following prolonged absence of solar heat gain. (A and B) A tegu lizard viewed before emerging from its burrow at first light in the morning (6:00 a.m.) during the reproductive season, demonstrating thermogenesis in an outside burrow (A). On a separate occasion, tegu lizards were imaged (10:00 a.m.) after extensive equilibration in a constant temperature environmental chamber, demonstrating cool skin temperature (B) whereas the core temperature, recovered from implanted data loggers, was much warmer. Glenn J. Tattersall et al. Sci Adv 2016;2:e1500951 Copyright © 2016, The Authors