I caught this male blue belly (Sceloporus occidentalis) sunning on a rotting Oak log at the entrance to the Escondido Canyon Park trail. The role of the blue coloration along the belly has long been believed to be for communication: (1) to tell females you're parasite-free, and/or (2) to recognize & contest other males of the same species! Here's a great paper by Olsson et al. 2013.
