2:03 PM Clear, sunny, slight breeze, 12C (54F) in the shade
Male #40 was coiled loosely in the grass and partially exposed to the sun next to the log he is sharing with several other rattlesnakes this winter. His core body temperature was 16C (61F) and he immediately uncoiled and disappeared under the log as I approached. (The body temperature is calculated from his transmitter pulse interval.)
All others were cool and out of sight.