I caught some of my eastern collared lizards (Crotaphytus collaris) in the act of breeding this afternoon when I walked past their terrarium while feeding my lizards.
I keep my eastern collared lizards outdoors year round here in central Virginia in south-facing, raised bed terraria which I designed and built especially for this purpose.
The terrarium here is 6′ long, 3′ wide and 3′ high above the surrounding earth at its highest point. The lizards dig burrows amongst the rocks, into the hill as they would in nature. They hibernate deep inside these burrows during the winter. During the spring, they do a “housecleaning” and improve their “hobbit holes”– soil and pebbles begin to appear outward from the entrances. During the day, they enjoy basking on the rocks in the sunshine.
The air temperature here when I took these photos today was 72 degrees. But the temperature of the rocks sitting on a south facing mound of earth in the sun in my south-facing terrarium was much warmer.
Solar radiation works a little differently outdoors than heat lamps do indoors. Lizards outdoors in real sunshine can use their bodies like a brick, to build and store heat from solar radiation over time.
They have some tricks like changing to a darker color and hugging warm surfaces like stones to heat up as well.
Shortly after they finished mating, I checked the surface temperature of the male collared lizard and took a photo to show that even though it was a bit cool here today, because of my careful terrarium design, he was able to raise his body temperature up to 102 degrees. Warm enough for reproductive behavior!