Hello. I am trying to determine if/what kind of heating to provide in my outdoor night box. I have an 8-year-old desert tortoise that is spending time outdoors over nights for the first time. He seems totally fine being placed in his night box and ventures out on his own during the day (I'd love for him to go back at night). I'm wondering if he required night time heating. His night enclosure is a modified enclosed chicken coop with timothy hay as a bedding. I am in Southern California so it hardly ever gets *that* cold. If heating is recommended, is a mat the best way to go? Is it safe to use with hay as a substrate?