Does Indian sand boa fast?

Hello everyone, please let my asking for some advice. Sorry for my bad English.

My Indian sand boa Joe, 1.5 year old, male(probably for his small size), hasn't being eating well since the beginning of September. He is losing appetite, his last male was a small pinky three weeks ago.

It's getting colder and colder in Japan(where i live), temperature in his cage has dropped from 82~90f to 72~87f. It is a little chill at night, so i turn on heat panel to warm him up, it doesn't rise temperature much but creates a warm area where Joe can lay on. He sometimes stay one that area until his entire body are warm to touch...

Hes has being eating well since i bought him this spring, and even become a little "chubby". Now his not eating at all. He does show interests when i offer him thawed mice, lick it aground for quite a while, but eventually left away.

Every thing is not changed in his enclosure beside the temperature.
Places where Indian sand boa lives also have cold seasons during the year, so i doubt that sand boa has habit to fast during cold seasons, and temperature drop in Japan may just triggered Joe to do so? Or I'm simply keeping temperature too low? If Joe is fasting how long will it take? Should i assist feed him?

If anyone familiar with Indian sand boa please give me some advice. I will be very appreciate since there are little information.

Thanks for reading!