In October this year I received my 2.2 Thamnophis sirtalis dorsalis from a German breeder.
After they were in their terrarium for a few days I tried to feed them, but they were not interested. After contacting the breeder he advised me to let them brumate at temperatures between 12 and 15 degrees C. He told me that this species stops eating when the temperatures get beneath 15 degrees C.
Of course I followed this advise, even though the snakes had not eaten a thing since I had them. But they looked well nourished so I expected no problems.
Normally I never place a water bowl in the brumation box, but the adult New Mexico garter snakes of the breeder are most of the brumation period in their water bowl.
I gave them a brumation period of 4 weeks and placed them in my "kitchen terrarium" where the temperature never goes under 15 degrees C. I have never seen them in the water bowl in these four weeks.
They did not start eating immediately, but when I gave them salmon, they seem to be starting up.