Tortoises naturally hibernate in winter. It is usual for them to eat enough during the summer/autumn to survive the winter asleep. I'm not sure what the weather is like in Oregon but if it's cooling down with shorter days, I reckon the tortoise is about to hibernate, in which case it will stop eating. If that's what it is, you should put it in a straw lined cardboard box. Seal the box but make sure it has air-holes in it, and put it in a cool, dry, frost-free place over winter. The tortoise should wake up when the weather starts to warm up a bit and the days start to get longer (probably around March). Do check it every few weeks though from the end of February to see if it has woken up.