I recall reading something decades ago that said they consume oxygen just like us when they don't have light. They need to keep their metabolism going,
When they have enough light, they do produce lots of oxygen and get all or most of their metabolic energy from light. But MAYBE they also consume some oxygen in the light, and just produce more than they consume. That, I don't know.
But I agree with Ken: a trunk is big and is probably not airtight. The cold would have slowed down their metabolism so they would not have needed much oxygen anyway.
>> It got down in the 20s last night.
I think you were lucky they didn't freeze! Maybe the snow insulated the trunk.
