Yes, but that doesn't really answer my question; do they hibernate?
Are you talking about Japanese Ponds, or water turtles in general?
If left at sub-optimal temps for an extended period, but not at temps cold enough to hibernate, most reptiles will develop health problems.
I seem to be answering my own questions here though, & as I only have the one male, I don't mind experimenting with him (I was hoping someone with experience with this species could answer the question).
I didn't see him, or the RES's for about a week with temps dropping into the 30's (The pond iced over for part of a day), then the other day we had temps close to seventy & I saw him & one RES out basking for a bit. Now it has snowed & the temps are predicted to get into the low 20's - I think he'll do just fine.
I'll post sometime in the future with an update.
Cheers, Max
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"I may be crazy, but ya know... I can rationalize just about anything."