If not stored in sand or sawdust, they indeed will dry and shrivel considerably. Unless they are really small to start with, it's usually not a problem. Those which have short fat tubers are usually able to retain a high percentage of the stored water. Those which have a long skinny tuber will shrivel quicker and I have lost a few of them over the 40 years of growing them. At this point in time, you might also note a tiny bit of new growth developing. If so, I would not worry about it. I've yet to lose one that has showed a winter growth bud.

Martin