Answer: In my experience, dayliles or Hemerocallis plants are more likely to be damaged during the winter by voles rather than by chipmunks. The same would be true for the bulb lilies(Lilium). Lilies also are prone to winter damage/death if planted in a poorly drained location. The following web site includes information on both animals and how to protect against them.
I hope this helps you troubleshoot.
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