Setting: Central Idaho, summer 2008
1. Who made these?
Pocket Gopher, based on the range maps in Peterson's Mammals, probably northern pocket gopher (Thomomys talpoides).
2. What are they (and how were they made)?
Possom59 got it right in the comments. These are eskers formed when the gopher makes tunnels in the snow and then back fills them to get rid of the the dirt from its underground tunnelling.
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