Actually now that I think about it....It looks more like a Pika than anything else.
They live in western north america. In places like Colorado. By process of elimination....Degu's on top a bein pretty rare are primarily found in the Andes Mountains, The Marmot is a rock dwelling creature but is too bulky and the ears are too small, Muskrats are aquatic dwelling animals like beavers, and Wombats live on land and burrow or live in hollowed out tree trunks. So unless you were mountain journying in Chile the creature you saw is actually more than likely a Pika. By process of elimination. Your mind can rest easy now hopefully.
Asta!!