I'm sure it's a groundhog/marmot of some subspecies, and the little guy or gal just crawled out on a limb for some juicy forage. They're very good climbers* and probably just wanted a change from the grass on dry land.
*Here's one my Jack Russell, Bentley, treed years ago.
it's interesting that the mushrat and cappibarra are close to the same family as evident by the side shot of the road crosser and being in the RAT family too
Turns out what appears to be a tail in the photograph probably is the animals other arm. My friend believes this might be a beaver. Without the tail it may be hard to confirm! It may be a beaver? I don't think it's a beaver the head is shaped differently and I think the fur is a darker brown. And beavers are generally larger!