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.
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!