Serious Marmot is quite serious. It's a good thing he's not a lot bigger.

According to the definition I learned, marmots are large ground squirrel in the genus Marmota.  The yellow-bellied marmot lives in the western US, and the hoary marmots are found from Idaho to Alaska.   That genus also includes ground hogs, woodchucks, and prairie dogs, because they are all considered to be large ground squirrels.  Many in this group are noted for standing upright and whistling when there is danger.