Yellowbelly Marmot Horseshoe Basin, Argentine Pass Area, Summit County, Colorado.
The marmot is a large, nonaggressive woodchuck in the rodent family. It's favorite home is in rock fields of boulders or chunky talus. It feeds on plants but will also scavenge food scraps left behind by careless hikers and campers.
This fellow was quite a "ham". As we approached this area, he popped up from a jumble of rocks and allowed us to get very close for ten minutes of intensively photographing.
When this species is alarmed, it emits a loud, clear whistle, which has given it the local name of "whistle pig".