A colony of marmots was located inside the south entrance of Yellowstone on the east side of the Snake River just south of the junction of Lewis and Snake Rivers. The colony lies in a north-south direction on an old terrace of the Snake River at an elevation of about 6680 feet. The burrows are along the old river bank and in the alluvial flat bordering the present stream bottom. The vegetation is primarily clover and timothy. A hot stream flows along the base of the bank, but does not serve as a barrier as young marmots crossed it frequently. All of the colony was not studied; that part along the bank and north of the phone line was omitted. Project Number 82.