I love Colorado. I spent a week there in 1993 and had my first taste of mammal watching in the USA. It remains one of my favourite states. Boulder is a great town, and the Rocky Mountain National Park has some of the most spectacular scenery I’ve seen, along with a range of quite visible mammals. Be sure to eat biscuits and gravy for breakfast at every opportunity. I returned in 2011 to spend a few days in Denver in March, and again for a few days more in June.
In June 1993 I saw Eastern Cottontails and Raccoons in the suburbs and was told Musk Rats were findable too. In late March 2011 I looked for Colorado Chipmunks around Boulder but it was still a little too early in the season I think and I didn’t see any mammals. I am reliably informed that Colorado Chipmunks have been caught at a small preserve called Betasso (just up Boulder Creek Canyon) and nearby along Millionaire Drive East (N40.0110, W105.371) a couple of miles west of Boulder. I looked here in June 2011, and also around Flagstaff Mountain (head west on baseline road) which used to be a good spot for them. Although I saw Golden-mantled Ground Squirrels, Red Squirrels, Desert Cottontails and an Abert’s Squirrel (near the amphitheatre at the summit) I couldn’t find any chipmunks.
Colorado National Monument
This area is a beautiful 4 to 5 hours’ drive from Denver. I visited in June 2011 to see Hopi Chipmunks and saw several along the Window Rock trail that runs from the visitor’s centre. There were a lot of Chipmunks around here but at least some were Least.
Driving through the park I also saw a Rock Squirrel, Black-tailed Jack Rabbits, while a White-tailed Prarie Dog crossing the road in Grand Junction.
In 2011 Eastern Fox Squirrels (introduced) were common in Denver’s leafier suburbs. Try around 1400 East 10th Avenue for example and nearby Cheesman Park. I also looked for Colorado Chipmunks around Spruce Mountain where I believe they occur but it was a cold March day and probably too early to see them (I didn’t see any mammals). I returned in June but still no chipmunks: the only mammal was a Desert Cottontail. Spruce Mountain is just off Hwy 25, exit 167, about 40 minutes south of Denver.
Denver Zoo is a good spot to see Thirteen-lined Ground Squirrels. This seems likely to be a remnant wild population as the area used to border the prairie. The best areas to see the ground squirrels appear to be around the little flower bed and giraffe statue right at the zoo entrance. This is just before the entry gate so you probably do not need to go into the zoo to see the squirrels. I also saw some in the shrubbery around the cafeteria to your right when you enter the zoo. The lady working at the gate and seen several that day but they were the first she had seen all year so my timing (late March) was good it seems. The species was much easier to see in June in the same spot. Whatever your view on zoos, Denver is interesting at least in terms of some of the species they have there. I enjoyed seeing Red River Hogs, Yellow-backed Duikers, Fossas and several other species I don’t remember seeing in captivity before.
Fort Collins area
John Fox recommended I look for Spotted Ground Squirrels and Swift Foxes in the Pawnee National Grasslands. In June 2011 his advice proved good. The grasslands are about 30 miles east of Fort Collins. I arrived at dusk and focussed my Swift Fox searching around the ghost town of Keota (which is at the junction of CO Rd 103 and Co Road 390). I arrived at dusk and within 30 minutes had seen two Swift Foxes, Black-tailed Jackrabbits and at least one American Badger all on CO Rd 390, about 1.3 miles north west of the junction with CO Rd 103. But things change: see Charles Hood’s 2013 update of a trip to the same area when he couldn’t find a Swift Fox.
Early the next morning I looked for a Spotted Ground Squirrel. I didn’t find one but did see a Thirteen-lined Ground Squirrels very near to where I had seen the animals the night before.
I set some traps along the roadside overnight. In the morning I had caught a Western Harvest Mouse and an Ord’s Kangaroo Rat.
The grooves on the Harvest Mouse’s incissors, which are diagnostic, were really very distinctive.
Great Sand Dunes National Monument
I spent a night here in July 2003 and saw many Ord’s Kangaroo Rats.
In June 1993 Mountain Goats were pretty easy to spot up at the summit where they lick salt from the road. These animals aren’t so easy to see elsewhere in the Rockies south of Canada.
We saw plenty of Pronghorn Antelope along the highway as we were driving up to Dakota and Wyoming from Boulder.
Rocky Mountain National Park
I spent several nights in this beautiful park in June 1993 and enjoyed a lot of wildlife. Species included a Pika (at a roadside view point high on a scree slope), Eastern Cottontails and Yellow Bellied Marmots were common.
Golden Mantled Ground Squirrels, Wyoming Ground Squirrels, Least Chipmunks, Red Squirrels and Big Horn Sheep were also easy to see. I saw my first Beaver at the Cub Lake Trailhead at dusk. While elsewhere in the park I saw my first Coyote, Elk and Mule Deer.
I was back in March 2011 and saw Big Horn Sheep just outside Estes Park, as well as a couple of Red Squirrels and many Elk inside the park.
Colorado, 2023: Joey Bunk with 8 species including Bighorn Sheep and Black-tailed Prairie Dog.
California to Colorado via Washington, 2023: Brian & Eileen Keenan’s report featuring mammals including Thirteen-lined Ground Squirrel and Silver-phase Red Fox in Colorado and Aplodontia in Washington.
Colorado and New England, 2019: Samuel Marlin, a few days & 28 species including New England Cottontail, Moose and Bighorn Sheep.
Fort Collins, 2018: Marcus Zokan, 2 days & mammals including Western Small-footed Myotis and Beaver.
South Central Rockies, 2017: Sjef Ollers, 3 weeks & 44 mammals including American Badger, Swift Fox, Black-footed Ferret and Long-tailed Weasel.
Western USA, 2017: Romain Bocquier, 40 days & 84 species including Hooded Skunk, Fisher and Banner-tailed Kangaroo Rat.
Colorado, 2017: Ben Schweinhart, a short note covering 20 or so observations including Swift Foxes, plus the tracks of a Lynx.
Colorado, 2017: Richard Webb, 1 week & 18 species including American Marten, Moose and Montane Vole.
Western Rodents, 2015: John and Karen Shrader, 10 days & 35 species including Apache Pocket Mouse, Banner-tailed Kangaroo Rat, Plains Harvest Mouse and Spotted Ground Squirrel.
Colorado & a little bit of California, 2014: Michel Watelet, 2 weeks & 34 species including Bobcat, Abert’s Squirrel and Bighorn Sheep.
Colorado, 2013: Hugh Buck, 11 days birding & 21 mammals including Colorado Chipmunk and a Bobcat.
The Southwest, 2012: Vladimir Dinets, 1 month through NW New Mexico, N Arizona, SE Utah and Colorado with selected highlights (mainly interesting rodents and bats).
Colorado, 2008: Mark Hows, 2 weeks & 34 mammals including a Cougar and a Badger.
Chipmunk ID Mesa Antero, Chaffee County, December 2023.
Denver area RFI, June, 2019
Pawnee Grasslands, August, 2013 – some information on visiting the grasslands to see Swift Foxes and other species.
Black-footed Ferrets in Colorado, November, 2013
RFI – for Chipmunks and Ground Squirrels in California, Colorado and eastern Utah, June, 2011. Covering Hopi Chipmunks, Spotted Ground Squirrels and more.
Colorado Chipmunks RFI, March, 2011. A discussion about where to see Colorado Chipmunks, Spotted & Thirteen lined Ground Squirrels and other rodents and shrews).