River otters, once eradicated from Colorado by trapping and polluted waterways, have spent the past 50 years making a comeback.
That recovery began in 1976, when wildlife officials released roughly 125 otters into waterways across the state, including Cheesman Reservoir, the Gunnison and Piedra rivers and Rocky Mountain National Park. The effort also included 27 otters released along the upper and lower Dolores River.
Today, the warm-blooded, semi-aquatic mammals can be seen “periscoping” by standing their torpedo-shaped bodies upright and poking their heads above the water.
Colorado Parks and Wildlife is now commemorating the anniversary while asking residents to help document where otters are living today.
Nate Seward, a local agency biologist, said the goal of the initiative is not to count every otter but to map their distribution and occupancy statewide.
“We know there’s thousands of recreationists out there, hiking or fishing every day. The more eyes out there that we can have to help us document their distribution around the state, the better,” Seward said.
If otters, their tracks or scat are spotted, the agency is asking people to upload a photo or document locations through the iNaturalist website portal or the free app from April through March 31, 2027. Sightings help improve location data, but photos are considered the “gold standard,” providing verifiable data biologists can use to confirm reports, Seward said.
Otters are often confused with minks, muskrats or beavers. The curious, playful animals typically swim with their heads above the water or travel in groups. They are 3 to 4 feet long, have tube-like tails and live in high-quality waterways with diverse fisheries, such as trout, silverfish and especially crayfish in the Dolores.
“Sometimes they’ll actually swim up or lope down the creek bed toward you and let you get a good look or even capture a photograph,” Seward said. “So, we think this is just a great project to solicit citizen science participation.”
The first sighting reported through iNaturalist with photos showed an otter on a snowy bank near Grand Lake. Some biologists believe otters initially released into the Dolores may have traveled as far as 100 miles, with some eventually reaching the San Miguel River.
Public participation is expected to reduce the need for more time-intensive research. CPW will use the data to determine whether river otter populations are widespread and stable enough to consider removing the species from the state threatened list. Any change in status would ultimately be decided by the Parks and Wildlife Commission.
“If we have viable river otter populations and there’s no longer a need for state-threatened status, delisting them would give us more management flexibility,” Seward said.
Agency staff are also developing plans for their own surveys, including rafting trips on the Gunnison, Yampa and Colorado rivers. Seward said the goal is to document otter presence roughly every three miles across about 75 miles of each river to determine whether established populations exist.
awatson@the-journal.com
