In Southwest Colorado, a growing army of everyday scientists scours the mountains for Rocky Mountain bighorn sheep every year.

Mountain Studies Institute started its Colorado bighorn sheep monitoring project in 2018 as a way to gather more data about the movement of bighorn sheep using sightings from trained volunteers. In its fourth year, the program continues to expand as it aims to use citizen science to supplement the work of public land and wildlife agencies. The goal is to both identify areas of potential overlap between bighorn and domestic sheep while also highlighting the risk posed by interaction between the two.

“In addition to raising awareness on the issue, (the Colorado bighorn sheep monitoring project) is also giving specific information on the location of bighorn sheep to try to inform where there might be commingling between bighorn and domestic sheep,” said Artemis Eyster, community science program assistant for MSI and one of the authors of the project’s 2021 report.

MSI and its partners train volunteer citizen scientists to observe bighorn sheep as they move throughout the year. The key is not only to record sightings, but to identify where bighorn and domestic sheep are in relation to one another and the overlap with domestic sheep grazing allotments and bighorn summer range.

“Significant observations” include bighorn sheep on a domestic sheep allotment, domestic sheep in bighorn summer range or scenarios that could ultimately lead to the transmission of disease, such as a foraying bighorn, a rogue domestic sheep or both animals in the same area.

“What’s particularly important is knowing the grazing allotments in the area and the time of season because domestic sheep move around over a pretty large area,” said Doyle McClure, a volunteer observer.

When volunteers see a bighorn, they log their observations on the app and website iNaturalist.org, where observations can be shared on the Colorado bighorn sheep monitoring project’s page.

Eyster and MSI then compile the data from iNaturalist and produce a yearly report that it shares with the U.S. Forest Service, Bureau of Land Management and Colorado Parks and Wildlife.

“One of the benefits of the program is that it is mostly based on opportunistic sightings, meaning that it’s not ‘We're going to try to find a bighorn today,’” she said. “If someone sees a bighorn, then they can add it to the online database on iNaturalist and it can become part of this citizen science collection of observation. It’s a very low barrier form of data collection.”

The project has totaled nearly 1,650 observations and boasts more than 1,050 observers. Of those 1,650 observations, more than 1,500 are “research grade,” according to iNaturalist.

Since the project first started in 2018, annual observations have increased as a growing number of citizen scientists participate. In Southwest Colorado, volunteers totaled 15 observations in 2018. In 2021, they contributed 80.

While the project focuses on Southwest Colorado, it collects data from across the state and has seen observations more than double since the project began.

“We’re continually trying to get more folks involved,” Eyster said. “We do outreach and then there’s other volunteer organizations focused on conservation and wild places and they also try to get their members involved.

“The more people we have that are aware of the program and aware of the risk between bighorn and domestic sheep the better,” she said.

Public agencies and conservation groups have long expressed concern about the potential interaction between bighorns and domestic sheep.

Domestic sheep can transmit bacteria to bighorns that cause pneumonia and can lead to widespread deaths within a wild herd.

According to the U.S. Geological Society, the lead federal agency for wildlife disease research, 50% to 80% of animals die within a herd if exposed by domestic sheep carrying disease.

In its Colorado bighorn sheep management plan released in 2009, CPW noted that interactions between domestic sheep and bighorn were a significant concern for wildlife managers.

“The susceptibility of bighorn sheep to pathogens originally introduced by domestic livestock is regarded as the primary factor limiting Rocky Mountain bighorn sheep populations in Colorado,” the authors of the plan wrote.

Likewise, the U.S. Forest Service has delayed its decision on domestic livestock grazing in the Weminuche Wilderness because of limited bighorn sheep data, according to the Colorado bighorn sheep monitoring project’s 2021 report.

While 80 observations is a relatively small sample size and the opportunistic nature of sightings mean the data from the monitoring project must be taken with a grain of salt, the data collected is critical and supplements the work done by public land and wildlife agencies.

“Whatever we can provide and add to the collective data is invaluable,” said Robyn Cascade, a volunteer observer and volunteer leader for the Northern San Juan chapter of Great Old Broads for Wilderness, an environmental advocacy group.

The data collected by observers adds to the information that wildlife and public land managers can then use to make key decisions about grazing allotments and other conservation initiatives.

For agencies with limited resources, trained volunteers can serve as an additional set of eyes to better understand where bighorn sheep move and how they overlap with domestic livestock. This is especially true since bighorn sheep often live in remote backcountry areas.

“None of the agencies, whether it’s federal agencies that manage land or CPW that manages the wildlife, have the capacity to be on the landscape as much as us volunteers,” Cascade said. “Most of our members are retired (and) we have some flexibility to get out there.”

Observers can also act as an alert system for wildlife managers if they spot domestic and bighorn sheep interacting.

“Citizen scientists are increasingly out on the landscape. We’re really using our wild public land and we may be able to help the agencies respond in a timely manner to help possibly prevent a disease transmission from occurring or from spreading to bighorns,” said Dan Parkinson, a field representative for the conservation group Backcountry Hunters and Anglers and one of the citizen scientists with the project.

Parkinson gave the example of a domestic sheep that strayed into bighorn sheep habitat on North Twilight Peak near Purgatory Resort. A hunter took a picture of the sheep that popped up on the monitoring project’s database and Terry Meyers, executive director of the Rocky Mountain Bighorn Society, was able to contact CPW and the Forest Service to initiate a plan to remove the sheep and prevent possible contact.

“Agencies know that the threat is very real,” Parkinson said.

In its 2021 report, Eyster and the Colorado bighorn sheep monitoring project concluded that bighorn and domestic sheep can overlap in their ranges.

“Data show that bighorn sheep sometimes occupy domestic sheep grazing allotments and adjacent land,” Eyster and Jeremy May, MSI’s education coordinator, wrote in the report.

The report documented 20 significant observations in Southwest Colorado over the last decade, the majority of which have come in the last two years.

More than half identified bighorn sheep on or within 0.1 miles of an active domestic sheep allotment, while another three observations documented domestic sheep on bighorn summer range.

The other five logged stray domestic sheep, close proximity between the two species or bighorn sheep in unexpected locations

“(The project) is clarifying that, yes, there are interactions between the bighorn sheep and domestic sheep and (it’s) being specific about where those are happening,” Eyster said.

Volunteers hope that these observations will ultimately help CPW and the Forest Service to make more informed decisions.

“We hope our data will be used to make scientifically based land and wildlife management decisions, and the more we can accumulate data the more helpful that’s going to be,” Cascade said.

In addition to supplementing public agency data, Eyster said another goal of the monitoring project is to raise awareness about the risk that interactions between bighorn and domestic sheep pose and the importance of public participation in the management of bighorn.

“If the public are also informed, engaged and contributing information, it can help provide support for making hard decisions that involve bighorn sheep populations,” Eyster said.

The project also aims to highlight the value of citizen science for wildlife management.

“Citizen science is an important tool that we should be using and including as we’re making decisions about bighorn sheep,” Eyster said.

For volunteer observers, participating in the project can be captivating. Many volunteers immerse themselves in the study of bighorns as the science spurs their interest.

The allure of bighorn sheep and the difference people can make are two reasons why many people have been joining the project in the last few years, Parkinson said.

“Once people get the bighorn bug, it kind of grabs you,” he said. “Bighorns are the wildest of the wild. They’re this highly rugged, highly evolved species that is very iconic, yet they’re so, so at risk.”

For Cascade, the Colorado bighorn sheep monitoring and citizen science adds another dimension to her enjoyment of the outdoors.

“I think of it as hiking with a purpose,” she said.

ahannon@durangoherald.com