The Bureau of Land Management’s plan to round up nearly 800 wild mustangs on Wednesday continues to draw pressure from animal lovers, including Gov. Jared Polis and his partner, Marlon Reis.

In the past 24 hours, Polis and Reis sent a two-page letter to Secretary of the Interior Deb Haaland and Nada Wolff Culver, deputy director of policy and programs at the BLM, asking them to freeze the planned roundup at Sand Wash Basin in Moffat County. 

The BLM intends to round up as many as 783 horses out of the herd of 828, although they would return 25 mares and 25 stallions later on. The basin can support up to 362 horses, according to BLM estimates, although BLM wants to cap the herd at 163. 

The Polis/Reis letter calls for a six-month moratorium on roundups.

“There remains legitimate concerns about the fate of gathered horses, and I believe better collaboration with the state and advocates could improve assurances about their long-term well-being and the avoidance of any potential slaughter. There have been concerns raised about how truly accurate the estimates are with respect to ecosystem herd carrying capacity,” the litter said. Finally, the tactics being used for the round up – helicopters – almost certainly creates the opportunity for unintended injuries and particular for the separate of foals from mares.” One observer said 10 foals have been born in the past month in the herd, and based on BLM information, the roundup would not return those foals to their mares.

The BLM cites drought, scorched habitat from wildfires and overpopulation as justification for the roundup, which is scheduled to be done by helicopter. However, advocates for the herd claim recent monsoons have restored the watering holes, and that the land can support far more than 163 horses. They also claim BLM is clearing out the herd to make more room for sheep and cattle grazing, and that using helicopters is inhumane and could result in injuries and even deaths in the herd.

The Sierra Club on Monday added its voice,  claiming that damage to the habitat from livestock is far worse than from horses. 

“As documented by BLM’s own data, livestock grazing, not wild horses, has resulted in damage to the range that is both widespread and severe. Livestock, not wild horses, have resulted in BLM’s own Land Health Standards not being met across much of the Sand Wash Basin Herd Management Area – an area legally designated for Wild Horses by the Wild and Free-roaming Horse and Burro Act of 1971,” wrote Delia G. Malone, wildlife chair for the Colorado chapter of the Sierra Club.

On his Facebook page, Reis has advocated for people to contact members of Congress, including those who serve on the U.S. House Subcommittee on National Parks, Forests and Public Lands, which has oversight of the BLM, and which is chaired by U.s. Rep. Joe Neguse, D-Lafayette, who Reis said “has already expressed a desire to see the BLM conduct herd management differently.”

Last week, Reis said he and Polis met with BLM officials “to discuss ways in which Colorado could become a co-manager of our State’s Wild Horse and Burro herds. There’s a precedent for it currently working through the system in Wyoming. To be clear, the Governor and I both made it known that we do not want Colorado’s Wild Horses to be rounded up, and we want to be a partner in finding and executing more humane management. Unfortunately, as the BLM has Federal level oversight of these animals, the ultimate decision defaults to Washington. We have spoken with Secretary Haaland about stopping the round-ups (and re-listing the Gray Wolf for ESA protections!) twice, in-person. We’ve also written numerous letters to the Department of the Interior and the BLM. We will keep the pressure on, but it’s important for constituents to call and write their Members of Congress (both in the U.S. House of Representatives and in the U.S. Senate).”

The BLM conducted a helicopter roundup of 457 wild mustangs on August 13, according to the Vail Daily, from the West Douglas herd near Rangely, the largest such roundup in history. Ten horses had to be euthanized during the roundup; BLM documents estimate the roundup near Maybell could also result in the deaths of at least eight horses.