DENVER (CN) — In a lawsuit against the United States, a prairie rejuvenation group claims the Department of Agriculture has poisoned 123,000 prairie dogs in Colorado and shot another 39,000 without doing a proper environmental assessment.

The Colorado Prairie Initiative sued the U.S. Department of Agriculture and its Animal and Plant Health Inspection Service, or APHIS, on Feb. 3 in Federal Court.

The nonprofit claims that from 2010 to 2014 APHIS poisoned 123,395 prairie dogs in Colorado and shot 39,174 of them without properly analyzing the impact on other species.

The prairie dogs were killed with zinc phosphide and aluminum phosphide pellets – widely used rodenticides.

“Without proper analysis, these operations risk the populations of not only prairie dogs, but also the myriad grassland species that rely on and associate with the prairie dog colonies,” the group says.

Founded in 2014, the Colorado Prairie Initiative “advocates for the conservation and restoration of prairie ecosystems throughout eastern Colorado,” it says in the complaint. “CPI’s mission is to work toward thriving, contiguous, natural prairies across eastern Colorado sufficient to allow the reintroduction and survival of charismatic species such as bison, elk, and wolves. CPI strives to create prairies reminiscent of the pre-Homestead era, when the state was an untamed ocean of grass.”

Its members are particularly interested in the Front Range, where much of the poisoning takes place. It says prairie dogs are a key species in the prairies, providing “food and support for entire ecosystems,” including those of burrowing owls, foxes, coyotes, reptiles, and other birds of prey.

“Many birds such as mountain plovers and burrowing owls rely on prairie dog colonies for breeding, making prairie dogs an important factor in enjoying many birds in Colorado for years to come,” the complaint states.

The group petitioned APHIS in April 2016 to perform an environmental assessment of the prairie dog program. It took APHIS only a month to reject it. APHIS said prairie dog extermination falls under the National Environmental Policy Act’s categorical exclusions, which exclude certain activities from environmental review if they “do not individually or cumulatively have a significant effect on the human environment.”

Two exhibits filed with the complaint detail APHIS’s categorical exclusion records for two of its prairie dog extermination projects: the first required pest control for a Colorado Department of Transportation project in Pueblo; the second addressed Brighton landowners’ concerns about pasture damage.

Prairie dogs, often viewed as cute and picturesque by city-living tourists to the West, are generally viewed as pests by ranchers and farmers. Prairie dog holes have injured many a horse. The critters live in family groups in prairie dog towns, some of which are so big they contain prairie dog wards. Members of a family interact by kissing and grooming one another. They will not do that outside the family.

A leading prairie dog expert, Northern Arizona University professor Constantine Slobodchikoff, believes prairie dogs have a sort of language by which they warn one another not only that predators are approaching, but what sort of predators and how fast they are coming. Slobodchikoff, an animal behaviorist and conservation biologist, formed the Animal Language Institute in 2008 to share research in animal communication.

In its lawsuit, the Prairie Initiative says APHIS’s categorical exclusion documents contained “no cumulative impacts analysis of the prairie dog operations in the state of Colorado” and did “not analyze the potential impacts of removing prairie dogs from certain areas of the state.”

Colorado has a contentious history in dealing with its prairie dogs.

In 2015, the city of Castle Rock erected the Promenade at Castle Rock, a sprawling shopping center that required extermination of all the prairie dogs in the 160-acres on which the mall would be built. Protesters gathered outside the construction site in early February as the ground crews inside it dropped fumigant pellets down the prairie dogs’ burrows and stomped dirt on top, to suffocate the prairie dogs

In the summer of 2016, the city of Monument came under fire when it sanctioned extermination of local prairie dogs out of concerns they would spread the Zika virus.

The USDA does not comment on pending litigation. The Colorado Prairie Initiative did not immediately return a request for comment.

It asks the court to enjoin continuation of the exterminations until APHIS complies with NEPA and the Administrative Procedure Act, and does a proper environmental review.

It is represented by Trevor Pellerite in Fort Collins.