In 2017, a 14-year-old Idaho resident named Canyon Mansfield took his labrador retriever, Kasey, on a walk on public lands, unaware that a federal agency had set a device known as a cyanide bomb out to control predators.

His experience with that device, known as an M-44, is now one of the stories driving efforts to ban the use of M-44s on public lands.

Two efforts are underway to do so—federal legislation reintroduced earlier this month in Congress and a petition conservation groups filed Thursday with the U.S. Department of the Interior. The petition effort is led by the Center for Biological Diversity and Predator Defense, but dozens of other groups have signed on. 

The petition effort seeks to end the use of M-44s on lands managed by the Bureau of Land Management.

In an East Idaho News video from 2017, Mansfield said that he saw a little pipe that looked like a sprinkler sticking out of the ground “and so I go over and I inspect it and I touch it and then it, like, pops. Makes a pop sound.”

The device spewed a toxic orange substance containing sodium cyanide into the air, poisoning both Mansfield and his dog. Mansfield shielded himself from the sodium cyanide with his arm, but he got the dust on him including in his eye. He washed it off him with snow and cleaned off his eyes.

Mansfield then heard his dog whimpering and saw Kasey in some bushes convulsing.

“I ran over and he had these glassy eyes,” Mansfield said in the 2017 video. “Like he couldn’t see me. He had this red stuff coming out of his mouth.” 

Mansfield went for help, but Kasey ultimately died.

Now his family is pushing to end the use of M-44s on public lands. 

“No one should have to experience what my family and I went through with the death of our dog and the near death of our son,” Dr. Mark Mansfield, Canyon Mansfield’s father, said in a press release announcing the bill’s reintroduction. “Cyanide has no place being used anywhere in the U.S. as a pesticide or ‘lethal control’ weapon, such as an M-44 ‘cyanide bomb.’”

Mark Mansfield called the federal legislation, known as Canyon’s Law, “a simple, common-sense law.”

“Cyanide bombs are a cruel and indiscriminate device that have proven to be deadly for pets, humans, and wildlife – regardless of the intended target,” bill sponsor U.S. Rep. Jared Huffman, D-California, said in a press release announcing the bill. “Families should be able to enjoy the outdoors without the fear of accidentally detonating these devices. They have no business being on our public lands, especially when there are far safer, proven methods to protect livestock, and our bill will bring an end to their use.”

On the Senate side, Senator Jeff Merkley, D-Oregon, is sponsoring the legislation and U.S. Sen. Martin Heinrich, D-New Mexico, is among the senators who has signed on as a co-sponsor.

New Mexico is one of 10 states where a federal agency reported using cyanide bombs, or M-44s, to kill animals last year, a practice that conservation groups say puts people and other, non-target animals such as pets in danger.

While they are often referred to as cyanide bombs, that is a bit of a misnomer as no explosives are used. However, the M-44s can shoot a cloud of cyanide powder up to five feet in the air. 

The M-44s are baited to encourage animals to pull on a material that causes a spring to eject sodium cyanide directly into their face.

Sodium cyanide powder, combined with moisture such as saliva, creates hydrogen cyanide gas. This enters the lungs and poisons the animal.

“I find it incomprehensible that our government is still using cyanide bombs after so many horrific tragedies,” Brooks Fahy, executive director of Predator Defense, said in a press release. “The Department of the Interior has an opportunity to stop this insanity now. I hold out hope they will do so.”

Canyon Mansfield is not the only person who has been injured by M-44s on public lands. 

From 1984 to 2015, 42 people were exposed to sodium cyanide, including 25 Wildlife Services employees and 17 members of the public, according to an analysis by Wildlife Services. Wildlife Services is the agency responsible for predator control on public lands. 

None of those people died immediately after the exposure, but most required medical treatment. 

Pets are more likely to be killed and, in the same month that Canyon Mansfield encountered the cyanide bomb while walking his dog, a family hiking lost their two dogs to M-44s. The family members were also exposed to sodium cyanide as they tried to save the dogs’ lives by washing them in a creek.

In the petition, the conservation groups state that “posted signs warning the public about the placement of the devices cannot alleviate the risks because pets, wild animals, and young children do not understand such warning signs.”

According to the petition documents, the requirement to post signs warning of the M-44s is not consistently followed.

In the Wyoming incident, a family member went back looking for any sign that could have warned them about the M-44s and was unable to find any.

In 2022, six dogs died due to M-44s, according to the petition.

“Going back 25 years, data from Wildlife Services shows that as many as 63 domestic dogs have been killed unintentionally – in a single year – with M44s,” the petition states. “If intentional and unintentional deaths of dogs are combined, as many as 267 dogs were killed by the devices in a single year. Many of these deaths were family dogs running off-leash, and Predator Defense has compiled numerous heart-wrenching stories of families grieving their beloved companions.”

Often these cyanide bombs are used to target predators such as coyotes, but the conservation groups say there are better ways to reduce the conflicts between predators and livestock. The petition highlights methods like livestock guard dogs, range riders and changes in animal husbandry practices. 

The use of M-44s also puts animals at risk that aren’t being targeted.

According to the petition, the U.S. Environmental Protection Agency estimates as many as half of the deaths caused by M-44s are non-target animals such as raccoons, foxes and opossums.

“M-44s are indiscriminate killing devices that are not needed in modern wildlife management because ample viable alternatives currently exist,” the petition states.