A farmer has been caught illegally breeding “massive” mutant sheep to sell to private hunting reserves for up to $10,000, a court in Montana heard.

Arthur “Jack” Schubarth, 80, who owns a 215-acre ranch in Vaughn, Montana, pleaded guilty to criminal charges of wildlife trafficking and conspiracy to traffic wildlife at a court in Great Falls on Tuesday.

Prosecutors say he illegally used tissue and testicles from wild sheep killed by hunters in Central Asia – and the US – to breed hybrid sheep for sale.

According to court documents, Schubarth conspired with at least five other people between 2013 and 2021 to create a larger hybrid species of sheep that would generate high prices from shooting reserves, where people pay to hunt captive trophy game animals.

Schubarth’s ranch specialises in the purchase, sale and breeding of “alternative livestock” such as mountain sheep, mountain goats and various ungulates, according to prosecutors.

They claimed that Schubarth secretly brought parts of the largest sheep in the world, the Marco Polo argali sheep from Kyrgyzstan, into America.

Marco Polo males, which are native to the mountains of the Pamir region of Central Asia, can weigh more than 22 stone with horns that span more than 5ft.

They are protected species internationally and the court also heard how they are prohibited in Montana to protect native sheep from disease and hybridisation.

Prosecutors say Schubarth sent genetic material from the Marco Polo’s body parts to a lab to create cloned embryos. He then implanted the embryos in ewes on his ranch, resulting in a single, pure genetic male Marco Polo that he named “Montana Mountain King” or MMK, the court heard.

Court documents stated that Schubarth worked with the others to use the Montana Mountain King’s semen to artificially impregnate various other species of ewes and create hybrid animals. He agreed to sell one offspring to two people in Texas for $10,000, the court heard.

To move the prohibited sheep in and out of Montana, Schubarth and others forged veterinary inspection certificates, falsely claiming that the sheep were legally permitted species, the court heard. Prosecutors said Schubarth also sold semen from the Montana Mountain King directly to sheep breeders in other states.

“This was an audacious scheme to create massive hybrid sheep species to be sold and hunted as trophies,” said Assistant Attorney General Todd Kim. “In pursuit of this scheme, Schubarth violated international law and the Lacey Act, both of which protect the viability and health of native populations of animals.”

The Lacey Act prohibits trade in wildlife that has been taken, possessed, transported or sold in violation of federal or state law.

Each count carries a maximum penalty of five years in prison and a $250,000 fine. Sentencing for Schubarth is set for July 11.

On a Facebook page in his name which features numerous photos of livestock, Schubarth wrote two days ago: “We have not been able to sell sheep for about three years now. First time in 80 plus years I’m broke.”