An 81-year-old Montana rancher was sentenced to six months in federal prison on Monday for running a nearly decade-long scheme in which he used parts from protected wildlife to create a giant hybrid species of wild sheep to sell at premium prices, federal prosecutors said.

The man, Arthur Schubarth, of Vaughn, Mont., illegally used tissue from a Marco Polo argali sheep from Central Asia and the testicles of a bighorn sheep native to the Rocky Mountains to make large hybrids of sheep that he could sell at high prices to shooting preserves, particularly in Texas, federal prosecutors said in a news release.

Mr. Schubarth pleaded guilty in U.S. District Court in Montana in March to two felony wildlife crimes: conspiracy to violate the Lacey Act and substantively violating the Lacey Act, which prohibits the trafficking of illegally taken wildlife.

The Associated Press reported that Judge Brian Morris of the U.S. District Court for the District of Montana said that he had weighed Mr. Schubarth’s age and lack of criminal record to fashion a sentence that would discourage others from attempting to “change the genetic makeup of the creatures.”

Mr. Schubarth’s sentence includes three years of supervised release, according to court documents. He was also ordered to pay a $20,000 fine to the Lacey Act Reward Fund, a $4,000 payment to the National Fish and Wildlife Foundation and a $200 special assessment.

Before sentencing, Mr. Schubarth told the judge, “I will have to work the rest of my life to repair everything I’ve done,” The A.P. reported.

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