NEW YORK » The SUV pulled up outside an RV park in Alvarado, Texas, where a homeless man was hanging around, waiting for work doing odd jobs.

The men in the SUV were visiting from Ireland. They had a job for the homeless man, and it was an odd one, all right.

We need you to come with us to a taxidermy shop in Austin tomorrow and buy something, they explained, according to what the man later told the authorities.

We need, they said, a rhinoceros head. Like a trophy that you’d hang on a wall. We want to give it as a gift to our grandfather. We’ll pay you for your time, the Irishmen said.

The homeless man agreed, and so the next day, Sept. 23, 2010, began the strange journey of parts of an animal long dead but newly valuable, winding from the back roads of Texas to an opulent teahouse in Queens to somewhere in China and into the hot drink of some rich old man who wants to feel young again.

The men drove 160 miles to a taxidermy auction house in Austin. The Irishmen had been there two days earlier, to buy the mounted head. But under state and federal law, in Texas only a Texas resident may purchase parts of black rhinos, a protected and endangered species, and it is illegal to transport them across state lines.

"These guys are Irish with Irish accents," said Edward Grace, deputy chief of law enforcement with the U.S. Fish and Wildlife Service. "’Are you residents of Texas?’ They said no."

So the Irishmen returned with the homeless man carrying an envelope with $18,000, and he walked out with the head. They watched as someone sawed two horns off the rhino’s head, Grace said.

Several weeks later, the Irishmen packed the horns and two others into their vehicle, along with some forged bills of sale, and drove to New York.

The value of black rhinos’ horns has skyrocketed recently, with a strong market for them in China and Vietnam, where many people believe that powder from the horns increases male potency and cures afflictions from hangovers to cancer.

This is false, Grace said. "All it is," he said, "is fingernails." But rhino horns can sell for over $5,000 a pound in the United States, and a lot more in China.

Much attention has been paid to the slaughter of rhinos in Africa by poachers who want horns. Less is known about the homegrown poaching in the United States, where traffickers seek trophy rhino heads from taxidermists and collectors.

The authorities have identified organized-crime groups from Ireland that have moved into horn trafficking. Two years ago, Europol, the Pan-European police force, warned of Irish criminal groups stealing rhino horns from art galleries, museums and even zoos. One group has been identified as the Rathkeale Rovers, itinerant families named for the small town where they gather for Christmas and huge weddings and celebrations. The police in Ireland and Britain raided several homes linked to the group in September.

The Rathkeale Rovers came to the attention of U.S. authorities with the 2010 arrest of two Irishmen in Denver buying rhino horns from an undercover agent. "We had never seen that before," Grace said.

The men were from Rathkeale, and the investigation uncovered related U.S. rhino cases, Grace said. "There’s an ongoing investigation right now involving the Rathkeale Rovers buying and selling rhino horns here," he said.

Investigators learned of the Austin purchase and went to Texas. They tracked down the homeless man who had signed for the head in 2010, and were able to identify at least one of the Irishmen who left with the horns that day: Michael Slattery Jr., 23, of Rathkeale. His family has ties to rhino trafficking, according to a letter from a detective for the Irish police, the Garda, that was sent to the U.S. attorney for the Eastern District of New York.

The authorities say Slattery’s journey to New York with the horns ended in November 2010, when he and his partners met a Chinese collector at the Rose House, an English teahouse in the Queens Crossing mall in Flushing. There, amid leather sofas, chandeliers and classical music, the Irish group sold the collector four horns for $50,000, according to a criminal complaint. The horns were resold twice in Queens before they were shipped to China, Grace said.

Slattery returned to Europe, but when Fish and Wildlife learned of the sale, it placed him on an airport watch list. He was arrested Sept. 14 at Newark Liberty International Airport boarding a flight to London, according to the complaint. His partners remain at large.

His lawyer, Lawrence Hochheiser, said of his client, "It’s not like he’s out there killing rhinos."

Slattery pleaded guilty Tuesday to one count of conspiracy to commit wildlife trafficking. During the hearing, he burst into tears.

"Pull yourself together," Judge John Gleeson told him.

Slattery explained that two fellow inmates were arguing over who would be his cellmate. "No way I’m staying with the fellow who’s a murderer," he said. "No way, sir."

He could receive up to five years in prison at his January sentencing, although realistic estimates are closer to two.

"Your life is not ending," the judge told him.

"It’s not, no," he replied.