Jan. 4: This story has been updated with details from the Bureau of Land Management on its plan to restrict sales of protected wild horses.

This story was co-published with the Colorado Springs Gazette.

Secretary of Interior Ken Salazar says he will tighten regulations of the federal government's wild horse program, restricting the number of horses people can buy and making it easier for the government to prosecute buyers who sell mustangs to slaughter.

Salazar laid out the plan in an interview Thursday with The Gazette in his Washington, D.C., office, saying the changes were in response to a ProPublica investigation published in September that questioned the fate of animals sold to Tom Davis, a San Luis Valley livestock hauler who has bought more than 1,700 horses through the program since 2009, 70 percent of those sold in that time.

Davis maintains he has found the animals "good homes." Wild horse advocates fear they ended up in Mexican slaughterhouses. Davis subsequently told Colorado officials that he shipped some horses out of state in violation of brand inspection laws. The Colorado Department of Agriculture has turned the case over to the district attorney in Alamosa for prosecution.

Those who buy horses from the federal government already sign contracts saying they will not resell animals for slaughter. Salazar is beefing up the language in contracts to specify that buyers can face prosecution for any "material misrepresentation" on sales applications or bills of sale, or for indirectly selling horses to slaughter by reselling to middlemen.

Under the new rules, buyers also will only be able to acquire five wild horses every six months. Any order larger than that will require the signed approval of the BLM's deputy director.

Salazar said the changes should help prevent horses from ending up at slaughterhouses. He acknowledged, however, that fundamental fixes to the wild horse program, which has been dogged by controversy and mounting costs, have so far eluded his agency.

"It is a problem that has escaped resolution for a very long time for everyone who has tried to work on it," Salazar said. "I don't believe we have the solution yet at hand, but we need to continue to try to figure out the right thing to do."

As Secretary of Interior, Salazar oversees the Bureau of Land Management, which cares for most of the 35,000 wild horses roaming public lands in the West. They are protected by law from harassment, capture or slaughter.

The agency has claimed it screened buyers and that no horses in its care went to slaughter, but did nothing to verify what happened to horses after sales to Davis and others were complete. For years, the agency's sale director in Washington sold Davis truckload after truckload, sometimes contacting him to see if he would like more.

"When I became aware of the magnitude of his purchases and the concerns of illegal activity, I asked the BLM to open an investigation of Tom Davis," Salazar said.

The investigation, opened in June, was initially headed by the BLM, but was transferred to the Interior Department's independent Inspector General in October when it became clear that people in the agency could come under scrutiny too, Salazar said.

"If there was impropriety on the part of the BLM or on the part of BLM officials, the investigation will tell us," Salazar said.

Salazar has lived for decades in the same rural ranching corner of Colorado as Davis. In an interview this spring, Davis said he knew Salazar and had hauled cattle for him for years. The government started selling horses to Davis in large numbers shortly after Salazar took over the agency.

For months Salazar's office did not respond to requests for comment about his connection to Davis.

When a Gazette reporter asked about Davis at a public appearance in Colorado Springs in early November, Salazar pushed the reporter's camera aside and said, "You do that again, I'll punch you out." After his words became the subject of media reports across the country, Salazar called The Gazette to apologize and agreed to an interview.

On Thursday, Salazar denied having any relationship with Davis. "I have never done any business with him," Salazar said. "I have never had a conversation with him. I have never seen a letter from him."

Wild horse advocates applauded the changes Salazar plans for the sale program.

"These are positive steps," said Suzanne Roy, director of the American Wild Horse Preservation Campaign. "It could stop a situation where applications are getting rubber stamp while the BLM looks the other way."

But Roy agreed with Salazar that the fixes don't address the broader flaws in the program.

For decades, the wild horse program has tried to keep herds at target population levels on the range by rounding up thousands of wild horses each year and storing them in government storage feedlots and pastures, including a 2,000-animal facility near Cañon City. The policy has resulted in the warehousing of more and more horses, pushing costs ever higher. Several government audits have warned the strategy is unsustainable.

Shortly after Salazar took office in 2009, he wrote a public letter to Democratic Sen. Harry Reid of Nevada saying "bold actions" were required to bring down costs and "put this program on a more sustainable track."

At the time, there were about 30,000 wild horses in government storage and the program budget was about $50 million. Today, there are more than 45,000 horses in storage and the budget is about $76 million.

On Thursday, Salazar acknowledged progress has been hard.

"I don't believe we have the solution yet," he said. But, he added, the growing cost and captive population "are a reminder we need to continue to try to figure out what the right solution is."

In the 2009 letter to Reid, Salazar said he planned to bring horse populations down to government goals with "aggressive use" of birth control drugs. He reiterated the point in the interview this week, saying the agency needed to "push forward with contraceptive efforts."

Starting in 2010 the BLM set goals for numbers of horses to be treated with contraceptive drugs, but critics say the goals were too modest to be effective and the BLM never came close to meeting them.

The Humane Society of the United States, which has partnered with the BLM to test fertility drugs, says its research shows the agency must treat about 5,000 horses per year to control population growth. The BLM set a goal of treating only 2,000 horses per year and has never actually treated more than about 1,000, according to agency figures.

"It is nice to hear the secretary say we need to use fertility drugs, but actions speak louder than words," said Stephanie Boyles Griffin of the Humane Society, who has worked on the issue for years. "We are seriously disappointed with the small number of horses being treated. It is just window dressing and a complete waste of time."

This month the American Wild Horse Preservation Campaign began circulating an online petition calling for Salazar to resign. The petition now has more than 20,000 signatures.

"Under his leadership the program has not changed direction despite his promises," said Roy, the campaign's director. "There has been no progress, and if anything the program has gone backward."

Salazar, who said he is still deciding whether he will continue as Interior Secretary for another term, acknowledged that the implementation of fertility control drugs has been slow and so far has done nothing to staunch the flow of horses into government storage, but he said he plans to stay the course.

"As vexing as the problem is, as difficult as it is, I think we have made progress," he said, adding that the government is developing new drugs that are easier to use and longer-lasting. "Here is the reality. Unless we do something to get the horse and burro population controlled, the problem is going to continue to grow."

Update (Jan. 4): The federal Bureau of Land Management filled in the details today of its plan to restrict sales of protected wild horses.

Under the revised policies, the agency will sell buyers no more than four horses every six months unless they have special approval from top BLM officials. Buyers will be required to tell BLM agents where they will keep or move horses for six months after the date of purchase. Buyers also will have to pay to ship horses from BLM corals (the agency had been transporting animals for buyers).