BOULEVARD, San Diego County Mustangs shake their heads in the heat, eyes and ears alert to their riders, all of them U.S. Border Patrol agents.
The horses and the agents have gathered for an advanced class at their new facility in this tiny community about 60 miles east of San Diego, near the Mexican border.
Boulevard will soon be home to about half of the San Diego sector's horse unit, with the other half remaining at its Imperial Beach station. The sector plans to boost the unit from 18 to 21, with three more agents by November.
"You can go into an area at night on horseback and practically go undetected, which is a big advantage in what we do," said Jaime Cluff, a supervisory Border Patrol agent.
Bolstering border security, including horse patrols, is a key part of the comprehensive immigration reform bill debate in Congress. The San Diego sector's planned expansion of its horse unit is not part of that bill, but future expansion hinges on its fate in Congress.
In June, the Senate passed a bill calling for $46 billion more over 10 years for border security. The money would support hiring more agents and horse patrols, using 24-hour surveillance systems and building 700 miles of fencing along the U.S.-Mexico border.
The Border Patrol's annual budget for fiscal 2012 was $3.5 billion.
The plan calls for a path to citizenship for millions of people who entered the country illegally. The measure has stalled in the House.
Gauging the security of the country's borders can be difficult. The U.S. Government Accountability Office was critical in a December report of the Border Patrol's ability to measure its arrests. The report's recommendations included setting up goals to improve consistency among the Border Patrol's sectors in collecting data.
Horse patrols are specialized work. Of the 2,600 or so agents in the border patrol's San Diego sector, only 18 work in the horse unit. That's a big change since the Border Patrol began in 1924. Horses were then its primary mode of transport.
The region is isolated and mountainous. Agents say horses have several advantages over vehicles, including lasting longer, better visibility and greater accessibility on difficult terrain. Ranchers in the area often prefer horses on their land to trucks or ATVs.
Cesar Gomez was among the agents receiving instructor training in Boulevard. He grew up riding horses in Woodland and joined the horse unit two years ago in the El Centro sector east of Boulevard.
"It's more hands-on," Gomez said. "It's closer to nature."
Just 10 of the 75 agents who recently applied to join the horse unit were accepted for training, Cluff said, and eight graduated.
Agents learn not only to ride, but feed, saddle and care for their horses, who are considered partners.
"He's going to carry you for six to eight hours out in the field, so you've got to make sure your partner is working," Cluff said.
"You take care of him. He takes care of you," Cluff said. "He pretty much mirrors what the agent feels."
Many Republicans support tighter security measures before addressing Democrats' plans for creating a path to citizenship. Others question allocating more money for security when fewer people are being apprehended at the border.
Border Patrol figures show that apprehensions in the San Diego sector have dipped considerably since 2008, when there were 162,390 arrests. In 2012, there were 28,461. Officials said they do not have separate numbers for the arrests made by the horse patrol.
"The border has never been more secure than it is now. The level of enforcement is unprecedented," said David Shirk, associate professor of political science and international relations at the University of San Diego. "It begs the question of how much more can be gained by increasing enforcement? What will we get?"
Shirk, who conducts research on U.S.-Mexico relations, law enforcement and security along the border, would like to see lawmakers address the issue of the overflow of immigrants entering the country illegally by making legal pathways easier for people who want to work. He suggested raising quotas for visas based on job demand in the United States.
"Then you don't have to worry about people climbing over the walls," Shirk said. "If you gave everyone a chance to come here legally, they would do it."
But others, like Peter Nunez, a former U.S. attorney in San Diego, say that border security should remain a priority. Nunez attributes the drop in arrests to the recession and its effect on the job market.
"There are still hundreds of thousands of people coming to this country illegally every year," Nunez said, calling drug smugglers and terrorists part of the problem. "So, the border's not secure, and there's plenty of work to do."
Nunez is a member of the San Diegans for Secure Borders Coalition, a group lobbying Congress for secure borders, greater enforcement, an employer requirement to use the E-verify system, a cut in legal immigration and the end to so-called birthright citizenship. Though he supports stepping up border security, Nunez would like to see much of the money shifted toward enforcement in the country's interior, including its workplaces.
"The fact that we've had some success doesn't mean we can declare victory," Nunez said.
Meanwhile, Border Patrol agents vie for a chance to "find their seat," which was how Cluff described matching agents with horses.
"Not everybody is cut out for a horse," he said.
Journalist Marisa Agha is based in Southern California.