Although the U.S. Border Patrol has increased its presence on the Tohono O'odham reservation, Lt. Michael Ford with the reservation's police force is one of only a few dozen native officers who are responsible for patrolling 4,000 square miles of desert to keep the nearly 30,000 Native Americans on the reservation safe.
The Border Patrol uses the latest night vision technology to monitor people illegally entering the U.S. through tracking thermal energy spots -- a technology so advanced he can spot a rabbit moving in the brush from miles away.
The $18.5 billion spent each year on border security has led to a decrease in the flow of border crossers and an increase in drug seizures -- all of which is the result of more manpower, better technology and constant adjustments to every smuggling technique imaginable.
Securing the border does not come cheap. According to the Migration Policy Institute, a think tank, immigration enforcement costs more than all other criminal federal law enforcement agencies combined.
The U.S. Senate today passed its version of the immigration reform bill, but the fate of the bill's provisions, including additional billions of dollars for border security, remains uncertain since the U.S. House of Representatives has signaled they will be considering their own version of an immigration bill.
"In law enforcement, we're constantly playing catch-up," said Guadalupe Ramirez of U.S. Customs and Border Protection, holding a hollowed out compartment that was made to look like a soda crate. "They will use a compartment until we catch onto it. Once we catch onto it, then the percentage of these compartments that get through drops dramatically, so they change compartments."
But much of the border security inside the Tohono O'odham Nation is done the old fashioned way. It's called "cutting for sign," where trained officers search the ground for footprints, tire marks or unnatural damage to vegetation. Smugglers will often wear camouflage clothing and "carpet shoes," which look like cloth-covered booties, so they don't leave shoe treads in the sand, and they will travel at night when temperatures are cooler.
But the people caught and detained might be the lucky ones. As smugglers and their human cargo make their way across the desolate terrain, often what catches up to them is Mother Nature. Lt. Ford said his force finds, on average, six bodies a week in the desert.
"Once you get out there, you're going to run out of water and you're going to run out of options really quick," he said. "Someone is unfortunate to be out there alone they have no hope of coming back."
The dead are brought to Pima County morgue as nameless casualties. Those who go unclaimed will be buried in unmarked graves. More than 100 bodies were recovered in recent weeks and the heat of summer is just getting started.
As for the Tohono O'odham, tribal members who "Nightline" spoke with said their relationship with the U.S. Border Patrol is complicated, at best.
"Are [U.S. Border Patrol agents] welcome in the nation? I would say yes and no," Verlon Jose said. "We're bringing in people who don't understand our culture, our way of life, therefore there is resentment."
While "Nightline" was out with Border Patrol, agents stopped Art Wilson, a reservation native, for driving under the speed limit. They searched his car, but found nothing and let him continue on.
"This is home [and] it's like somebody coming to your house and enforce[ing]," Wilson said. "There's no sense of freedom, feeling invaded on your own homeland."
The Tohono O'odham continue to struggle to deal with the unintended consequences of the U.S. effort to secure the border with Mexico.
"We are on the same team and we are failing at protecting America," Jose said. "When they say that the border is secure along the U.S.-Mexican border that is not true. They are not secure. If you come to Tohono O'odham they are not secure."
ABC News' Lauren Effron contributed to this report