Last year, 322 deaths were recorded along the US border with Mexico. The real number could be a lot higher. Alex Hannaford joins volunteers searching for the lost

It’s relatively easy to spot bones in the desert. Bleached by the sun and set against the brown, sandy soil that’s peppered with sagebrush and mesquite, they almost glow white. Once you start looking it seems they’re everywhere. Mostly it’ll be a rabbit’s skull or the hip bone of a small mammal. Sometimes, though, they’ll belong to a human.

On 22 April, there were ribs, a shoulder blade, a clavicle, a piece of vertebrae and a jawbone. There was also a pair of dark-coloured trousers, size 9 Adidas trainers and a yellow wallet with a Tasmanian Devil cartoon on the flap. Inside was a photocopy of an ID card which read: Republica De Honduras. Filadelfo Martinez Gomez. Date of birth: 8 August, 1992.

He died under a tree, most likely of dehydration, on the edge of a dried-out rainwater wash – one of many indents in the sand that snake down from the Growler Mountains here in southern Arizona. He was found 37 miles north east of the Mexican border town of Sonoyta, from where he’d come. There were some other bones scattered 600m to the east – and a skull, two miles west.

This is America’s secret graveyard, where families are forbidden from visiting the final resting place of their loved ones, and often don’t know they are there at all.

Last year, there were officially 322 deaths along the US border with Mexico. Human remains were found in the deserts and remote ranchland in Texas, Arizona, New Mexico and California. In the past decade there have been 4,205. It’s an estimation because these are just those they have recovered. There are probably hundreds more hidden under trees in that scorched Arizona desert alone. All were migrants: men, women and children heading north for a better life, often carrying just the clothes they were wearing.

Filadelfo Martinez Gomez was 22 when he left his home in Honduras with just a change of clothes.

In Sonoyta, migrants are told by the “Coyotes”, people-smugglers they pay to help them cross, to “hug the granites” – the mountains that rise from the desert floor in a line northwards. They tell them they’ll need two litres of water for a two-day hike to get to the relative safety of the Arizona town of Gila Bend. From there they can hitch a ride on highway 85 north towards Phoenix and beyond. But the migrant trail from Sonoyta to Gila Bend doesn’t take two days. It takes 10. And you run out of water long before then.

Until there’s a DNA match, the bones found here on 22 April have officially been assigned a case number by the Pima County Sheriff’s Department. They probably belong to Filadelfo, but for now he is simply 170422145. According to the postmortem, the cause of his death is undetermined: flesh can tell stories; skeletal remains offer up few clues.

Facebook Twitter Pinterest A clue: the ID papers of lost migrant Filadelfo Martinez Gomez are found.

The remains were discovered by Aguilas Del Desierto, the Eagles of the Desert, a group of 20 or so mostly Hispanic men (and some women) who live in California and Arizona. Each month Ely-Marisela Ortiz, who founded the organisation in the summer of 2012, drives the 325 miles from his home in San Diego to the remote Arizona town of Ajo, on the edge of a vast desert wilderness known as Cabeza Prieta – Spanish for “dark head”.

For two days Ely’s volunteers search on foot in some of the most inhospitable terrain in the United States in the hope they’ll find migrants alive so that they can give them water and call for help. Often, though, they’ll find their bodies or bones. The only hope they have then is that they can successfully repatriate their remains with their families, giving grieving relatives some kind of closure.

Filadelfo was just 22 in June 2015 when he left his home in San Antonio de Cortez in Honduras. He’d always talked about leaving, but when he finally did he didn’t tell his parents he was going. His sister Olga knew; he asked her to make corn tortillas for his trip. “He just had the clothes on his back and a change of clothes in a backpack,” she told me over the phone, via an interpreter. “He said he’d buy food and water along the way.”

He took a bus to the nearby town of San Pedro Sula, then an overnight bus into Guatemala. From there he walked, hitch-hiked and rode buses, sleeping rough or in immigrant shelters. Every eight days he’d call his family. Eventually he made it to Mexico where he stayed for a year, making several attempts to cross the border, and sending what little money he could back home, including some for his niece, Olga’s daughter. That ended the day he walked into the desert of Cabeza Prieta.

The fourth of eight children, Filadelfo grew up in a poor, hilly, rural town in the north west of Honduras. His parents, Francisco Martinez Diaz and Alba Lydia Gomez Jacinto, worked in the cornfields and rice farms, and when Filadelfo wasn’t at school he’d help them out, working the land.

He loved listening to ranchera music, playing football with the neighbourhood kids and watching his favourite team, CD Marathón, play in the national league. Olga remembers when he was 10 years old he climbed a tree to cut branches with a machete for firewood when he fell and suffered a small cut on his arm. Olga was cleaning the blood off in the bath when their mother came in, saw the red water, and began screaming. “It was no big deal,” she said. “The water made it look worse. But we’d always laugh about that.”

Facebook Twitter Pinterest Not forgotten: a makeshift cross marks the spot where a body has been discovered, among the animal bones in the desert. Photograph: Caitlin O'Hara/Getty Images/The Observer Magazine

When Filadelfo turned 13 he got a job milking cows, but Olga said he didn’t think he was making enough money and desperately wanted to help their parents. “He had heard stories people told about going to the US and planned to travel there with friends from San Antonio.”

On 18 June 2016, he called home to say he was about to walk into the desert. “I told him not to go; that he was doing fine in Mexico,” Olga said. “But he said one of his friends was going and he had decided to help him.” Olga choked back tears. “His last words were, ‘Take care of our parents,’ and he told me if he didn’t call within two months, he was dead.”

It is just before 6am when I pull into the car park of the Circle K convenience store on the edge of Ajo, Arizona. Soon after, five or six trucks and SUVs arrive with large stickers on the sides saying “Aguilas Del Desierto”. Some of the volunteers have driven through the night from California to get here.

Ely-Marisela Ortiz, a quiet, stoic man with thick black hair and moustache, climbs out of a truck and unfurls a map, while volunteers, clutching gas station coffee and energy drinks, gather round. “Today we’ll be hiking for about 10 miles, in the shadow of a mountain,” Ely tells them in Spanish. “It’s going to be hard.”

The area they’re about to search is vast, encompassing federal land, the Barry M Goldwater military range and the Cabeza Prieta wilderness. The Eagles have received reports from two families saying their loved ones are missing – part of a group abandoned by smugglers 10 months earlier, somewhere along the migrant route between Sonoyta and Gila Bend.

“Always maintain a line of sight with the person to your right and left,” Ely says. “If you feel ill, let us know. If we find bones, don’t touch them. It is forensic evidence. If you see cartel members, don’t interact with them. If we find migrants alive, don’t crowd them.”

Facebook Twitter Pinterest The lost ones: the corpse of a migrant who had attempted to make the crossing. Photograph: Caitlin O'Hara/Getty Images/The Observer Magazine

For Ely, sending his team to search this particular route brings back painful memories. In the summer of 2010 the remains of his brother, Rigoberto, and cousin, Carmelo, were found here after they were both left behind in the desert by people smugglers. Rigoberto, an undocumented immigrant, was deported from the US, forced to leave his wife and children behind in Oceanside, California. The summer he lost his life he was trying to return to them.

Ely asked for help finding them from the Mexican consulate, immigration officials and human rights organisations, but he says no help came. Ultimately, it was a group like his who found them. Afterwards, Ely volunteered with that organisation before starting his own in order to put more boots on the ground.

He doesn’t take part in the searches any more, instead planning routes, raising money, and waiting with the trucks in case of an emergency. Last year he suffered from heat exhaustion out in the desert. “I thought about my brother at that moment,” he tells me. “I realised that was the same way he went, and at that point I knew the agony they felt at those last moments; when your body doesn’t respond any more you can’t take one more step.”

We drive along a dirt road for a few miles. Dust flies up from the truck tyres and for most of the journey we can’t see more than 10ft in front of us. We park at the side of the track and most of the volunteers grab walking sticks and put on yellow high-visibility jackets and snake gaiters – thick strips of canvas fastened around the ankles to absorb any bites from rattlers.

We begin walking, 20 volunteers, each 50 yards apart – an army of yellow fanning out across the silent, scorching desert. A lizard darts across the rocks as we pick our way across bullet casings and exploded ordinance on the military range, round ironwood trees and thorny mesquite. When we stop to rest, we have to sit on backpacks as the ground is rife with minuscule thorns that stick in your skin. I look around; this is the last thing Filadelfo would have seen.

A few months ago one of the volunteers found a mobile phone in the desert, near four different piles of human remains. “It was dusty but when we got home we managed to charge it up and it turned on,” José Genis, one of the organisers, tells me. There was no pass code and José discovered that the last number dialled was 911 – the call lasted 11 minutes. Eventually they got the recording of that phone call from police. José starts to well up. “I’m sorry. This is hard for me. The man was on the phone asking for water in Spanish, telling the operator he was dying. They forwarded the call to border patrol who told me they went out to search but couldn’t find him.”

Roberto Resendiz, a volunteer from near San Diego, radios to say he’s found something. When we get there there’s no mistaking what it is: a human skull. Roberto pulls two pieces of wood from his backpack, and a length of ribbon. He fashions a small cross and pushes it into the ground. Another volunteer seals off the area with tape while someone else snaps photographs of the scene. José pulls up the coordinates on a GPS unit and writes them down to send to the medical examiner later.

Facebook Twitter Pinterest Taking a break: volunteer Juan Carlos Genis, 14, rehydrates in the Cabeza Prieta wilderness, after hiking six miles in temperatures over 95F. Photograph: Caitlin O'Hara/Getty Images/The Observer Magazine

Within minutes, someone else radios to say they’ve found more remains, just 60m away. As I approach, the stench is strong. There’s a hip bone, bits of femur, a sock and some scraps of clothing. Under a nearby mesquite tree is a pair of black trainers, two water bottles and several pieces of ribcage. “It looks like an animal dragged him – probably a coyote,” someone says. Next to that is some charred desert grass; it’s likely he set it on fire so he could be found.

José calls me over. He’s found an ID card: Dennis Nunez, born 1986 in Honduras. Tomorrow, another volunteer, Cesar Ortigoza, will post a photograph of Dennis’s ID card on the Eagles’ Facebook page. He did the same with Filadelfo’s ID in April. Within five minutes, 200 people had shared the image. Within 24 hours, it had been seen by 1,500 people, one of whom posted it on the Facebook page for the tiny town of San Antonio de Cortés where Filadelfo lived. Then Filadelfo’s family got in touch.

One of the volunteers, Jason Bechtel, suddenly feels faint and almost passes out from heat exhaustion. He’s made to lie on a stretcher and we carry him to a shaded spot where José straps a portable blood pressure machine to his arm. It illustrates just how quickly and savagely you can succumb to the desert heat.

“Otra muerte,” one of the volunteers shouts. I understand barely any Spanish, but I know what it means: another death. A few metres away, lying under a creosote bush, next to a pair of trainers and two water bottles, is the body of a man. He’s probably been dead a week. His rib cage protrudes from what’s left of the skin on his chest; his black hair is still intact.

Flies hover around the cavity in his chest and the smell is unbearable. José cuts down the branch of tree so he can better access the body. He puts on a pair of rubber gloves, pulls his scarf up over his nose and mouth, and bends down on one knee to begin searching in the man’s pockets for identification, but there is none. “Tell the British people that for some this is the end of the American dream, right here,” one volunteer, Pedro Fajardo, tells me.

Olga said Filadelfo’s family waited every day for his call. When a month passed and they’d heard nothing, she began to get really worried. “After two months I just kept hearing the words he had said and I knew he had died.” They are still awaiting the results of the DNA test by the Pima County Medical Examiner. But they are sure it’s him. “We feel liberated because we know now,” she said. “Having an answer is easier. It means a lot to be able to bury him in his home town of San Antonio.”

Back in the desert the sun sets once more on America’s secret graveyard. Soon, the coyotes will emerge from their dens and more migrants will attempt to hug the granites and reach Gila Bend.