A baby elephant is filmed standing in a small aircraft, eye-to-eye with the pilot, Gary Roberts - an American nurse and missionary. The orphaned calf is the only survivor of a massacre by poachers. This is how Roberts did his best to keep the animal alive.

In March 2013 Gary Roberts received a worrying telephone call. There were rumours, he heard, that 100 elephants had been killed near the border between Chad and Cameroon. Could he fly over the area to check whether the reports were true, the caller asked.

In his Cessna aircraft he managed to pick up the herd's tracks and followed them to an area of low scrub - the massacre zone.

"It was a terrible sight," says Roberts. "It was really just piles of bones that were left because the meat had been extracted." In the two days since poachers had taken the tusks, locals had stripped the carcasses.

"There were large pools of blood on the ground that you could still see from so many animals," he says. The carcasses were spread over a couple of miles. The only way to ascertain the number killed was to count the skulls - Roberts confirmed that nearly 100 elephants had died.

Image copyright Arthur Sniegon

"You'd see 20 or 30 animals in a group that had gone down together," says Roberts. For such large numbers to be killed the poachers would have used machine guns.

"It's really gut-wrenching when you see something like that," says Roberts. "Whether it's in a war where humans are taken down or whether it's where animals are taken down, it's still a sinking feeling in your stomach - it's terrible."

He was quite interested in playing with my controls Gary Roberts

He passed all the information on to the authorities in the Zakouma National Park and returned home. But two days later he got a call back to say that one baby elephant appeared to have survived.

Roberts and his family often take in orphaned animals, so he flew out again to find it, landing at the strip closest to the animal's rumoured location. He questioned the local people, hired a pick-up truck and set off for another village.

The baby had been rumoured to be 25kg (55lb), which is tiny. In fact what he found was a nine-month-old elephant weighing about 160kg (350lb). It had been tied to a tree. The rope had embedded itself in his neck and the wounds had become infected.

The calf was scared, angry and mourning the loss of its family. It was seriously ill - dehydrated and hungry. It had been given cow's milk by the locals, with good intentions, but cow's milk is actually toxic for baby elephants, causing severe diarrhoea.

Image copyright AP Image caption Elephants can just give up and die if they are mourning

"It was getting weak, but also very angry because it had just been tied up to the tree and kids would come by and no doubt throw sticks and rocks at it," says Roberts.

"When I initially approached it, it was trying to bite, it was raising its trunk and trying to charge a little bit, but I just stayed with it and mixed up some formula that we had with us to feed it." After about half an hour the elephant had calmed down enough to be loaded into the pick-up truck.

During the two-hour ride back to the plane, Roberts and his helpers gave the elephant a nickname - Max - because his rescue was challenging them to the maximum. "It was taking everything we could muster to keep him in the back of the pick-up over the bouncy roads," says Roberts.

By the time they reached the airstrip it was dark. There was an added complication - a mob had gathered around the airplane. The local military came to keep the mob from pressing in on them and frightening the elephant.

"It was purely a spectator sport, with no respect for requests to stay back or be quiet," says Roberts. "In the course of events some people threw bricks at the military so they had to arrest a few of the people, in order to keep things under control."

The rescuers - including Roberts' wife Wendy - stayed up all night with the elephant calf trying to keep it calm, and in the morning they lured it in close to the aircraft with a bottle of formula and were finally able to lift it in with the help of several men.

Max took up almost the entire inside of the four-seater plane.

"It was a tight fit definitely," Roberts says.

Max was almost more than the plane could carry, along with the pilot and the other passengers. There was a risk that if he moved around too much, or panicked, it would have become uncontrollable.

"With an animal that size you can feel its weight shifting in the aircraft and I had to have some restraining straps so it wouldn't go all the way to the back of the aircraft - otherwise he would go outside of our controllable range," Roberts recalls.

Max still had diarrhoea and was too weak to be sedated. Instead, they tied ropes around his feet so they could disable his movement if necessary.

"He was quite interested in playing with my controls, he would put his trunk forward and feel my hand and touch the controls and of course feel my face," says Roberts. "It was a bit of a distraction but at the same time a unique experience." Roberts filmed it all on his mobile phone.

When they got Max home he just collapsed, he was so exhausted. He needed 24-hour care and Roberts and his wife took it in turns.

Image copyright Gary Roberts

They slept out under the stars with him, and kept people away so he could rest. They knew that elephants can give up and die when they are mourning loved ones, which was an extra source of worry.

A few days later a volunteer from the Jumbo Foundation Elephant Orphanage in Malawi came out to help, and she brought supplies and a great deal of expertise. "Taking care of a baby starved elephant is very similar to taking care of starved human babies," says Roberts. "The protocol and the procedures are very similar."

We had pulled out all the stops - we had done everything possible Gary Roberts

As Roberts and his wife run a centre for malnourished children, they were familiar with the routine.

But despite their skills, and their best efforts, Max only lived another 10 days.

"We had pulled out all the stops, we had done everything possible," says Roberts, with a sigh.

"Along with the traumatic experience he had been through, to see his whole family massacred and everything compounded, unfortunately he did not survive." The main factor in Max's death was probably the cow's milk - the only kindness he had received during his ordeal in the village.

Max's flight ranks as the craziest in Roberts' experience as a missionary pilot - though the time when he delivered a baby in mid-flight comes a close second.

On that occasion, in Guyana, South America, he alternated between the controls and the birth and managed to safely deliver a baby boy. The umbilical cord was wrapped around his neck, but he survived unharmed.

Roberts is a third-generation missionary for the Seventh-Day Adventist church. His father, a pilot, and his mother, a nurse, raised him and his brother in the Democratic Republic of Congo, in a home that was always full of orphaned baby animals - birds, monkeys, antelope and wildcats.

By the age of 14 Roberts was already assisting his mother with cataract operations. He got his pilot's licence at 17 and then trained as a nurse in the US, where he met his wife Wendy.

Both have been working for a mission hospital in Bere, in southern Chad, helping people in remote villages who have no access to medical facilities, and occasionally evacuating them to hospital.

Their home, too, has been populated by orphaned animals - at the last count, three young monkeys and an antelope - cared for partly by their eight-year-old daughter.

Elephants in Chad

Image copyright Getty Images

Chad used to be known for its free-roaming herds of African elephants, but in a frenzy of poaching some 4,000 elephants were killed in 10 years. Chad's elephant population currently stands at around 1,000, of which 458 reside in the Zakouma National Park. The Fianga massacre, which Max survived, was one of the largest in recent times and happened outside the park. Inside the park, 26 animals were shot in one incident in May 2010. Since then things have improved. There have been no poaching incidents for three years, the elephants have started breeding again, and the government of Chad is training hundreds of new rangers.

Idyllic though this life may sound, it has not been easy. In 2009 their son Caleb, then four, died of malaria.

"You see that happen to other people and somehow you think that having the medical training and being based in a hospital, that won't happen," says Roberts.

With malnourished kids you can't just feed them because you'll actually kill them if you do it wrong Gary Roberts

"In many ways it brought us into a closer relationship with the people who we work to serve… when they see that it's happened to us as well, they can relate better to what we're doing," he says.

Despite pressure from family and friends to return to the US after Caleb's death, the Roberts decided to stay. Another family tragedy, however, has brought about a move to West Papua, Indonesia.

In April, Roberts' father Bob, still working as a mission pilot, was killed on take-off. Gary and Wendy have decided to move to Indonesia to take over his mission, while others will take over from them in Chad.

Roberts admits to sometimes feeling down. "When you see young kids dying from illnesses that should be preventable, in some cases it's very challenging and frustrating," he says.

But the job satisfaction, when it comes, is like no other.

Roberts tells the story of a baby boy who came to the nutrition centre run by his wife.

"Kids will often come in at the last minute - the mothers bring them in literally at death's door - and not too long ago we had a little nine-month-old boy come in and he was literally breathing his last."

The boy was suffering multiple organ failure and spent eight days between life and death.

"With malnourished kids you can't just feed them because you'll actually kill them if you do it wrong, so you have to start a very tedious process of increasing their calorie intake slowly, monitoring fluid overload, heart failure and so on," explains Roberts.

The boy pulled through - and six weeks later, returned to the clinic with his mother.

"I literally could not recognise him," says Roberts.

"He was a fat chubby little happy boy. When you see those cases where you know that if you weren't there those kids wouldn't have survived, it is very satisfying."

Gary Roberts spoke to Outlook on the BBC World Service. Listen again on iPlayer or get the Outlook podcast.

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