Stories abound of humans brought up by wild animals, but often they are pure fiction. It's rare to find someone who re-entered society after living in the company of animals and is able to talk cogently about his experiences - including, apparently, sharing food with a family of wolves.

The first time Marcos Rodriguez Pantoja sat in front of a bowl of soup, he didn't know what to do. He looked carefully, cupped his hand and plunged it into the bowl. The contact with the boiling liquid made him jump and the plate ended up in little pieces on the floor.

It was 1965 and he was 19, but he hadn't sat down at a table to eat since he was a small child. He had been living for up to 12 years alone in the mountains with only wolves, goats, snakes and other animals for company.

When he was little - about six or seven, he estimates - his father sold him to a farmer, who took him to the Sierra Morena mountains, to help out an ageing goatherd.

Soon the old man died and Marcos was left alone.

Having suffered years of beatings from his stepmother, he preferred the solitude of the mountains to the thought of human company, and made no attempt to leave.

What little the goatherd had taught him before he died was enough for him not to go hungry. He learned to hunt rabbits and partridges with traps made of sticks and leaves.

"The animals guided me as to what to eat. Whatever they ate, I ate," he says. "The wild boars ate tubers buried under the soil. They found them because they smelled them. When they were digging the soil looking for them, I threw a stone at them - they would run away and then I would steal the tubers."

Marcos says he established a special bond with some animals. Many will find it hard to believe this story, about his relationship with a family of wolves:

"One day I went into a cave and started to play with wolf cubs that lived there and I fell asleep. Later, the mother brought food for them and I woke up.

"She saw me and looked fiercely at me. The wolf started to rip the meat apart. A cub got close to me and I tried to steal his food, because I was hungry as well. The mother pawed at me. I backed off.

"After feeding her pups she threw me a piece of meat. I didn't want to touch it because I thought she was going to attack me, but she was pushing the meat with her nose. I took it, ate it, and thought she was going to bite me, but she put her tongue out, and started to lick me. After that, I was one of the family."

Marcos also says he had a snake as a companion.

"She lived with me in a cave that was part of an abandoned mine. I made a nest for her and gave her milk from the goats. She followed me everywhere and protected me," he says.

These relationships kept loneliness at bay, Marcos says. He was only lonely when he could not hear animals - and in such cases he would imitate their call. He can still reproduce the sound of the deer, the fox, the aguililla (booted eagle) and other animals.

"Once they answered, I would be able to sleep because I knew they hadn't abandoned me," he says.

Bit by bit, sounds and growls replaced words. Marcos stopped speaking - until, one day, he was found by the Guardia Civil, and taken by force to the small village of Fuencaliente, at the foot of the mountains.

His father was brought to identify him.

"I felt nothing when I saw him," Marcos says.

"He only asked me one thing: 'Where is your jacket?' As if I would still be wearing the jacket I had when I left!"

Marcos is a great talker, a storyteller who knows exactly when to pause, when to make a noise, or hiss, to increase the dramatic tension of his tale.

But how true is it? Can men and wolves actually be "friends" or snakes "faithful guardians"?

"What happens is that Marcos does not tell us what happened, but what he believes happened," says Gabriel Janer Manila, Spanish writer and anthropologist at the University of the Balearic Islands, who wrote his thesis on Marcos's case, and 30 years later published a novel about his life.

"But that's what we all do - to present our take on the facts," he says.

"When Marcos sees a snake and gives her milk, and then the snake comes back, he says she's his friend. The snake is not his 'friend'. She is following him because he gives her milk. He says, 'She protects me' because that is what he believes has happened."

This way of interpreting the facts, his imagination and intelligence was what enabled him to survive in the solitude of the mountains, says Janer Manila.

It was thanks to Janer Manila that Marcos's story became widely known.

He listened to Marcos and filmed him 10 years after he had returned from the mountains.

"My first impression was one of amazement. He was a nice young man wanting to communicate with people, despite his limitations," Janer Manila recalls.

"But at first, when I heard it, I did not believe him. I thought, 'It cannot be.' But the story was so consistent and so well told, and also, every time I asked him about it he would tell me the story using the same words. So I said to myself, I will have to check all this."

Janer Manila travelled to the places he had named and talked to the people he had mentioned.

Some people corroborated parts of the story.

"I talked to people who had engaged with him when he was found, with people who welcomed him in their homes, with the employee who bathed him for the first time, with a seminarian who took care of him... All these people highlighted his wild character, his ignorance of the social world and his inability to follow the rules of a game. The account matched what Marcos had told me," says Janer Manila.

"And when I saw him telling his story later," he says in reference to the interviews Marcos gave after the 2010 premiere of a film in inspired by his life, "it hadn't changed."

Marcos describes his return to society as the scariest moment in his life.

"I didn't know where to go; I just wanted to escape to the mountains," he says.

Everything was traumatic, from his first visit to the barbershop - when he thought the barber would cut his throat with his razor - to the fights he had with nuns in Madrid, who tried to make him sleep in a bed.

This habit took him a long time to acquire.

"Once he rented a small apartment and he showed it to me," says Janer Manila. "The bedroom had no bed or furniture, there were blankets all over the floor along with lots of wrinkled sheets of magazine and newspapers, as if there had been an animal there. When I saw that, I asked him if he wouldn't be better sleeping in a bed? And he said: 'No.'"

What most disturbed Marcos most of all was the noise and the hustle and bustle of human communities.

"I could not cope with so much noise… the cars… and people going back and forwards like ants. But at least ants all go in the same direction! People went everywhere! I was scared of crossing the road!" he says.

The nuns of Madrid taught him some lessons.

"They taught me to eat properly and they put a piece of wood in my back to help me walk straight because I was all crooked from walking in the mountains," he says. Also, he remembers, they put him in a wheelchair for a while, because he couldn't walk after they cut all the calluses on his feet.

What followed was a journey from one job to another, and a brief stint in the military.

People regularly took advantage of Marcos's naivety, and he ended up living in miserable conditions in Malaga, until a chance encounter with a retired police officer, who invited him to live in Rante, a small village near Orense in Spain's north-western region of Galicia.

Now in his late 60s, Marcos bears few grudges, but he does wonder why, after forcing him to come down from the mountains, the state didn't prepare him properly for life in society.

"When I got out of there, the first thing they should have done is send me to a school, teach me to talk and how to behave in the world," he says. "What was the point of making me first do communion and military service? So I could learn to shoot and kill people?" he asks, with a rare note of anger in his voice.

In Rante, where Marcos has been living for about 15 years, everyone knows him and treats him with respect.

His home is a small house, with slightly cave-like low ceilings, packed with memorabilia - photos of his moments of fame, drawings and a curious collection of cigarette lighters. The tiny patio is full of flowers and plants.

In the corner of the room there is a piano and a guitar. Marcos learned how to play them by ear and he doesn't play badly at all.

He tells me he had a few girlfriends in the past, but nowadays he is single. He has many friends, though, and people who love him and help him.

He no longer works. He gets a half-pension for an injury he sustained while working on a building site - but whenever he can, he lends a hand at Rante's only bar.

"Marcos is a very good person, a bit childish but a very nice guy. He is always here," says Maite, the owner.

Does he ever contemplate returning to the Sierra Morena?

"I thought about it many times. But I'm used to this life now and there are so many things that I didn't have there, like music for instance, or women. Women are one good reason to stay here," he says.

"Now I am accustomed to it, I'll remain where I am."