A marathon runner has revealed how he survived in the Sahara desert for over a week by drinking bat blood and his urine.

The Marathon des Sables - a six-day, 155-mile race through the Sahara desert - is notoriously tough. So much so that former Olympic pentathlete Mauro Prosperi had to sign a form before he took part telling organisers where he wanted to be buried if he died.

Today, the Marathon des Sables has up 1,300 participants, but when Prosperi signed up he was one of only 80 participants surrounded by desert, and found himself running alone a lot of the time.

Prosperi said he was “bewitched” by the landscape when he arrived in Morocco and by day four of the race he was making good progress at fourth place. But his luck changed when he was confronted with a violent 8-hour sand storm.

“The sand whipped my face - it was like a storm of needles,” he told BBC World Service in an interview.

He was suddenly lost and alone. For the next 10 days, he would have to fight to survive in the unforgiving desert using only a knife, a compass, a sleeping bag and a stash of dehydrated food in his backpack.

Prosperi's survival instincts kicked in immediately, and he remembered that well-hydrated urine is the most drinkable. He was forced to urinate in a spare water bottle, which he didn't touch until the fourth day he was lost.

And to cook his rations, Prosperi urinated on the food in order to save his bottled pee to drink.

On the second day, Prosperi’s hopes of being quickly saved were dashed when he launched a flare at a passing police helicopter, but failed to catch the crew’s eye.

After a couple of days, the runner discovered a marabout, a Muslim shrine where Bedouin nomads stop while crossing the desert, and stayed there for three days. As he climbed the roof to fix his Italian flag to the roof, which he thought would be a clear signal to rescuers, he discovered a colony of bats.

“I decided to drink their blood. I grabbed a handful of bats, cut their heads and mushed up their insides with a knife, then sucked them out. I ate at least 20 of them, raw - I only did what they do to their prey,” he explained.

Propseri began to despair when a second attempt at being spotted by a plane failed, and the runner then took the grave decision to take his own life. He hoped his body would be found at the shrine, so he could quickly be declared dead and his wife could have an income.

But when his suicide attempt failed, he saw it as a sign and found regained his sense of purpose.

The runner remembered advice given him before the race, and headed towards the clouds where he’d be most likely to see other people. During this peg of his gruelling journey, he devoured raw snakes and lizards, and tiny plants on dried riverbeds.

Meanwhile, the organisers and his brother and brother-in-law were scouring the desert for him. While they found traces Prosperi had intentionally left behind, including his shoelaces, they were certain he was dead.

But on the eighth day, the runner’s situation drastically improved. He discovered an oasis, where he simply lay for hours drinking the water. The following day he made his first contact with humans for nine days, when he stumbled upon a small group of women in a large Berber tent, who tended to him and called the police or help.

They told him he was in Algeria, and he had wandered 219km (181miles) off course. At a hospital in Tindouf, Mauritanian, Western Saharan and Moroccan borders, doctors’ told Prosperi that he had lost 16kg during his ordeal, and weighed only 45kg. For months, his body would only allow him to eat liquids, and he did not fully recover for a further two years.