The rust-coloured animal was seen by a tourist at Uhuru peak, the mountain's highest summit between 5,730 and 5,895 metres above sea level where temperatures range from minus four to 15 degrees centigrade.

The sighting has baffled animal scientists who have questioned what motivated the dog to scale such heights and how he could have survived without a proper food source on the desert-like, stony plains of the volcanic Tanzanian mountain.

One veterinary expert suggested that the dog might be rabid – one explanation for his mountaineering inclination – are warned other climbers to keep a safe distance.

Antoine le Galloudec, a French tourist, was climbing the mountain with three colleagues and took a picture of the dog using his mobile phone.

In an email to Tanzania's Citizen newspaper, Mr Galloudec said he spotted the dog when he went to answer the call of nature.

"I saw the dog lying one metre away from where I stood on a rock," he said.

Abel Edward, from Ahsante Tours which hosted the group, told The Citizen that a dog was spotted at Baranco Camp (3,960 metres above sea level) on the mountain 10 years ago.

"When the tourists showed us the picture of this dog we could not believe our eyes," he said. "How it survived in such freezing conditions and what it ate during that time remains a mystery to us."