Researchers believe they have solved the mystery surrounding dogs' noses and why they are so cold.

A study revealed the phenomenon is down to their sniffers serving as ultra-sensitive heat detectors - and not anything to do with body temperature regulation.

Scientists in Sweden and Hungary found that when the ambient temperature was 30C, a dog's rhinarium - or the bare end point of the nose - was 5C cooler.

And when the outside temperature was 0C, a dog's nose would be about 8C. The two factors equal out at 15C.

Such differences suggest the tip of the nose serves as a sensory function, according to the study published in the Scientific Reports journal.


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It showed a dog's nose can detect very faint heat sources - such as small animals - from 1.5m (5ft) away.

Researchers from Lund University and Eotvos Larand University studied three dogs, who were trained to identify which of two identical four-inch wide objects had been heated 12C warmer than room temperature.

"All three dogs could detect stimuli of weak thermal radiation in double-blind experiments," said the researchers.

"In addition, we employed functional magnetic resonance imaging on 13 awake dogs, comparing the responses to heat stimuli of about the same temperatures as in the behavioural experiment. The warm stimulus elicited increased neural response.

"All stimuli of radiating heat used in our experiments were too weak to be felt by human hands, even at very short distances. We had to touch the surfaces to feel the warmth."