• Dogs' noses are cold so they can detect the heat radiating from objects nearby, a study has found.
  • They could potentially sense a small mammal from 1.5 metres away.
  • The dogs' noses could feel heat more sensitively that human hands.

A scientific study has answered a question on a lot of people’s lips about a lot of dogs’ noses: Why are they so cold?

While it has been widely assumed the phenomenon is related to body temperature regulation, researchers have now revealed it is because dogs’ noses serve as ultra-sensitive heat detectors.

© A Bálint et al. (2020) (https://creativecommons.org/licenses/by/4.0/)
This thermal image shows how much colder a dog's nose is than the rest of its face © A Bálint et al. (2020) (https://creativecommons.org/licenses/by/4.0/)

In a study published in Scientific Reports, a team of researchers from Sweden and Hungary found when the ambient temperature is 30°C, a dog’s rhinarium – the bare end point of the nose – is some five degrees cooler. If the outside temperature is 0°C, a dog’s nose will be around eight degrees. The two factors equal out at 15°C.

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The researchers believed such differences suggested the tip of the nose served a sensory function, and that hypothesis has been proven correct. The study showed a dog’s nose can detect often very faint heat sources – such as the presence of a small mammal – from 1.5 metres away.

The research team from Sweden’s Lund University and the Eotvos Lorand University in Hungary studied three dogs – Kevin, Delfi and Charlie – who were trained to identify which of two identical four-inch wide objects had been heated to around 12 degrees warmer than room temperature.

“All three dogs could detect stimuli of weak thermal radiation in double-blind experiments,” the study said.

“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.”

Reader Q&A: Why do dogs tilt their head when you speak to them?

Asked by: Toby Graham, Shrewsbury

A dog’s range of hearing is wider than ours but not as accurate. Perking their ears up while tilting their heads helps them pinpoint where noises are coming from more quickly. It also helps them to hear and interpret the tone of our voices, and pick out familiar words such as ‘walkies’.

Dog behaviour expert Dr Stanley Coren believes that dogs with shorter muzzles tilt their heads less because they have a better view of our facial expressions and are therefore not so reliant on their ears to understand us.

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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.