We have discovered that dogs can sense body heat radiation with their naked and cold nose-tips (rhinaria). Sensitivity is so high that a sizeable prey animal can be detected from tens of meters distance.
The evidence comes from behavior and brain activity. In Lund, dogs chose correctly between a neutral surface at ambient temperature and a stimulus only 10-12 °C warmer. The distance was 1.6 m and the current record is a stimulus size of only 50 mm in diameter.
Other senses such as olfaction, hearing, and vision could not be used to solve the task. In Budapest, brain activity in dogs was determined by functional magnetic resonance imaging (fMRI). The somatosensory cortex became active upon stimulation with equivalent thermal radiation.
Comparative work has shown that all land-living carnivorans (species in the mammalian order of Carnivora) have cold rhinaria and therefore they may have similar abilities.
The research group Mammalian Rhinarium Group study how mammals obtain sensory information from their rhinaria and what role this information plays in their lives. In the strict sense of the word, the rhinarium is the hairless, often wet frontal part of the mammalian nose.