The star-nosed mole (Condylura cristata) is a strong candidate for the strangest nose in the animal kingdom. It’s star-shaped rostrum is made up of 22 nasal appendages that it uses to snuffle through water and soil in search of food.
A nose with such an important job could arguably be thought to have a metabolic demand above that of less evolutionarily inventive noses, which would likely require consistent blood flow. This got researchers on a new study wondering, how does this wondrous nose respond to fluctuations in temperature?
“As a northerly distributed insectivorous mammal occupying both aquatic and terrestrial habitats, this sensory appendage is regularly exposed to cold water and thermally conductive soil, leading us to ask whether the surface temperature, a proxy for blood flow to the star, conforms to the local ambient temperature to conserve body heat,” they wrote.
“Alternatively, given the high functioning and sensory nature of the star, we posited it was possible that the rays may be kept continually warm when foraging, with augmented peripheral blood flow serving the metabolic needs of this tactile sensory organ.”
To put the question to the test, they gathered a group of wild-caught participants being kept in captivity and tested the star-nosed moles’ surface temperatures both on the nose and the tail. Their findings revealed that the tail thermoregulated in warm temperatures through vasodilation, meaning it kept to a consistent temperature that didn’t match its environment.
However, for the star-nosed snoot it was a different story. According to the study’s readings, the many appendages of the nose conformed to the environmental temperature, meaning its surface temperature fluctuated and wasn’t being maintained by thermoregulation.
The finding is a curious one given that the researchers say the sensitivity of the nose in consistent regardless of temperature. It’s perhaps the case, then, that it’s an adaptation for preventing heat loss while exploring the world star-nose-first.
And the many tricks of the star-nosed mole don’t stop there. These moles can use their noses to push bubbles of air in and out so that they can smell underwater, which has made them highly proficient at hunting in lakes and streams. According to a 2017 publication, the nose contains more than 100,000 nerve fibers within its fleshy tentacles – five times the amount found in the human hand despite being spread out across a distance equivalent to your fingertip.
Star-nosed moles don’t have functional eyes, but what they lack in sight they make up for with the fovea – a sensory organ that closely mimics that of a visual system. Even weirder yet, they will position the fovea (that sits in the middle of the star nose) in the direction that they’re investigating, indicating that it could be helping them to build some kind of picture of their environment.
These moles are also rapid eaters, capable of eating bugs in less than two-tenths of a second and deciding if they want to eat something or not within 8 milliseconds. Really puts the pathetic speeds of humans’ eating competitions to shame.
The 2023 study was published in the Journal Of Experimental Biology.
6