Mammals
Star-Nosed Mole
Condylura cristata · also called star-nosed mole
The star-nosed mole is a small, near-blind burrower with the most remarkable face in the mammal world — a ring of 22 pink tentacles around its snout that together form the most sensitive touch organ ever measured. It uses that star to explore, decide, and eat faster than any other mammal.
Overview
Star-nosed moles live in the wet, low-lying ground of northeastern North America — marshes, swamps, wet meadows, bogs, and the muddy margins of streams and ponds. Unlike most moles, they are strong swimmers, and their tunnel systems often open directly into water, where they forage on the bottom. They are active day and night, year-round, including under ice, and they are more social than other moles, sometimes sharing burrow systems.
The star
The star is a specialised touch organ. Its 22 appendages are lined with about 25,000 Eimer’s organs — tiny domed touch sensors packed into a patch a centimetre wide — giving it a density of touch receptors far beyond a human fingertip. The mole rakes the star across surfaces up to a dozen times a second, and a small central pair of appendages acts as a high-resolution “fovea,” like the sharp centre of an eye, that the mole flicks onto anything interesting.
The brain devotes a large, map-like area to processing the star’s input, arranged in the same orderly way vision is mapped in sighted animals — so, in effect, the star-nosed mole sees the world by touch.
The fastest eater alive
By combining the star’s speed with some of the fastest touch nerves known, the mole can locate a prey item, judge whether it is worth eating, and swallow it in as little as 120 milliseconds. It can process food items at more than one per second. This lets it make a living on very small prey — mostly worms and larvae — that would not be worth pursuing at a slower pace.
Smelling underwater
Star-nosed moles are one of only a handful of mammals shown to smell underwater. They blow small air bubbles onto an object or scent trail beneath the surface and then re-inhale them; the bubbles carry odour molecules back to the nose. Water shrews do the same thing.
Reproduction
Females raise a single litter of three to seven young each year in a nest above the water table. The pups’ stars are folded back against the snout at birth and unfurl as they develop.
Status
The star-nosed mole is Least Concern and common wherever there is permanently wet ground. It is harmless, ecologically useful, and rarely conflicts with people. Its main threat is the loss and drainage of wetlands, and it is a useful indicator of healthy marsh and swamp habitat.
Star-Nosed Mole: common questions
What is the star on a star-nosed mole's face?
It is a touch organ, not a nose in the usual sense — the nostrils are in the middle. Twenty-two fleshy, finger-like appendages, eleven on each side, form a fleshy pink star about a centimetre across, and their surface is covered with roughly 25,000 microscopic touch sensors called Eimer's organs, more than the human hand has in total. The mole cannot see well, so it explores its dark, muddy world entirely by pressing the star against surfaces, dozens of times a second, building a tactile picture of its surroundings.
How fast can a star-nosed mole eat?
Faster than you can watch. High-speed video shows the mole touching a prey item, deciding it is edible, and swallowing it in as little as 120 milliseconds — about a quarter of the time it takes a person to react to a traffic light. It can handle and reject or eat several items per second. This is the fastest foraging of any mammal, and it is possible because the star sends information to the brain along some of the fastest touch nerves known.
Can the star-nosed mole really smell underwater?
Yes, and it was a surprise finding. Mammals were long thought unable to smell underwater because scent molecules need air to reach the receptors. Researchers filmed star-nosed moles (and water shrews) exhaling air bubbles onto an object or a scent trail underwater and then rapidly re-inhaling them, effectively "sniffing" the water. The bubbles pick up odour molecules, and the animal reads them on the way back in.
Is the star-nosed mole dangerous or a pest?
Not at all. It is tiny, harmless, eats invertebrates that many gardeners consider pests, and its tunnelling aerates wet soil. Because it lives in marshy, low-lying ground rather than lawns and gardens, it causes far fewer complaints than the eastern mole. Its main vulnerability is the draining and filling of wetlands, which removes its habitat, though it remains common where wet ground persists.