The star-nosed mole is a semi-aquatic animal that prefers swamps and wet fields as its habitat. (Photos by Mary Holland)

Streamlined body, strong, wide front feet, lack of external ears, short appendages, velvety fur that can lie flat in two directions—everything about a mole is built for its subterranean existence. All seven North American species of moles share these characteristics, but there is one species—the star-nosed mole—that has an additional, unique adaptive feature for which it is named.

Moles possess numerous tactile hairs on their noses, as well as highly sensitive tactile organs called Eimer’s organs, which are very sensitive to touch. Due to poor eyesight, (not an important sense when one’s life is spent mostly in pitch-black tunnels), moles are dependent upon these structures to navigate and locate prey. Whereas most moles have a few thousand Eimer’s organs surrounding their nostrils, star-nosed moles have as many as 25,000 to 30,000. In addition, they have 22 fleshy, pink rays of varying lengths. All of these rays contain nerves and blood vessels and are very sensitive to touch. They are constantly in motion when the mole is active and appear to be exploring the mole’s environment.

The star-nosed mole can use its nose as a snorkel when swimming underwater.

The actions of these rays are quite complex. In general, the more excited the mole, the faster the rays move. The rays can all point forward, or can be fanned out. Star-nosed moles have been observed moving their head and nose side to side and sweeping their star’s rays forward and backward while they feed in shallow water or soil. The center-most short rays repeatedly touch prey before and as it is being eaten. One study suggests that these rays may allow the mole to sense electrical stimuli, such as that given off by earthworms, a favorite food of star-nosed moles, but this has not been confirmed conclusively. What is known is that while the rays seem to assist in locating prey, they are not used to capture prey, manipulate objects, or position food that is being eaten. In addition to being an aid in securing food, the entire nose, including all of the rays, of the star-nosed mole can be elevated in order to form a snorkel that they use when swimming under water.

The star-nosed mole is rarely responsible for the tunnels and mole hills found in lawns, for the soil there is usually too dry. The star-nosed mole is semiaquatic, as much at home in the water as it is on land. Thus, it is found in wetter environments than other species of moles. Look for these moles in swamps, wet fields, and other wetlands that could be described as “mucky.” It is a skillful swimmer, using its broad front feet as oars and its tail as a scull. An average dive lasts about nine seconds, but these moles have been known to remain submerged for up to 47 seconds. Star-nosed moles have even been observed swimming under the ice in winter.

Earthworms are a primary source of food for star-nosed moles, but they also consume a variety of aquatic prey, including leeches, caddisfly and midge larvae, crustaceans, and even small fish. Much of the food they eat is gathered by rooting in the mud of a stream bottom.

Like other species of moles, star-nosed moles dig two types of tunnels—deep, permanent tunnels and more shallow tunnels. The soil that is removed during the construction of the deeper tunnels appears as small, conical piles of earth, much like those that a crayfish produces, but the star-nosed mole’s piles lack the obvious opening that the crayfish’s has. It is not unusual for the tunnels to lead directly into a stream or pool.

The chances of coming across a star-nosed mole are not great, for they tend to forage above ground only at night, though they occasionally emerge during the day. If you should be lucky enough to spot one, watch the constant motion of the ring of rays. Thanks to these appendages and their sensitivity, star-nosed moles can zero in on prey quickly and accurately.

 
Naturalist and writer Mary Holland lived in Harvard for many years before moving to Vermont. She can be contacted at mholland@vermontel.net.