Moles

Moles are very diverse and widespread within the United States. They spend almost all of their time underground and some are even semi-aquatic. Although their presence is well known by their recognizable mounds, they are rarely seen and little is still known about these beneficial critters.

There are seven species of moles (Talpidae) in North America; only three live in Washington. Two species -- the Townsend's Mole and the Coast or Pacific Mole -- are responsible for building the molehills and the third species, the Shrew Mole, does not build extensive burrow systems but spends time on the soil surface or under leaf litter.

Two Townsend's Moles in an aquarium

Townsend's Moles

Description

Moles are highly specialized digging machines. They have a long tubular body, no external ears, and their limbs are close to their body. They have broad, shovel-like forelimbs that allow them to power through soil. They have very small eyes that are only good for light detection. Their pelt is soft and velvet-like.

The Townsend’s Mole (Scapanus tonwsendii) is the largest mole in North America and is eight to nine inches long.

The Pacific Mole (Scapanus orarius) ranges from six to seven inches long and similar in appearance to the Townsend Mole.

The Shrew Mole (Neurotrichus gibbsii) is the smallest mole in North America. It is unique to the Pacific Northwest and is four to five inches long. As the name suggests, this mole is shrew-like in appearance and lacks a typical mole’s developed forelegs for digging.

Did you know? Moles have an extra thumb on each forepaw, making them polydactyl.

Ecology

Habitat
Moles are fossorial and spend the majority of their life underground. The exception to this is the Shrew Mole which spend its time under leaf litter. They occur in a variety of habitats from subalpine meadows to lowland swamps and in a variety of soil types. Some prefer moist soils while other prefer drier, but overall, moles prefer soils that are easy to burrow in. The most important factors affecting their habitat choice are soil type, soil condition and moisture, and food availability.

Burrows, tunnels, and nests
A mole’s territory is made up of a complex system of tunnels. All species construct two basic types of tunnels: Deep, more permanent tunnels and shallower surface runways. Surface runways are located one to four inches below the surface and appear as three-inch-wide ridges in the soil. Surface tunnels connect with deeper runways that are three to 12 inches below the surface but can be as deep as 40 inches. These are main passageways used daily as the mole travels throughout its territory. Located deep within the tunnel system are a nest where females birth and raise young and an area for storing food.

Did you know? Moles have to ability to tolerate higher levels of carbon dioxide and actually reuse oxygen inhaled above ground to help them survive underground.

Development and Family Structure

Moles are typically solitary creatures. Mating season in January and February is an exception, when males will seek out females. Females give birth about four to six weeks after mating. Young moles spend 30 to 36 days with their mothers before dispersing to find their own territories. When they disperse, the young moles usually move above ground at night, where many fall prey to owls, coyotes and other nocturnal predators.

Foraging

Most North American moles are insectivorous, but moles in Washington eat both plant and animal matter. A mole’s diet is mostly insects and other invertebrates including earthworms, centipedes, millipedes, snails, slugs, grubs, ants, termites, beetles and crickets. Townsend's Moles will also eat grass roots, vegetable crop roots and bulbs.

Mole saliva contains a toxin that paralyzes its prey. This allows them to store prey that is still alive in their underground lair to eat later.

Did you know? One mole can eat 50 pounds of worms in one year.

Behavior

Moles are generally solitary and will aggressively defend their burrow systems. They are rarely seen due to their subterranean lifestyle. But you usually know when they're around. As moles excavate and maintain their underground burrow systems, excess soil is pushed to the surface forming molehills. Although those who maintain gardens or lawns often view moles negatively, the burrowing is actually beneficial. It aerates and mixes soil layers and improves drainage.

Did you know? Moles can dig up to 18 feet an hour.

Living with moles

Most conflict situations have to do with the molehills. Moles do sometimes harm plants, although inadvertently, by uprooting or covering them up as they diligently excavate. Moles do occasionally eat plant matter such as roots, tubers and bulbs. The presence of moles, however, is likely to be more helpful than harmful to the health of the soil on your property.

Excluding moles from your entire yard is difficult, but there are ways to prevent them from gaining access to your flower or vegetable gardens.

Gardening
Create raised beds for your garden and ornamental plants. If you attach one-inch galvanized or vinyl-coated hardware cloth to the bottom of the raised bed, moles will be effectively prevented from digging up from below.

Repellents
Use a mole repellent. According to the Washington Department of Fish and Wildlife (WDFW), there are commercially available castor oil-based repellents that have been scientifically tested on moles in the Eastern U.S. with some success. Or try this homemade repellent suggested by WDFW.

Try other commercially available products such as mechanical "thumpers" that send vibrations into the ground that supposedly encourage moles to leave. Some anecdotal evidence suggests these work for small yards, but no scientific evaluation of the products has been done.

Coexisting
The least expensive and most effective way to approach a "mole problem" is to learn to accept their presence. You can remove or tamp down molehills. Inspect your yard regularly and re-bury any exposed roots to mitigate damage to plants. You can transition your yard from a solid green mat of grass to a diverse habitat filled with native plants. The native plantings will thrive in the healthy soil that the moles have helped cultivate, and the local wildlife (including the moles) will thank you!

A Townsend's Mole feeding

A Townsend's Mole feeding while recovering at the PAWS Wildlife Center.

References

Feldhamer G.A., Thompson B.C. & Chapman J.A. (Eds). (2003). Wild Mammals of North America, Biology, Management, and Conservation (2nd ed.). Baltimore MD: The Johns Hopkins University Press.

Species at Risk Public Registry. January 11, 2016. Townsend’s Mole

Washington Department of Fish and Wildlife. January 11, 2016. Living with Wildlife: Moles