For Moles, a Life of Toil in the Soil

For Moles, a Life of Toil in the Soil

Illustration by Adelaide Tyrol

Two months ago a predictable eruption began on the lawn surrounding our house. Rough clumps of rich, dark subsoil appeared upon the still barren ground.

“Those **@#$&%** moles again,” my thoughts went. But moles do no lasting harm to a lawn despite making an unsightly seasonal mess.

Nevertheless these eruptions invite human attention. When our children were small, we did our mole dance, jumping up and down in an attempt to flatten the dark mounds and ridges thrust above the ground. Our ineffectual efforts never had any effect upon moles off somewhere else in their labyrinthine tunnels.

The number of mounds or surface ridges seen in a yard is no indication of how many moles are present. It may seem as though hundreds are at work, yet one mole can excavate 15 feet an hour and perhaps 35 yards in a day.

Moles are prolific. A female bears four or five young every spring in a deep nesting chamber.

When only a month old the youngsters leave home and forage on their own, so youthful exuberance may contribute to what is abundantly noticeable on lawns in early summer. Eating its own weight every day, a mole engages in a lot of hunting and a lot of excavating.

The hairy-tail mole, one of only two species of moles in Vermont and the one that inhabits our lawns, does not hibernate but lives comfortably through the winter below the frost line at a depth of about four feet. We never see its deep winter tunnels; we are conscious only of its warm-weather surface runways, or foraging tunnels, commonly seen as earthen ridges running across lawns. They are so shallow their roofs eventually collapse of their own fragile nature—or from traffic overhead.

The deeper main passageways used daily as a mole travels to and from surface feeding sites or when visiting its nest burrow tend to be permanent and inhabited by successive generations, while surface tunnels are dug afresh each year.

Excavating the lower system of burrows is not as easy as digging through loose surface soil. Deep earth has been compacted for many years, so excavating tunnels and chambers demands skill and strength. A mole’s front feet are equipped with thick webbing between the toes, a feature that caused Linnaeus over 200 years ago to believe erroneously that this purely terrestrial animal lived in water. (Vermont’s other mole, the semi-aquatic star-nosed mole, is very much at home in water.)

A mole’s shovel-like front legs – with clawed feet—emerge from powerfully muscled shoulders, perfectly suited for excavation. When making a shallow surface tunnel, a mole shoves its way forward, reaching out ahead in a kind of breaststroke. Dirt is pushed to the side, then compacted onto the tunnel walls and ceiling as the little animal pushes against it, rotating in the burrow like a furry cylindrical auger. In deeper passageways a mole turns a tight somersault in the narrow tunnel and pushes dirt to the surface through a few selected openings, depositing it on the surface like a miniature volcano—a molehill.

Maximum mole activity occurs in the morning, especially if rain has softened the soil and earthworms rise to the surface. Moles patrol their tunnels every couple of hours to see what has dropped in for dinner.

It’s the foraging surface tunnels that annoy us, but that’s where food is plentiful. Although larval and adult insects, centipedes, slugs, sowbugs and other invertebrates are abundant, the ubiquitous earthworm is the mole’s main fare. Earthworm populations are high in lawns and fields, so a mole snuffling through the soil may discover one every few inches. When it is found, the mole sniffs excitedly, digs the soil away and immediately devours it head to tail, dirt and all.

Eyes and ears are tiny and seemingly of little importance to a mole, although hearing functions well when needed. At best the degenerate eyes detect only light. But the nose is a keen dual-purpose sensory organ: it sniffs subterranean prey and is highly responsive to touch stimuli. In fact, the olfactory and tactile nose is the mole’s single most important organ for sensing its earthy environment.

You’d think that an animal living its entire life in soil would be dirty. It’s not. A mole’s velvety gray coat is the finest possible fur. It sheds dirt instantly and is smooth and clean. The hair shafts, unlike those of any other mammal, prevent soil from reaching the skin or sticking to the fur, so moles always appear free of dirt.

Despite stomping on molehills and tunnels, it’s a good bet I’ve never done in a single mole. For that I’m glad. We need to accept our hard-working subterranean neighbors and their useful, soil-aerating ways.

Bill Amos of St. Johnsbury, VT, is a retired biologist and author.

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Discussion
  1. Dr. Roberta Fiske-Rusciano → in Ewing, NJ
    Feb 05, 2011

    Dear Dr. Amos,
    Your article is very informative. I am trying to learn as much as I can about Vermont moles (not to kill them). I need to know whether the hairy-tale mole is likely to make a new tunnel in mid-winter below the permafrost? Is the gound at that depth too difficult for him because of the cold; is he more likely to wait for a thaw, meanwhile depending on the already existing system?
    Sincerely, Dr. Roberta Fiske-Rusciano

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