• The Iowa Pleistocene snail (Discus macclintocki) has been around for a very long time—since the last Ice Age, or the Pleistocene, to be specific. Fossilized shells show the snails were once widespread in the U.S. Midwest. They currently have populations at about 36 sites in Iowa and Illinois.

    The small land snail is only about 6 millimeters (1/4-inch) in diameter—smaller than a dime. Its tightly coiled, dome-shaped outer shell is brown or greenish white. It lives in an unusual, temperature-controlled habitat called an algific talus slope. The rocky hillsides are cool and moist because of underground ice. Chilly air and water escape through cracks in the slope. Ground temperatures get no colder than 14° F (−10° C) in the winter and no warmer than 50° F (10° C) in the summer. That’s just the way the snails like it.

    The snails live in leaf litter on the slopes, feeding on fallen birch, maple, and dogwood leaves. During winter, they burrow underground and hibernate.

    Despite surviving for so long, the Iowa Pleistocene snail may be in jeopardy. Climate change poses a long-term threat because it could impact the steady, cool temperatures and moist environment the snail needs to survive. In addition, logging, quarrying, road building, and other human-related activities damage the snail’s habitat. Such activities risk crushing individual snails. Disturbing the land also fills in the cracks that allow the cool air and water to flow from the underground ice.

    Since 1978, the snail has been on the U.S. endangered species list. The U.S. Fish & Wildlife Service is working with state, county, and private conservation agencies to protect the snail.

    1. When was the Pleistocene?

      The Pleistocene refers to a time period that started 2.6 million years ago and ended 11,700 years ago. It was the most recent Ice Age, when large parts of the planet were covered with glaciers. During the Pleistocene, animals such as mammoths, mastodons, and saber-toothed cats roamed North America, Asia, and Europe. Around the end of the Pleistocene, all of these large creatures became extinct. Many of today’s insects, mollusks, birds, mammals, mosses, and flowering plants are closely related to genera−or even species−from the Pleistocene, including the Iowa Pleistocene snail.

    2. How do human activities, such as logging, quarrying, and road building, impact the Iowa Pleistocene snail?

      Disturbances to the land risk crushing individual snails. They also risk filling in the cracks in the slopes where cool air and water flow from underground ice, changing the habitat for the snail and other organisms.

    3. Some of the algific talus slopes where the Iowa Pleistocene snail live are part of the Driftless Area National Wildlife Refuge. How might that help the snails?   

      The U.S. Fish & Wildlife Service manages the lands that are part of the refuge. Only certain areas are open to the public, which minimizes the threat to the snails from human activities. An added benefit is that the refuge protects other species that depend on a similar habitat to survive, including another glacial relic snail called the Midwest Pleistocene vertigo and a rare plant called the northern blue monkshood. The refuge can’t protect the habitats from climate change, however.

  • Term Part of Speech Definition Encyclopedic Entry
    algific talus slope Noun

    ecosystem characterized by loose rock in a cool environment.

    climate change Noun

    gradual changes in all the interconnected weather elements on our planet.

    Encyclopedic Entry: climate change
    conservation Noun

    management of a natural resource to prevent exploitation, destruction, or neglect.

    Encyclopedic Entry: conservation
    endangered species Noun

    organism threatened with extinction.

    Encyclopedic Entry: endangered species
    fossilize Verb

    to become a solid mineral.

    habitat Noun

    environment where an organism lives throughout the year or for shorter periods of time.

    Encyclopedic Entry: habitat
    hibernate Verb

    to reduce activity almost to sleeping in order to conserve food and energy, usually in winter.

    ice age Noun

    long period of cold climate where glaciers cover large parts of the Earth. The last ice age peaked about 20,000 years ago. Also called glacial age.

    logging Noun

    industry engaged in cutting down trees and moving the wood to sawmills.

    Pleistocene Noun

    epoch lasting from about 2 million years ago to 12,000 years ago.

    quarry Noun

    site where stone is mined.

    Encyclopedic Entry: quarry
    relic Noun

    memento or surviving object of the past.