Moles are small mammals adapted to a subterranean lifestyle. They have cylindrical bodies; velvety fur; very small, inconspicuous ears and eyes; reduced hindlimbs; and short, powerful forelimbs with large paws adapted for digging.
The term mole is especially and most properly used for “true moles” of the Talpidae family in the order Eulipotyphla, which are found in most parts of North America, Asia, and Europe, although it may also refer to unrelated mammals of Australia and southern Africa that have convergently evolved the “mole” body plan. The term is not applied to all talpids; e.g., desmans and shrew-moles differ from the common definition of “mole”.
Moles are known pests to human activities such as agriculture, lawncare, and gardening. However, they do not eat plant roots; they only cause damage indirectly as they eat earthworms and other small invertebrates in the soil.
Moles have been found to tolerate higher levels of carbon dioxide than other mammals because their blood cells have a special form of hemoglobin that has a higher affinity to oxygen than other forms. In addition to this, moles utilize oxygen more effectively by reusing the exhaled air, and as a result, are able to survive in low-oxygen environments such as underground burrows.
Moles have polydactyl forepaws; each has an extra thumb (also known as a prepollex) next to the regular thumb. While the mole’s other digits have multiple joints, the prepollex has a single, sickle-shaped bone that develops later and differently from the other fingers during embryogenesis from a transformed sesamoid bone in the wrist, independently evolved but similar to the giant panda thumb. This supernumerary digit is species-specific, as it is not present in shrews, the mole’s closest relatives. Androgenic steroids are known to affect the growth and formation of bones, and a connection is possible between this species-specific trait and the “male” genitals apparatus in female moles of many mole species (gonads with testicular and ovary tissues).