naked mole rat, name applied to a species (Heterocephalus glaber) of small rodents found in E Africa, whose members—the only hairless rodents—live entirely in underground communities of 80 or more individuals with a structure resembling that of social-insect colonies. Colony members are closely related and seem to work for the success of the whole community rather than individual survival. The queen is head of the colony and is the only member to breed. She has approximately ten pups per litter and about four litters per year. The mole rats divide up the specialized chores, such as collecting food, disposing of waste, and digging tunnels. The colonies have extensive tunnel systems and a large central area for nesting. Naked mole rats are classified as Phylum Chordata, subphylum Vertebrata, class Mammalia, order Rodentia.

mole: see birthmark.

mole, in chemistry, a quantity of particles of any type equal to Avogadro's number, or 6.02×10²³ particles. One gram-molecular weight of any molecular substance contains exactly one mole of molecules. The term mole is often used in place of gram-molecular weight; e.g., one speaks of 18 grams of water as one mole of water rather than as one gram-molecular weight of water. The mole is a unit in the International System of Units (SI).

mole, in zoology, common name for the small, burrowing, insectivorous mammals of the family Talpidae, found throughout the temperate Northern Hemisphere. Moles are trapped as pests, although they probably do less damage than the animals they destroy, and for their fur, which is highly valued. Typical moles have rounded bodies about 6 in. (15.2 cm) long covered with soft black or gray fur; they have pointed muzzles and lack external ears. They have acute hearing and a highly developed sense of touch at the ends of their noses and tails; their tiny eyes, covered with skin or buried in fur, are sensitive to changes in light level but provide little visual acuity. Moles have short, powerful legs and extremely broad front feet, which are used as shovels and are equipped with enormous digging claws. They can move backwards almost as rapidly as forwards, and most are good swimmers. Moles tunnel just below the surface of the ground, where they hunt for food. Their tunnels make ridges and mounds in fields, gardens, and lawns; quarters for living, nesting, and wintering are in deeper burrows. A single mole can dig about 20 yd (18 m) of tunnel in a day. Moles are voracious eaters, consuming about half their own weight daily. Their diet consists mainly of earthworms and insects, but also includes small mammals such as mice; one mole may even kill and eat another when they happen to meet. They are solitary most of the year, but during the breeding season they travel in pairs. The litter, born in the spring after four weeks of gestation, consists of two to seven young. Typical species include the common European mole, Talpia europaea, and the eastern, or garden, mole of North America, Scalopus aquaticus, both about 6 in. (15.2 cm) long with a 1-in. (2.54-cm) tail. The largest moles are the western moles of North America, genus Scapanus, which may reach a length of 9 in. (22.9 cm). The smallest New World mole is the 3-in. (7.6-cm) shrew mole, Neurotrichus gibsii, of the Pacific Northwest, which resembles a shrew and prefers a forest habitat, spending much time above ground. The strangest-looking of the family is the star-nosed mole, Condylure christata, of northeastern North America, which has a ring of mobile fleshy protuberances around its snout. This mole is a good diver and leads a semiaquatic life; apparently it uses the protuberances to pick up sounds in the water. There are no true moles in the Southern Hemisphere. The golden moles of S Africa are members of the insectivorous family Chrysochloridae; they are burrowing animals with bright golden fur. There are burrowing rodents in Africa called strand moles and burrowing marsupials in Australia called marsupial moles. True moles are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Insectivora, family Talpidae.

Pigmented flat or fleshy skin mark, made up mostly of cells that produce melanin, which gives moles their light to dark brown or black colour and, in the dermis, a bluish cast. Thicker moles also contain nerve elements and connective tissue. Moles often begin in childhood, usually as flat spots between the dermis and epidermis. Those that remain there are more likely to become malignant. Most move into the dermis and become slightly raised. In children, moles may undergo changes resembling cancer but are benign. Malignant melanoma can begin in moles but almost never before puberty. During pregnancy, moles may enlarge and new ones may appear. Moles sometimes disappear with age. The term nevus refers to a congenital skin mark, whereas a mole may develop after birth. Epidermal nevi are usually the same colour as the surrounding skin.

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