The eastern mole or common mole (Scalopus aquaticus) is a medium-sized, overall grey North American mole and the only member of the genus Scalopus. Its large, hairless, spade shaped forefeet are adapted for digging. The species is native to Canada (Ontario), Mexico, and the eastern United States, and has the widest range of any North American mole.

The species prefers the loamy soils found in thin woods, fields, pastures, and meadows, and builds both deep and shallow burrows characterized by discarded excess soil collected in molehills. Its nest is composed of leaves and grasses, and its two to five young are on their own at about four weeks. Its diet consists principally of earthworms and other soil life, but the mole will eat vegetable matter.

Dogs, cats, foxes, and coyotes prey upon the mole, and the species hosts a variety of parasites. Unlike gophers, moles do not eat vegetation and pose no threat to human concerns; the occasional damage to lawns is offset by the aeration provided the soil and consumption of insects. The construction of golf courses has provided the mole with ideal habitat. The species is abundant, occurs in protected areas, faces no major threats and is of little concern to conservationists.

Description

The eastern mole is a small, sturdy animal which lives principally underground and is highly specialized for a subterranean way of life. Its body is somewhat cylindrically shaped with an elongated head. A fleshy, moveable snout projecting over the mouth with nostrils on the upper part is used as an organ of touch. The minute, degenerative eyes are hidden in the fur; the eyelids are fused and sight is limited to simply distinguishing between light and dark. The ear opening is small and concealed in the fur, but hearing is fairly acute. A short, thick tail is lightly furred and is used as an organ of touch, guiding the mole when it moves backward in the tunnel.^[3]

The very large front feet are broader rather than long with well-developed claws, and possess a specialized sesamoid bone attached to the wrist that aids digging. The front feet are normally held in a vertical position with the palms facing outward. Both the front feet and the small hind feet are fringed with sensory hairs that help the mole in its excavations. The bones of the front limbs and the breast are hugely enlarged, and provide strong support for the attached muscles used in digging. The hip girdle is narrow, permitting the mole to turn around in its tunnel by doing a partial somersault or doubling back upon itself.^[3]

The mole has grey-brown, plushlike fur with paler or browner underparts, and may appear to have a silver sheen depending on the angle it is viewed. The fur offers little resistance to backward movement in the tunnel. Compared to the female, the male tends to have a brighter orange strip on the belly being caused by secretion of skin glands in the region. Albinos occur but these may appear white, orange, or cinnamon yellow depending on the skin gland secretion. The face, feet, and tail are whitish to pink. Molting occurs in the spring and fall with the new pelage appearing first on the underparts. On the back, the new fur appears first at the tail then works forward. A distinct line usually marks the old and new fur, and there is no distinct underfur. The hairs are of equal length, and, when viewed microscopically, are seen to possess a whip-like tip unlike the hairs of any other mammal.^[3]

The sexes are determined externally by the number of openings in the groin area: the female has three – the forward one is the urinary opening (in the urinary papilla or projection), the second is the vagina, and the third is the anus at the tail. The male has two openings – the combined urinary/reproductive opening in the penis, and the anus. The testes never descend into a scrotum but remain within the body cavity. There are six teats on the belly – a pair at the chest, a pair at the groin, and a pair between the two. A rank, musky odor is emitted from a scent gland on the belly, and is left on the floor of the tunnel as the mole passes. It probably serves as a form of communication between the sexes during the breeding season, and to discourage predators. Other scent glands are found at the anus.^[3]

Measurements

The mole is about 16 centimetres (6.3 in) in length including a 3 centimetres (1.2 in) long tail and weighs about 75 grams (2.6 oz).^[4] Males collected from various parts of the species's range showed the following extremes in measurements: total length 152–184, tail 22–30, hind foot 18–21 mm, and females displayed extremes of: total length 144-16, tail 15–28, hind foot 18–21 mm, weight 40–50 grams. Males are larger than females and males collected in the northern Midwest were largest of all. Twelve adults from northeastern Florida averaged: total length 142, tail 24.5, hind foot 17.8 mm. In Hillsborough and Pasco counties in Florida, the eastern mole is still smaller, and in the area north of Tampa Bay, total length does not exceed 140 mm, and the hind foot rarely exceeds 17 mm. The smallest and darkest moles are those found in the Miami area. In Pennsylvania, specimens range in weight from 40 to 64 grams. The tooth count numbers 36 (I3/2; C1/0; P3/3; M3/3), and the diploid number is 34.^[4]

Distribution and habitat

Eastern mole range

The eastern mole is native to Canada (Ontario), Mexico, and the United States, and has the widest range of any North American mole. In the United States, the species is found from southern South Dakota and southern Wisconsin to eastern Massachusetts and south to the tip of Florida and Louisiana and west to Nebraska, Kansas, and central Texas. It is absent in the Appalachian Mountains.^[2][4]

The species is found in the southern tip of Ontario, and northern Tamaulipas, Mexico. Its distribution, however, is patchy. Colonies in southwestern Texas and Coahuila, Mexico and Tamaulipas, Mexico are isolated and small.^[2]

The species prefers well-drained, loose, sandy or loamy soil, and avoids heavy clay, stony or gravelly soils, and very dry or very wet soils. It frequents pastures, open fields, meadows, and thin woods.^[4] In some marginal areas, human activities such as the building of roads and golf courses often provide beneficial habitat due to higher quality soils and adequate moisture.^[2]

Population characteristics

In a study from 1976, home range areas of seven moles were calculated after each had been located periodically during periods ranging from 11 months to 3 years. The mean home range area was 0.74 hectares (1.8 acres); males averaged 1.09 hectares (2.7 acres), and females 0.28 hectares (0.69 acre).^[5] Because the male range is so large, males generally predominate in samples. The species' fossorial habit tends to limit its dispersal and gene flow, and soil character often limits populations. Eastern moles are good swimmers and not limited by rivers, but heavy clay soils associated with some waterways may limit dispersal.^[4]

Moles probably have a long life span due to a paucity of predators and a low reproductive rate. The young are grayer than the adults, and, with age, the skull flattens and the teeth display wear. Females live longer than males.^[3] Longevity has been estimated at 6 years with mark-recapture methods in South Carolina. In Kansas, longevity was estimated at greater than 3.5 years.^[4] The eastern mole is common in most of the United States, but populations in southern Texas and Mexico are considered extremely rare and possibly extinct.^[2]

Behavior

The species is more abundant in warm climes rather than cool or cold climes, and in the southern United States, cultivated fields will often be riddled with their burrows after a penetrating rain. The eastern mole is active at all hours with peaks in activity near dawn and at dusk. Length of time between bouts of activity average about 3 hours, but may last up to as many as 6.5 hours.^[4]

Diet

Common earthworm

The eastern mole is voracious and will daily consume food equal to 25 to 100% of its weight. In captivity, it will eat almost anything including ground beef and dog food.^[6] In its natural environment, the species principally diets on earthworms when these are available, but will eat many other foods including slugs, snails, centipedes, larval and adult insects, scarab beetle grubs, and ants at all their life stages. Vegetable matter is consumed in great quantities and Indiana specimens collected in 1974 were found to have stomachs completely filled with grass seeds.^[4]

Burrowing

The eastern mole digs both deep, permanent burrows and shallow, temporary ones just under the surface, used for foraging. The regular, permanent highway is often built 25 cm or more below the surface and is used as a retreat during hot, dry weather or when frost has descended.^[4] The oxygen levels in the tunnels can be as low as 14.3 percent and carbon dioxide as high as 5.5 percent.^[7]

Molehill

When digging new burrows, the mole will push excess soil up through vertical shafts called "molehills". New burrows just below the surface are marked by ridges and molehills, and such burrows appear to be used to facilitate the capture of earthworms and other soil life after a rain. In building burrows and probably at other times, the mole uses its nose as a tactile organ, poking about here and there. In friable soil, the species can burrow at a rate of 6 meters per hour.^[4]

The mole's nest is built of leaves and grasses, and is usually situated several inches to a foot or more below the surface. It is typically found beneath a boulder, stump, or bush, and has several approaches including one that enters from below. The eastern mole in Florida is reported to not build a nest.^[4]

Vocalizations

Moles vocalize by making high-pitched squeals, harsh, guttural squeaks, short snorting sounds, and grating the teeth.^[3]

Reproduction

Gestation is usually 45 days and a single litter of two to five young is produced between mid-April and June. In warm climates, the young may be born in March. They are born blind and naked, and are relatively large compared to the size of the mother. At ten days, they exhibit a fine, velvety light-gray fur which is retained for several weeks. Rapid growth permits the young to leave the nest and shift for themselves at about four weeks.^[4]

Survival

Dogs, cats, foxes, and coyotes are some of the predators of the species. The eastern mole harbors many parasites. One hundred four moles taken in Indiana exhibited four species of fleas, one species of sucking louse, one species of beetle, and at least twenty species of mites, several of them entirely new species with one of them, Scalopacarus, constituting a new genus.^[4]

Scientific and common names

Linnaeus

Linnaeus based the original description of the species upon a specimen found dead in the water, a fact noted on the collection label. He named the species aquaticus, certainly a misnomer because the species is the least aquatic of North American moles.^[4]

The first part of the scientific name, Scalopus, is from two Greek words which mean "digging" and "foot" (skalops, "mole", derived from the word "to dig" and pous, "foot"). The word refers to the species' large front feet which are used for digging.^[3]

The second word of the name, aquaticus, is Latin and means "found in water". The word is misleading but was given to the species because its webbed foot suggested it was accustomed to a water habitat, and the original specimen was found dead in water.^[3]

The first part of the common name, "eastern", refers to the species' range, and the second part, "mole" is from the Middle English molle which in turn is related to another Middle English word, mold-warpe, which means "earth-thrower".^[3]

Fossils

Fossil remains have been reported from the upper Ohio Valley in Pennsylvania and West Virginia, and Pleistocene cave faunas in Texas.^[6]

Interaction with humans and conservation

Cutworm

Moles till and form soil, feed on destructive insects such as cutworms and Japanese beetles, and dig tunnels that aerate the soil and permit moisture to penetrate deeper soil layers. The pelt is small and does not take dyes well; it is thus of no commercial interest to the fur industry. When moles disfigure lawns, damage the roots of garden plants while searching for food, or take sprouting corn, they are considered undesirable.^[3] In one anecdote, a homeowner reported the animal completely eradicated the Japanese beetles on his grounds.^[4]

The species is listed as Least Concern on the IUCN Red List because of its wide distribution, presumed large population, occurrence in a number of protected areas, tolerance to some degree of habitat modification, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category.^[2]

References