E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Scapanus orarius True
Coast Mole
Family: Talpidae
Species account author: David Nagorsen
Extracted from the Opossums, Shrews and Moles of British Columbia
Photo of species

© Brian Klinkenberg  Email the photographer   (Photo ID #4497)

E-Fauna BC Static Map
Distribution of Scapanus orarius in British Columbia
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Species Information


Click on the image(s) below to view an expanded illustration for this taxon.



Illustration Source: Opossums, Shrews and Moles of British Columbia by David Nagorsen © Royal BC Museum

The Coast Mole has short, soft, velvety fur ranging in colour from blackish-brown to grey, and paler in summer. The front feet are broad and shovel-like with long, flat claws; the hind feet are not enlarged and have short, weak claws. The snout is long and almost naked. The eyes are minute; external ears are absent. The tail is short and nearly naked. Males are usually larger than females.

The skull has 44 teeth. The first upper incisor is long and broad; the other upper incisors are conical and similar in size. The auditory bullae are complete.

Identification

The only species that could be confused with the Coast Mole is Townsend's Mole (Scapanus townsendii). The two moles are similar in external appearance and cranial traits, and can only be distinguished by size. Townsend's Mole has a larger body (total length greater than 175 mm and length of the hind foot greater than 24 mm) and head (skull length greater than 37 mm and palatal length greater than 16 mm).

Dental Formula

incisors: 3/3
canines: 1/1
premolars: 4/4
molars: 3/3

Measurements

total length: 162 (145-181) n = 129
tail vertebrae: 33 (28-41) n = 121
hind foot: 21 (18-24) n = 128
weight: 69.1 (46.0-78.1) n = 16 (males)
56.6 (45.6-66.9) n = 15 (females)

Biology

Reproduction

In British Columbia, mating takes place from January to early March. Testes begin to enlarge in early January, and by May they have regressed in size. Females with embryos have been found from February to April; by May all females have given birth. The length of the gestation period is unknown. Females produce one litter a year and are capable of breeding in their first year. The average litter size is four, although females in their first year usually have only two young. Newborn young have not been observed, but presumably they are naked and lack teeth. Two young Coast Moles (13 and 15 grams) found in a nest were almost naked but had well-formed feet and tails.
Diet

Throughout its range, the Coast Mole feeds predominantly on earthworms. It also eats snails, slugs, millipedes, centipedes and various soil insects; shrew and mouse remains have been found in a few stomachs. In an analysis of the stomach contents of 108 Coast Moles trapped in British Columbia, 93 per cent contained earthworms, 2 per cent slugs, 3 per cent insects and 2 per cent unknown material. Captive Coast Moles avoided hairy caterpillars and dried or tainted earthworms. In captivity, this species can eat nearly twice its body weight in earthworms daily. Wild moles may not consume as much, but they must take extremely high numbers of earthworms. It has been estimated that a population of ten Coast Moles per hectare would eat some 219,000 earthworms per year.

Observations of caged moles suggest that this species hunts almost continuously, using its snout to locate prey by scent or touch. The mole removes soil from the prey with its front feet, then pulls the worm into its mouth, rapidly chewing and swallowing.
Natural History

The Coast Mole constructs several types of tunnels. Hunting tunnels, appearing as surface runs or ridges on the soil, are made just below the surface of the ground. The mole simply pushes the dirt to the side so there are no mounds. Usually the tunnels are used only once for hunting, dispersal or searching for a mate during the breeding season. Most activity takes place in tunnels 7 to 20 centimetres below the surface. During dry spells, tunnels one to two metres deep may be constructed. Glendenning described a Coast Mole tunnel two metres below the surface in compact sand, found during the excavation of a well at Agassiz. Tunnels are about 4 centimetres in diameter, small enlarged chambers (10 x 8 cm) occur at various intervals, often at the ends of tunnels or the junction of several tunnels. Presumably they serve as rest or nest chambers.

Soil from tunnel excavation is deposited in mounds or molehills on the surface. The molehills are smaller than those of Townsend's Mole, averaging 30 centimetres in diameter and 11 centimetres high. Digging is most pronounced in autumn and winter when the soil is moist and easy for moles to work. This is the time of year when Coast Moles may expand their range into new areas. It has been estimated that between October and March one Coast Mole can construct as many as 400 molehills. During winter, molehills of the Coast Mole are very conspicuous in fields, lawns, pastures, golf courses and grassy borders adjacent to highways.

During the breeding season, females construct nursery nests for rearing their young. Nests are situated at shallow depths (15 centimetres below the ground) where they are heated by the sun. They are about 20 centimetres across and are lined with dried grass. Nests typically have several entrances that are interconnected with runways. Unlike Townsend's Mole, there are usually no large earth mounds associated with the nursery nests.

Several researchers have suggested that this species is primarily nocturnal. However, an individual marked with a radioactive tracer and tracked with a Geiger counter was active throughout a 24-hour period with activity rhythms of about 4 hours. Subterranean movements of this animal ranged from 2 to 30 metres. The home range of the Coast Mole averages about 0.12 hectares. Population estimates for the province range from less than one mole per hectare to as high as thirteen per hectare in ideal habitats. Population numbers correlate with the physical characteristics of soil and the numbers of earthworms.

Using tooth wear as an indicator of age, Valentin Schaefer estimated that Coast Moles live three to four years in the wild. Major predators are owls, such as the Barn Owl, which generally prey on juvenile moles when they leave the breeding nest and disperse above ground in summer. In Oregon, the Rubber Boa is a predator of nestling moles. Dogs and cats are also major predators, especially during the period of juvenile dispersal. Winter and spring flooding may have a detrimental effect on some populations. During a major flood of the Fraser River in 1948, Coast Moles were observed escaping from fields and swimming to high ground. Mole populations in the flooded areas declined, but this may have resulted more from the destruction of earthworms than the direct loss of moles from drowning.

Habitat


The Coast Mole exploits a much broader range of habitats than Townsend's Mole. It prefers moist but well-drained soils, including glacial tills, clays, river deposits, and the sands and gravels of bench lands, but avoids flooded lands and acidic soils, such as peat bogs. Valentin Schaefer's research demonstrated that the greatest number of molehills occurred in loose soils with high water content and soils with large numbers of earthworms. Reduced mole activity in acidic soils probably reflects the scarcity of earthworms. Although most common in agricultural lands and riparian habitats along streams and rivers, the Coast Mole can also be found in forested areas. In British Columbia it is confined to elevations below 350 metres.

Distribution


The Coast Mole inhabits western North America from northern California to British Columbia; the eastern limits of its range are in extreme western Idaho. In British Columbia, it is restricted to the lower Fraser River valley east to Hope and north to the south shore of Burrard Inlet and the University of British Columbia Research Forest at Haney.

Taxonomy


Two subspecies are recognized. In The Mammals of British Columbia (Cowan and Guiguet 1965), British Columbian populations were assigned to the subspecies Scapanus orarius orarius True. However, in his taxonomic review of North American moles, Terry Yates classified the British Columbian populations in the subspecies Scapanus orarius schefferi Jackson, a large race that occupies eastern Oregon, Washington, western Idaho and British Columbia.

Remarks


The Coast Mole is sufficiently abundant around gardens, farms and golf courses to be regarded as an agricultural pest in the province; several commercial pest-control companies specialize in trapping moles. Although their tunnels may damage the roots of plants, much of the damage is aesthetic and the pest status of this species may be exaggerated.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS4?YellowNot Listed
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2022-09-27 6:07:31 PM]
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