Scapanus orarius

Geographic Range

The range of Scapanus orarius extends from southwestern British Columbia along the western coast of Washington and Oregon, terminating in northwestern California. Coast moles can also be found in parts of eastern Washington and Oregon to the extreme east of its range into Idaho. The two subspecies of coast moles, S. o. orarius and S. o. schefferi have differing distributions: S. o. schefferi occupies eastern Washington, Oregon, and Idaho while S. o. orarious is found in the western part of Washington and Oregon.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Coast moles are fossorial animals that construct burrows in a wide variety of habitats. Unlike the closely related Townsend’s moles which are restricted to burrowing in open pastureland or scrubby forest, coast males are found in nearly every habitat within their range, excluding wet swampy ground. They even burrow in sand in close proximity to shifting dunes. Coast moles are unique in being ubiquitous in all types of forest across the Pacific Northwest - they are particularly widespread in Douglas Fir forests of the Cascades. Coast moles have also been trapped in recently logged forests, indicating their ability to adapt to disturbed habitats. Coast moles are not isolated geographically or in their habitat selection from Townsend’s moles, but will readily inhabit the same open agricultural land, sometimes with the two different species living within very close proximity of each other. Coast moles live exclusively below ground, constructing tunnels at three typical depths. Tunnels just below the surface serve as exits for dispersal or voiding excess soil in the form of molehills. Tunnels regularly used for hunting are located between 7 and 90 cm below ground. Very deep tunnels are located between 1 and 2 meters underground – it is possible that these tunnels are used to access water in subsoil.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest

• Other Habitat Features
• agricultural agricultural

Physical Description

Coast moles are adapted for lives spent exclusively underground. Their streamlined bodies are between 133 and 190 mm long and weigh between 61 and 91 grams – males are on average 4 grams larger than females and are longer by 6 to 7 millimeters. Coast moles have small, plantigrade, five-toed hind feet, while their front feet are modified into large spade shaped structures adapted for digging. The widened surface and five elongated nails push dirt behind these moles as it moves through the soil. The head is relatively flat and streamlined. The reduced, tiny eyes and lack of pinnae are further adaptations for a fossorial lifestyle. A short tail 30 to 45 mm long is present. Finally, coast moles are covered in a velvety dark grey pelage that excludes only the tail, the forelimbs, and their sensitive, naked snouts. Coast moles are divided into two subspecies: S. o. orarius is on average smaller and has a darker colored pelage than S. o. schefferi , although intergradations exist between the two subspecies where their ranges overlap in Steven’s Pass, Washington. Coast moles can be distinguished from Townsend's moles , another common mole species of the Pacific Northwest, by size. Townsend’s moles almost always have a length greater than 200 mm.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Little is known about the breeding system of Scapanus orarius since it spends nearly its whole life below ground. Coast moles breed seasonally, since dissections indicate testicular growth between the months of January and March, followed by subsequent shrinkage and a prolonged size reduction until the next year’s bout of breeding. Though normally solitary, males will dig long tunnels connecting with the territories of neighboring females during the breeding season.

Mating occurs in a 3 month interval between January and March when male coast moles experience testicular growth and construct tunnels to meet with females in neighboring territories. By May all females have given birth, but the length of gestation remains unknown. Typical litters consist of 3 to 4 pups, but it is possible that litter size increases with maternal age, meaning that females in their first breeding season only bear 1 to 2 pups. At 2 weeks old the young are naked, unweaned, and weigh between 13 and 15 grams. Weaning probably does not occur until the pups have reached a weight in excess of 40 grams – pups discovered at this stage of development have not exhibited the ability to eat on their own. Offspring become independent of their mothers by July and August. At this time juveniles disperse from their mother’s home territory and can be seen traveling above ground in search of new territories.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

As far as is known, male coast moles make no contribution to raising offspring. Young are borne and protected by the mother before weaning in a grass-lined nesting chamber about 6 inches below the surface of the ground. Beyond the construction of the nest chamber, little is known about maternal care for coast mole pups. Like all mammals, females invest heavily in their young through gestation and lactation.

• Parental Investment
• altricial altricial
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Coast moles have not been kept in captivity for extended periods of time, nor have individuals been tracked for extended periods of time throughout their lives. Age estimates are based on toothwear observed in captured specimens. A scale proposed by Schaeffer (1978) categorizes individuals as 0 to 1 years old if they have little tooth wear, 1 to 2 years old if they have some wear on the first and second molars, 2 to 3 years old if the molars are worn down to the level of the gums, and 3 to 4 years old if the canines and incisors are also worn down to the gum level. It is presumed that most individuals do not survive past the 3 to 4 year mark with such compromised dentition.

Behavior

Coast moles are solitary when not in the breeding season. Coast moles occasionally hunt aboveground in insect-rich areas around fallen logs, but spend almost their entire life underground. Coast moles alternate 5 hours of activity with about 4 hours of sleep in a repetitive cycle throughout the day and night – this behavioral activity is independent of the 24 hour night and day cycle. Coast moles will not visit all of their tunnel systems in a single active cycle, and spend most of their time in the vicinity of a nest chamber, to which they return to sleep. During the active cycle, coast moles will construct molehills as they displace dirt while searching for food items in the soil. In a year a single coast mole may produce 400 to 800 mole hills, although coast moles may not produce molehills at all in areas where soil is less compacted and easily moved. Almost all waking time is presumed to be spent searching for food, since captive coast moles deprived of food inevitably die within a few hours.

• Key Behaviors
• fossorial fossorial
• diurnal diurnal
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• solitary solitary

Home Range

Coast moles inhabit a relatively small home area in which they construct hunting and nesting tunnels. This home territory consists of a network of tunnels over an area of about 30 by 40 meters.

Communication and Perception

Coast moles rely heavily on their sense of touch to navigate their underground burrows – they are virtually blind, and their acuteness of hearing is unknown. Thire naked snouts are covered in many small bumps, each one an individual complex of sensitive nerves known as an Eimer’s organ. Coast moles will tap the ground, prey items, and other environmental objects with their snout to distinguish between them. Intraspecific communication is poorly understood, but it is likely that olfactory cues play a role.

• Communication Channels
• tactile tactile
• chemical chemical

• Perception Channels
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

The diet of coast moles varies considerably with the large number of habitats these animals can exploit. However, the majority of the diet consists of earthworms. Stomach content analyses of Scapanus orarius find earthworms in almost all individuals surveyed – furthermore, earthworms also make up more than half of stomach content by volume (Whitaker et al. 1979). The teeth of Scapanus orarius are marked by many small scratches from the soil particles present in the earthworm gut, emphasizing the prevalence of earthworms in the diet – in fact, adults eat twice their weight in earthworms each day. Coast moles also eat a variety of small terrestrial arthropods and mollusks, including centipedes, millipedes, the larvae of flies and beetles, and snails and slugs. Coast moles will ocassionaly eat vegetable matter, comprising some plant bulbs and fungi. Foraging occurs in the mole’s shallow burrow or on the surface in the vicinity of fallen logs.

• Primary Diet
• carnivore carnivore
  • vermivore

• Animal Foods
• insects
• terrestrial non-insect arthropods
• mollusks
• terrestrial worms

• Plant Foods
• roots and tubers

• Other Foods
• fungus

Predation

Owls are known to prey on coast moles when they are foraging or dispersing above ground. Bones of Scapanus orarius have been found in the regurgitated pellets of barn owls and long eared owls . The only other known predators of Scapanus orarius are the semi-fossorial rubber boas .

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

In natural ecosystems coast moles may play an important role in maintaining soil quality, aerating soil through their digging activity and aiding in soil drainage. Young coast moles during the over ground dispersal period provide a food source for owls and potentially a much wider variety of species. Scapanus orarius itself hosts an impressive array of parasitic mite species.

• Ecosystem Impact
• soil aeration soil aeration

Economic Importance for Humans: Positive

Coast moles may help control some insect pests.

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

The digging activity of coast moles can cause damage to suburban yards, golf courses and agricultural areas. Although the moles themselves do negligible damage to crops, other small rodents can use mole tunnel system to eat agriculturally important roots and tubers.

• Negative Impacts
• crop pest

Conservation Status

Coast moles are considered least concern because of their high population numbers and habitat adaptability. There are not considered significant threats to populations currently.

Additional Links

Encyclopedia of Life

Contributors

Ingrid Rochon (author), Yale University, Eric Sargis (editor), Yale University, Rachel Racicot (editor), Yale University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Carraway, L., L. Alexander, B. Verts. 1993. Scapanus townsendii. Mammalian Species , 434: 1-7.

Giger, R. 1965. Surface activity of moles as indicated by remains in barn owl pellets. Murrelet , 46: 32-36.

Gitzen, R., S. West. 2000. Occurrences of the coast moles (Scapanus orarius) in the southern Washington Cascades. Northwestern Naturalist , 81: 65-66.

Glendenning, R. 1959. Biology and control of the coast mole, Scapanus orarius orarius True, in Britsh Columbia. Canadian Journal of Animal Science , 39(1): 34-44.

Hartman, G., T. Yates. 1985. Scapanus orarius. Mammalian Species , 253: 1-5.

Marasco, P., P. Tsuruda, D. Bautista, K. Catania. 2007. Fine structure of Eimer's organ in the coast mole (Scapanus orarius). The Anatomical Record , 290: 437-448.

Maser, C., E. Brodie. 1966. A study of owl pellet contents from Linn, Benton, and Polk counties, Oregon. Murelet , 47: 319-321.

Maser, C., B. Mate, J. Franklin, C. Dyrness. 1981. Natural History of Oregon Coast mammals. U.S. Department of Agriculture Forest Service Report, PNW , 133: 1-496.

Moore, A. 1933. Food habits of Townsend and Coast moles. Journal of Mammalogy , 14: 36-40.

Schaefer, V. 1978. Aspects of habitat selection in the coast mole (Scapanus orarius True), in British Columbia. Unpublished Ph.D Dissertation, Simon Fraser University, Burnaby, British Columbia : 205.

Schaefer, V. 1982. Movements and diel activity of the coast mole Scapanus orarius. Canadian Journal of Zoology , 60: 480-482.

Silcox, M., M. Teaford. 2002. The diet of worms: an analysis of mole dental microwear. Journal of Mammalogy , 83: 804-814.

Whitaker, J., C. Maser, R. Pederson. 1979. Food and ectoparasitic mites of Oregon moles. Northwest Science , 54(4): 268-273.