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Scapanus townsendiiTownsend's mole

By David Timmer

Geographic Range

Scapanus townsendii occurs only in the Pacific Northwest region of North America. Its distribution is west of the Cascade Mountains, occurring from the northwest corner of California and continuing north through western Oregon, Washington and a few miles into southeast British Columbia. In Washington a population extends west into the Olympic Mountains and in California it is restricted to the Redwood forests on the far Northwest coast. ("COSEWIC Assessment and Update Status Report on the Townsend's Mole in Canada", 2003; Carraway, et al., 1993; Ingles, 1947; Wilson and Ruff, 1999)

Habitat

Scapanus townsendii occupies the moist lowland areas west of the Cascade Mountains. S. townsendii, like other moles, is almost exclusively fossorial. It prefers deep loamy soils and is rarely found in sandy soils. Scapanus townsendii occupies the subsurface domain of river floodplains, meadows, hayfields, pastures, residential lawns, prairies, and some fir forests. The Olympic Mountain population, S. townsendii olympicus, resides in an alpine habitat of grasses, sedges, alpine wildflowers, and subalpine fir forests.

Sympatric with S. townsendii, coast moles (Scapanus orarius) prefer drier soils that are better drained, sandier, and less likely to flood. ("COSEWIC Assessment and Update Status Report on the Townsend's Mole in Canada", 2003; Carraway, et al., 1993; Ingles, 1965; Verts and Carraway, 1998; Wilson and Ruff, 1999)

  • Range elevation
    0 to 1900 m
    0.00 to 6233.60 ft

Physical Description

Scapanus townsendii is the largest mole in North America. Its pelage is purplish-gray to black and has a metallic appearance. Members of this species range in weight from 100 to 170 g, and are between 179 and 237 mm in total length. Males tend to be larger than females.

Its obvious characteristics are those that make it supremely adapted to a fossorial lifestyle. Its body is cylindrical and streamlined. The fur is short and able to bend easily in any direction. Its nostrils open upwards, its eyes are reduced, and its ears are reduced to the point that they are not externally visible. Perhaps the greatest digging adaptation of this species is its broad shovel-like front forepaws. They are as wide as they are long, and the digits have large claws. The pectoral girdle that supports the front limbs allows the limbs to rotate ventrally for more efficient digging. The humerus is broad and square-shaped and it articulates with the clavicle. Its hindfeet are much smaller and have shorter claws. Its tail is short and mostly naked, sparsely covered with course hairs.

Scapanus townsendii can be distinguished from other sympatric moles mainly by its large size. It is all-around larger and has a more prominent sublachrymal ridge than Scapanus orarius. Unlike Scapanus latimanus, its pelage has a metallic luster. It has wider forefeet and more teeth (44 instead of 36)than Neurotrichus gibbsii. ("COSEWIC Assessment and Update Status Report on the Townsend's Mole in Canada", 2003; Carraway, et al., 1993; Ingles, 1965; Nowak, 1997; Wilson and Ruff, 1999)

  • Sexual Dimorphism
  • male larger
  • Range mass
    100 to 170 g
    3.52 to 5.99 oz
  • Average mass
    130 g
    4.58 oz
  • Range length
    179 to 237 mm
    7.05 to 9.33 in
  • Average length
    205 mm
    8.07 in

Reproduction

Townsend’s moles are polygynandrous. Their fossorial habits have made it difficult to observe mating behavior, so not much is known about their reproductive behavior. It is thought that during the breeding season, males leave their permanent tunnels and construct temporary tunnels throughout the surrounding areas to look for females. Little is known about how males compete with each other for mates. Captured females have been observed to have vaginal plugs, deposited by males, likely to prevent other males from mating with them. This observation indicates that females mate with multiple males. ("Wildlife in British Columbia at Risk: Townsend's Mole", 1999; Carraway, et al., 1993)

Scapanus townsendii breeds once per year between November and February. Males in Oregon have been captured in breeding condition with enlarged testes as early as November. The breeding period peaks in January and February.

Females give birth to an average of 3 offspring per litter. Young moles are born in late March or Early April, 4 to 6 weeks after mating. Young are atricial but develop rapidly. Moles weigh about 5 grams and are born pink and without fur. At birth, they lack recognizable eyes, and the claws are not yet hardened. An interesting characteristic of the neonates is the already oversized front limbs. They begin to grow fur after 22 days, and have a complete coat by 30 days. By the time they are fully furred, young moles weigh between 60-80 grams. The young moles stay in the nest for 30 to 36 days and then they begin to disperse. Moles disperse throughout the surrounding areas depending on population density and habitat availability. Moles are reproductively mature at about 10 months of age. ("COSEWIC Assessment and Update Status Report on the Townsend's Mole in Canada", 2003; "Wildlife in British Columbia at Risk: Townsend's Mole", 1999; Carraway, et al., 1993; Verts and Carraway, 1998; Wilson and Ruff, 1999)

  • Breeding interval
    Townsend's moles breed once yearly.
  • Breeding season
    Breeding occurs from late December through early March.
  • Range number of offspring
    1 to 4
  • Average number of offspring
    3
  • Range gestation period
    4 to 6 weeks
  • Range time to independence
    30 to 36 days
  • Average age at sexual or reproductive maturity (female)
    10 months
  • Average age at sexual or reproductive maturity (male)
    10 months

S. townsendii males show no signs of parental care. Females build one of the most extensive nesting chambers of any North American Talpid. The large nesting chamber is generally constructed about 20 cm below the surface of the ground. Nesting chambers are often constructed in undisturbed areas, such as under fencerows. The chambers are often elevated from other portions of the burrow system, which prevents flooding and helps to take advantage of solar radiation. The female lines the nesting chamber with grasses, leaves, and moss, which she replaces periodically. The nesting chamber has several exit tunnels. Some have been found to have up to 11 exits. The presence of the nesting chamber is often given away from above by a huge mound up to 76 cm in diameter and 46 cm high, or by a ring of several smaller mounds. The female defends the chamber and young from intruders. The young disperse from the nest 4 to 6 weeks after birth and after this future contact with the parents is rare. ("Wildlife in British Columbia at Risk: Townsend's Mole", 1999; Wilson and Ruff, 1999)

  • Parental Investment
  • no parental involvement
  • altricial
  • female parental care
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Actual lifespan has not been documented. It is thought that S. townsendii has a ifespan similar to that of the closely related species, Scapanus orarius. If this is so, these moles live an average of 3 breeding seasons. ("COSEWIC Assessment and Update Status Report on the Townsend's Mole in Canada", 2003)

Behavior

Townsend’s moles are almost exclusively fossorial. Individuals construct a permanent tunnel system, which they use to move around their territory and routinely patrol for earthworms and insects that have fallen into the tunnels. These permanent tunnels are generally constructed 15 to 20 cm below the surface of the earth. They also construct shallow feeding tunnels which are often apparent from the surface. These can range from 1 to 10 cm below the surface, and are likely only used once while searching for prey. During the breeding season they may also construct these shallow tunnels to search for mates. Additionally, they sometimes build deep tunnels, reaching depths of up to 3 m, in order to travel under roads or buildings. These deep tunnels have been found to be used by more than one individual.

The amount of soil that is excavated by S. townsendii is impressive. While constructing and maintaining their tunnel systems, they push excess soil to the surface to get it out of the way. This is done using their forefeet like a bulldozer blade to push the soil to the surface. These mounds are ubiquitous in areas where the moles are active. The mounds created by S. townsendii are conical and reach an average height of 17 cm and an average diameter of 43 cm. These mounts are distinguishable from those made by Scapanus orarius, as the latter species make much smaller mounds. Scapanus orarius also does not create as many mounds in a given area. Scapanus townsendii has been observed to create an immense number of mounds in an area. One male was found to have created 302 mounds in 77 days. Mound density has been observed to reach 805/hectare in a densely populated field. Much of the excavation activity occurs in the spring when the soil is moist. During this time an individual mole can produce on average 4 mounds per day.

Scapanus townsendii is generally though to be nocturnal. However, there have been diurnal observances of mole activity leading some to believe they are active throughout the day with intermittent sleeping periods. Moles have been found in owl pellets indicating some above-ground nocturnal movement, probably by dispersing juveniles. They have also been observed as roadkill, likely for this same reason.

Scapanus townsendii is generally solitary and territorial. Populations of moles often inhabit a similar area but out of breeding season they avoid each other. They aggressively defend their territories from intruders. During the breeding season, individuals are more likely to come into contact as they search the surrounding areas for mates. Territories they encounter are scent-marked, either welcoming or warning intruders. The considerable energy and effort required to build and maintain their tunnel systems likely lead moles to also put considerable effort into securing their homesites.

How the individuals allocate territory sites and develop social structures within populations is not documented because of the difficulty of observing below-ground behavior.

Moles often leave their territories for mating and during flood events. The lowland habitats they inhabit can often be prone to seasonal flooding. To espace flooding, they often burrow ahead of flood waters as long as they can until they are forced aboveground by the water. Being fairly proficient swimmers, they can also sometimes swim to higher ground. Flooding often kills many moles, but those that survive are usually able to quickly return to their territories once the waters recede. Territories that are not reinhabited are often overtaken by surviving moles. ("COSEWIC Assessment and Update Status Report on the Townsend's Mole in Canada", 2003; "Wildlife in British Columbia at Risk: Townsend's Mole", 1999; Carraway, et al., 1993; Giger, 1973; Hoefler and Harris, 1990; Wilson and Ruff, 1999)

  • Range territory size
    30 to 10400 m^2
  • Average territory size
    1700 m^2

Home Range

Individual home ranges are dependent on habitat quality and availability. Territories have been found to average 0.17 ha (0.42 acre). Moles can live quite densely in high quality habitats. In Tillamook County, Oregon 12.4 moles/acre were found in high quality habitat, but only 0.42 moles/acre were found in low quality habitat. High quality habitat is often agricultural fields which are fertilized with solid manure. These areas generally have abundant earthworm populations. Low quality habitats are poorly drained areas where earthworms can not survive.

Dispersing juveniles in Oregon moved an average of 600 feet from their birthsite. One male was found to have dispersed nearly 3,000 feet. Some of this movement takes place aboveground and leaves the mole vulnerable to predation and other danger. (Giger, 1973; Hoefler and Harris, 1990)

Communication and Perception

The primary method of perception for S. townsendii is its sense of touch. It has sensitive vibrissae on its snout with which it accurately perceives its nearby surroundings. Because of its subterranean lifestyle, its sense of sight is not necessary. Its highly reduced eyes can apparently only detect light intensity and not individual shapes. The senses of smell and hearing are also secondary in this species. Chemical cues are used to mark territories, and indicate mating availability. Abandoned territories are often overtaken when scent-marking chemicals lose their potency. ("COSEWIC Assessment and Update Status Report on the Townsend's Mole in Canada", 2003; Giger, 1973)

Food Habits

Scapanus townsendii primarily eats soil-dwelling invertebrates. Earthworms comprise the majority of its diet. Several studies have found earthworms encompassing more than 70% of its diet. The rest of its diet consists of differing percentages of other invertebrates, including insect larvae, centipedes, snails, and slugs, ad well as a small percentage of plant tubers, and bulbs. Interestingly, the large earthworms that it primarily eats were likely introduced from Europe more than 200 years ago. These are from the family Lumbricidae, such as Lumbricus terrestris. Historically, the moles likely ate more insect larvae than they do now. Studies have found small amounts of shrew and mouse matter in examined stomachs.

The teeth of S. townsendii are specialized for breaking up the tough exoskeletons of insects. The tunnel system operates as an efficient trap for worms, larvae, and other invertebrates that drop into it and are then captured by the patrolling mole. S. townsendii is a voracious feeder. Individual moles often consume more than 50% of their body weight and up to 1.5 times their body weight in a single day.

Scapanus townsendii is the only western mole documented to eat underground plant material. Because of this, tulip, iris, potato, and carrot farmers expend great amounts of energy getting rid of S. townsendii if they are found in their fields. ("COSEWIC Assessment and Update Status Report on the Townsend's Mole in Canada", 2003; "Wildlife in British Columbia at Risk: Townsend's Mole", 1999; Carraway, et al., 1993; Moore, 1933)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms
  • Plant Foods
  • roots and tubers

Predation

Because they are almost exclusively fossorial, Townsend’s moles are relatively safe from predators. Adults are rarely captured by raptors or carnivores. Those moles that do end up as prey items are usually dispersing juveniles. This is when they are more likely to be moving above-ground. Raptors such as red-tail hawks, great horned owls, and barn owls have been known to eat S. townsendii. Carnivores such as coyotes (Canis latrans) and weasels (Mustelidae) will also prey on these moles. Domestic animals often kill S. townsendii. Dogs and cats often kill moles but do not eat them. Cows often inadvertently trample moles or their nesting chambers.

Scapanus townsendii has a fairly potent odor. This odor is thought by some to be an anti-predator adaptation that makes them unpalatable.

Humans are more likely than are other animals to kill S. townsendii. Townsend’s moles are often considered pests because of the mounds they excavate, and the small amounts of vegetable material they consume. Golf course owners, farmers, and urban residents who desire well-manicured lawns are perhaps the greatest mole predators. ("COSEWIC Assessment and Update Status Report on the Townsend's Mole in Canada", 2003; Carraway, et al., 1993; Ingles, 1947)

Ecosystem Roles

Scapanus townsendii is a secondary consumer. It is both a predator and a prey species. It is a major predator in its subterranean environment, eating a substantial biomass of soil-dwelling invertebrates and ecosystem components. Scapanus townsendii, while not a significant prey species, is a minority food source for some predators.

The impact of S. townsendii on the soil ecosystem is significant. This species is an influential physical engineer of the soil ecosystem. The amount of soil moved around and paddled through by S. townsendii is extensive. Because of their movements and activities, they mix and aerate soil. They influence many aspects of the local environment: decomposition, fertilization, physical structure, and hydrology.

Their predator pressure on insect larvae and earthworms helps to keep these populations in check. Also, this pressure undoubtedly acts as an evolutionary driving force for these prey species.

The extensive tunnel systems of S. townsendii also act as communal runways for many other mammals. Voles Microtus townsendii, Microtus oregoni, mice Mus musculus, Peromyscus maniculatus, and shrews Sorex spp frequently use mole tunnels as runways. Other mammals that have been observed using mole tunnel system are ground squirrels, gophers, and rats.

Townsend’s moles have been found to host many ectoparasite species, including several species of chiggers, fleas, and ticks. (Carraway, et al., 1993)

Commensal/Parasitic Species
  • Several species of chiggers, fleas, and ticks

Economic Importance for Humans: Positive

Scapanus townsendii has a considerable positive economic impact on humans. Members of this species prey on a significant amount of invertebrate pests. They keep in check many insect pests that are damaging to agricultural crops and lawns by eating them or their larvae. They also substantially aerate, fertilize, and mix soil layers, increasing productivity and soil health.

Finally, because they are considered a pest species the control of moles provides economic benefit in the form of jobs and research. This becomes readily apparent when observing the abundance of literature available from extension agents and pest control companies on the best methods and techniques for controlling mole populations. (Carraway, et al., 1993)

  • Positive Impacts
  • research and education
  • produces fertilizer
  • controls pest population

Economic Importance for Humans: Negative

Scapanus townsendii is held responsible for large amounts of economic damage to commercial bulb growers, cattle ranchers, golf course managers, and suburban lawn owners. Their burrowing activity can push up roots leaving them exposed and desiccated, their mounds can cover plants, and they are one of the only moles that is known to eat some plant material – including bulbs and tubers. Additionally, hundreds of homeowners go to various extremes to get rid of the moles from their lawns when the mounds first begin appearing. For all these vested interests, a great amount of finance and personal energy is expended each year in repelling, trapping, capturing, and poisoning Townsend’s moles. All of these are generally only a temporary fix, as moles will reestablish an area if the habitat is suitable. Eradication is not possible, either finacially or naturally.

One early example that calculated the economic damage of S. townsendii was documented in 1961. This study attributed more than $100,000 in annual economic damage to one dairy farm in Tillamook Co., Oregon. This damage was calculated by estimating: forage loss to cattle, equipment damage, the decreased the value of silage, and drying of plant roots. They were also found to be indirectly responsible for damage done by other rodents that use the mole’s tunnels as runways for access to plant material.

Even though their activities are often in conflict to human economic interests, the damage of S. townsendii is somewhat counteracted by it beneficial activities of preying on insect pests and increasing soil health. (Carraway, et al., 1993)

  • Negative Impacts
  • crop pest

Conservation Status

Throughout its range S. townsendii is fairly common as is evident by the conspicuous and numerous mounds seen where the moles are found. Human land management activities over the past 200 years have likely increased its favored habitat. The clearing of dense forest, the creation of hayfields and pastures, the spreading of manure, and the introduction of the large earthworms from Europe have expanded suitable habitat for the mole and probably increased its numbers from what they were before European settlement.

Because of its relatively limited distribution, there is some interest in monitoring Townsend's mole populations. In Canada, where its distribution only extends a few miles across the international border into southeast British Columbia, S. townsendii was listed as endangered in May 2003. There is a single population in Canada with perhaps only about 450 individuals. This population is under threat because of urbanization, habitat fragmentation, and pest removal activities. ("COSEWIC Assessment and Update Status Report on the Townsend's Mole in Canada", 2003; "Wildlife in British Columbia at Risk: Townsend's Mole", 1999)

Other Comments

Historically, mole skins were extensively marketed. Throughout the 17th, 18th, and 19th centuries mole skins were used for capes, trimmings, purses, and tobacco pouches. As late as the 1920’s they were still being trapped for their fur. After World War I, the mole skin business was extremely lucrative and a skin of S. townsendii was fetching between $0.50-0.60. By the mid-1930’s there was no longer a demand or a market for mole skins. (Hamilton Jr., 1939)

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

David Timmer (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

soil aeration

digs and breaks up soil so air and water can get in

solitary

lives alone

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Committee on the Status of Endangered Wildlife in Canada (COSEWIC). COSEWIC Assessment and Update Status Report on the Townsend's Mole in Canada. 0-662-33588-0. Ottawa: Environment Canada. 2003.

British Columbia, Ministry of Environment, Lands, and Parks. Wildlife in British Columbia at Risk: Townsend's Mole. 0-7726-7669-0. Victoria: Wildlife Branch. 1999.

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

Giger, R. 1973. Movements and Homing in Townsend's Mole near Tillamook, Oregon. Journal of Mammalogy, 54:3: 648-659.

Hamilton Jr., W. 1939. American Mammals. New York: McGraw Hill Book Company.

Hoefler, G., J. Harris. 1990. "California Wildlife Habitat Relationships System" (On-line). Townsend's Mole. Accessed February 24, 2004 at http://www.dfg.ca.gov/whdab/html/M016.html.

Ingles, L. 1947. Mammals of California. Stanford: Stanford University Press.

Ingles, L. 1965. Mammals of the Pacific States. Stanford: Stanford University Press.

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

Nowak, R. 1997. "Walker's Mammals of the World Online 5.1" (On-line). Accessed March 02, 2004 at http://www.press.jhu.edu/books/walkers_mammals_of_the_world.

Verts, B., L. Carraway. 1998. Land Mammals of Oregon. Berkeley: University of California Press.

Wilson, D., S. Ruff. 1999. Smithsonian Book of North American Mammals. Washington DC: Smithsonian Institution Press.

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