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Brief Summary

    American shrew mole: Brief Summary
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    The American shrew mole (Neurotrichus gibbsii) is the smallest species of mole. It is the only living member of the genus Neurotrichus and the tribe Neurotrichini. It is also known as Gibb's shrew mole and least shrew mole. It is not closely related to the Asian shrew mole (Uropsilus in Urotrichini). The reason that it is called a "shrew mole" instead of being called either a "shrew" or a "mole" is because of its fur, which is a characteristic of shrews and its large head and heavy dentition, which is characteristic of moles.

Comprehensive Description

Distribution

    Distribution
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    Neurotrichus gibbsii is found in western North America, from mid-California to lower British Columbia. It ranges from the Pacific Ocean to the Cascade and Sierra Nevada mountains. Shrew-moles are also found on Destruction Island, Washington (Campbell, 2001).

    Biogeographic Regions: nearctic (Native )

Morphology

    Morphology
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    N. gibbsii is the smallest species of New World Talpidae (Wilson and Ruff, 1999). Its hair is black or blue-black and not as plush as other moles (Dalquest, 1942). Shrew-moles' forefeet are slightly broadened, not webbed and modified for digging only (Wilson and Ruff, 1999). The external ears are absent. Eyes are greatly reduced, and these animals have a flat, elongated nose (Carraway, 1991). The tail is about half as long as the body and reasonably wide (Reed, 1951). N. gibbsii show no sexual diamorphism and its dental formula is 3/3, 1/1, 2/2, 3/3= 36 (Carraway, 1991).

    Range mass: 8 to 14.5 g.

    Average mass: 10 g.

    Range length: 100 to 130 mm.

    Average length: 120 mm.

    Other Physical Features: endothermic ; bilateral symmetry

Habitat

    Habitat
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    N. gibbsii prefer soils that are easy to dig, and where there is plenty of organic matter. They are mostly found in the temperate rainforests of northwest North America, where soils are soft and deep. Shrew-moles can also be found in areas that are moist and weedy or brushy (Campbell, 2001).

    Range elevation: sea level to 2500 m.

    Habitat Regions: temperate

    Terrestrial Biomes: rainforest

Trophic Strategy

    Trophic Strategy
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    N. gibbsii need a lots of food, compared to thier body size, because of their high metabolism. Dalquest (1942) observed that shrew-moles are capable of eating up to 1.4 times their own body weight in twelve hours and can die of starvation very quickly. He also observed that they use their nose to locate prey. He describes the process of a Shrew-mole walking up to the prey and "rapping" its nose on the ground right in front of the prey, then turning its head to the right and rapping on the ground again. It will repeate this motion, but turning its head to the left. These motions are repeated very quickly until the shrew-mole's nose touches the prey. Shrew-moles also use their long noses to push over insect pupae and isopods (Dalquest, 1942). N. gibbsii capture earthworms and other prey when they fall into the tunnels they dig. Earthworms are their prefered food (Yates,1982).

    Foods eaten include: earthworms, insect larvae, snails, slugs, centipedes, sow bugs, fungus and seeds.

    Animal Foods: insects; terrestrial non-insect arthropods; mollusks; terrestrial worms

    Plant Foods: seeds, grains, and nuts

    Primary Diet: carnivore (Vermivore)

Associations

    Associations
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    Dalquest (1942) observed that if a Shrew-mole is scared into hiding, it will reemerge in search of food in less than a minute. This makes them an easy target for predators, though they are not the major diet of any species (Racey,1929). Owls seem to be their biggest predator (Carraway, 1991).

    Known Predators:

    • owls (Strigiformes)
    • snakes (Serpentes)
    • red-tailed hawks (Buteo jamaicensis)
    • raccoons (Procyon lotor)
    • swift foxes (Vulpes velox)
    • coyotes (Canis latrans)
    • domestic dogs (Canis lupus familiaris)
    • domestic cats (Felis silvestris)
    • gray foxes (Urocyon cinereoargenteus)
    • red foxes (Vulpes vulpes)

Behavior

    Behavior
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    Perception Channels: tactile ; chemical

Reproduction

    Reproduction
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    Mating System: polygynandrous (promiscuous)

    Shrew-mole has a relatively long breeding season. Reproduction happens once a year and lasts from late February to August. The length of the gestation period is unknown, but is assumed to be at least four weeks long (Yates, 1982). The nests are built above ground, although one nest was observed in a stump about a meter off the ground (Dalquest, 1942). The babies are born blind and weigh less than a gram (Wilson and Ruff, 1999).

    Breeding season: usually lasts from late February to August

    Range number of offspring: 1 to 4.

    Average number of offspring: 3.

    Average gestation period: unknown minutes.

    Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual

    Parental Investment: altricial ; female parental care

Conservation Status

    Conservation Status
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    American Shrew-moles are described to be "common" throughout their range (Wilson and Ruff, 1999).

    US Federal List: no special status

    CITES: no special status

    IUCN Red List of Threatened Species: least concern

Benefits

    Benefits
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    N. gibbsii do have an effect on controlling bark beetles and other harmful insects in their own habitats. But this is of minimal economic benefit, because most areas where the shrew-mole is found are bad sites for logging or farming (Dalquest, 1942).

    Positive Impacts: controls pest population