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Neurotrichus gibbsiiAmerican shrew mole

By Emily Gochis

Geographic Range

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).

Habitat

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
    to 8202.10 ft

Physical Description

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
    0.28 to 0.51 oz
  • Average mass
    10 g
    0.35 oz
  • Range length
    100 to 130 mm
    3.94 to 5.12 in
  • Average length
    120 mm
    4.72 in

Reproduction

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).

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

Behavior

Shrew-moles are active both day and night, and they only sleep for one to eight minutes at a time. They stay awake for periods ranging from two to eighteen minutes long. They do not hibernate (Carraway, 1991).

Unlike other moles, N. gibbsii spend a lot of time above ground and move around easily (Wilson,1999). They are also known to be deliberate climbers, and can easily climb up low bushes in search of food or a nesting place (Dalquest, 1942).

Shrew-moles are also very good swimmers and use all of their limbs and tail to move through the water (Callaway, 1991).

Shrew-moles are gregarious and may even travel in groups that have over 11 individuals. These groups seem to move together to an area, stay there up to several days, and then move on together to another area (Dalquest, 1942).

Like other moles, N. gibbsii are fossorial and use their tunnels for both movement and hunting (Campbell, 2001). They create two different types of tunnels. The first is shallow and dug directly beneath leaf litter. The second is less common and deeper, but never below 30 cm (Yates, 1982). Shrew-moles also widen parts of their shallow tunnels to create a sleeping chamber. These chambers can be found above ground because they have a vent hole that allows the animal to breath while sleeping (Racey, 1929). These tunnels are different than those of other moles because they have open entrances, no "mole hills" and are less complex (Callaway, 1991).

Communication and Perception

Food Habits

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

Predation

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).

Economic Importance for Humans: Positive

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

Conservation Status

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

Contributors

Emily Gochis (author), University of Michigan-Ann Arbor, Ondrej Podlaha (editor), 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

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

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.

polygynandrous

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

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sexual

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

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).

References

Campbell, K. "American shrew-mole" (On-line). Accessed 10/09/01 at http://home.cc.umanitoba.ca/~rmacarth/shrewmole.html.

Carraway, L., B. Verts. 1991. Neurotrichus gibbsii. Mammalian Species, 387: 1-7.

Dalquest, W., D. Orcutt. 1942. The biology of the least shrew-mole, Neurotrichus gibbsii minor. The American Midland Naturalist, 27: 387-401.

Racey, K. 1929. Observations on the Neurotrichus gibbsii. The Murrelet, 10: 61-62.

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

Yates, T., R. Pedersen. 1982. Moles: Talpidae. Pp. 37-51 in J Chapman, G Feldhamer, eds. Wild Animals of North America. Baltimore: John Hopkins University Press.

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