Mammal Species of the World
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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 )
Global Range: Northwestern North America, from southwestern British Columbia (Fraser River region) south through western Washington (including Destruction Island), western Oregon, and western California to Fremont Peak, Monterey County. To 2440 m in Washington.
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
Length: 13 cm
Weight: 11 grams
Size in North America
Average: 114 mm
Range: 92-132 mm
Range: 9-11 g
Habitat and Ecology
It seems to be more social than other insectivores; and may travel in loose bands (Dalquest and Orcutt 1942, Maser et al. 1981). Most breeding occurs from early March to mid-May, but even then only a few percent of specimens are in breeding condition. The length of gestation not known. Litter size varies from one to four young, newborns altricial. It is reported to have an XO system of sex determination. The shrew-mole may consume more than its own body weight in food in one day. It feeds primarily on earthworms, gastropods, centipedes, sowbugs, insects, and other invertebrates. It also eats some plant seeds, fungi, and lichens. It is sightless and detects prey with its snout. It is active throughout the year.
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
Comments: Washington: moist habitats with soft earth free of sod; lower elevation ravines with deep soils, much vegetative surface litter (logs, leaves), and big-leaf maple and other plants; less commonly in lakeshore willow thickets; rarely in drier habitats (Dalquest 1948). Oregon: most common in riparian alder and alder-salmonberry thickets; less commonly occurs in mature and immature conifer, riparian hardwood, sitka spruce-salal, skunkcabbage marsh, wet pasture, headland prairie, and headland scrub habitats (Maser et al. 1981); also montane areas with low cover of lichen and few snags, and Douglas-fir forest (see Carraway and Verts 1991). California: redwood, Douglas-fir, and yellow pine forests and forest edges, usually near streams (Ingles 1965). Constructs runways near surface of duff layer and deeper but shallow burrows, usually near streams. Less fossorial than other moles.
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
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)
Comments: May consume more than its own body weight in food in one day. Feeds primarily on earthworms, gastropods, centipedes, sowbugs, insects, and other invertebrates. Also eats some plant seeds, fungi, and lichens. Sightless; detects prey with snout.
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).
- 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)
Canis lupus familiaris
This list may not be complete but is based on published studies.
Known prey organisms
This list may not be complete but is based on published studies.
Seems to be more social than other insectivores; may travel in loose bands (Dalquest and Orcutt 1942, Maser et al. 1981). Population density in favorable habitat estimated at 12-15/ha (but up to 247/ha after removal of all other small mammals) (Dalquest and Orcutt 1942).
Life History and Behavior
Perception Channels: tactile ; chemical
Comments: Active throughout the year.
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
Most breeding occurs from early March to mid-May, but even then only a few percent of specimens are in breeding condition. Length of gestation not known. Litter size varies from 1-4 young. Newborns altricial. Reported to have an XO system of sex determination.
Molecular Biology and Genetics
Statistics of barcoding coverage: Neurotrichus gibbsii
Public Records: 0
Specimens with Barcodes: 3
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1996Lower Risk/least concern (LR/lc)
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
National NatureServe Conservation Status
Rounded National Status Rank: N4 - Apparently Secure
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Relevance to Humans and Ecosystems
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
American shrew mole
The American shrew mole (Neurotrichus gibbsii) is the smallest North American 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.
It is found in damp, forested or bushy areas with deep, loose soils in northwestern United States and southwestern British Columbia. In the most northern part of its habitat, it lives along streams or moist sense woods and in the most southern part of its habitat, it is found in swampy areas that are overgrown with vegetation such as sedges or shrubs.
Like shrews, it has a pelage with guard hairs and underfur. Its fur is dense and soft. The color ranges from dark gray to a sooty bluish-black. Its tail is about half the length of its head and body. Its tail is also covered with scales and scattered coarse hairs. It has a long, flattened snout, and a short but thick, bristled tail. It is the smallest of the American moles. It is about 10 cm (3.9 in) in length including a 3 centimetres (1.2 in) tail, and weighs about 10 g (0.35 oz). It has a zygoma and auditory bullae, which are absent in shrews, but present in moles. The enamel that covers its teeth is white instead of mahogany or reddish-brown, like it is in shrews.  It also lacks a penis bone. Its front paws are smaller and do not face outwards from the body as in more fossorial moles, and so are more similar to those of shrews. The front paws are also broad with bifurcate phalanges, which provide more support for the claws in order to dig. Also, the three middle claws of the front paws are elongated and the eyes are also completely covered by skin.
In addition to the front paws, the rest of its morphological features allow it to be highly fossorial and subterranean. It has a streamlined body that allow it to move smoothly through tunnels and short appendages that are kept close to the body. It also has no ear pinnae, which is the external part of the ear. These features reduce drag when it digs and when it moves through tunnels.
Digging and Burrowing
The shrew-mole is often confused with pocket gophers, another group of fossorial subterranean mammals, because they have similar habits but they differ greatly in the methods for burrowing. Most fossorial mammals, including the pocket gophers dig with their forepaws held directly below their body, but shrew-moles dig using lateral-strokes. This method of lateral-stroke burrowing in shrew moles is an evolutionary adaptation due to the modification of the pectoral girdle and bones of the forelimbs. The pelvic girdle is small and unmodified, but the pectoral girdle contains a special joint that causes the clavicle to join with the humerus instead of the scapula. The humerus bones are unique to shrew-moles because they exist as massive rectangular shapes, unlike other fossorial mammalian groups. The humerus also has a large surface area for the attachment of well developed muscles used for digging.
The shrew-mole makes permanent tunnels by digging with its forelimbs and using its forefeet to soften the soil that will be removed to make a hollow tunnel. The tunnels form complex networks that interconnect and lead to burrows. The tunnels are rarely ever deeper than 30 centimeters below the surface, so they are not as deep as the tunnels of other mole species. The burrows are made beneath decaying leaf litter and have an opening on the ceiling that leads to the surface, which serves the purpose of ventilation. The shrew-mole also makes shallow surface runways by moving the front part of its body 45 degrees to the right and then to the left. Then back again to the right, then left, and so on. When it moves to the right, the left forepaw is thrust up rapidly lifting soil in the process and when it moves to the left, the right forepaw is thrust up to lift soil.
As the shrew-mole continues to dig through the soil, the amount of prey in the soil is significantly less than the amount present in soil that has not been dug through by them. In addition, it spends a lot of its energy to dig through the soil. Due to these factors, it is common for shrew-moles to forage through tunnels that have been dug by other shrew-moles because it is more energetically efficient and more prey might be present in tunnels that have been abandoned.
Skull and Dentition
It has a long and narrow rostrum, which is the projection that forms the snout. The junction between the skull bones turns into bone early on in their age, which makes it difficult to identify their age based on looking at their skull bones. The maxillary only turns into bone in the adults and the roots of the upper molars are exposed in immature shrew-moles. The first upper incisor is flat and it does not have an elongated crown, like shrew do. It has 36 teeth, which consist of incisors, canines, pre-molars, and molars.
Diet and Digestion
This mole is often active above ground, foraging in leaf litter for earthworms, insects, snails and slugs. It is also known to eat some vegetation such as mycorrhizal fungi and even salamanders, but earthworms are the most important food item in its diet. Its diet also depends on the type of available food sources, so it may eat more vegetation than anything else if there are no insects or other arthropods within its vicinity. It is able to climb bushes to forage for food.
Predators include owls, hawks and mustelids. Additional predators include red and gray foxes, weasels, fishers, raccoons, pine martins, and skunks. Dogs and cats can kill them as well, but do not eat them. Venomous and non-venomous snakes, bullfrogs, and opossums have also been reported to hunt them.
The most common ectoparasites found on these shrew moles are fleas and mites.
When underground shrew-moles can suffer from a low levels of oxygen, high levels of carbon dioxide, and high levels of humidity. In order to cope with these conditions, shrew-moles contain lungs that can hold large volumes and sometimes even more than 20% of their body weight.
They also experience stages of sleep that are similar to humans such as rapid eye movement sleep. It is believed that the reason why they experience stages of deep sleep is because they are subject to less danger than other mammals.
They have well developed hearing.
It can have several litters annually, except in December through January because no litter have been noted during these months. Females have litters with one to four young. Newborns are about 30 milimeters long and weigh less than 1 gram.
In females, the vagina remains sealed until follicles appear in the ovaries. In males, they lack a scrotum, but the testes and glands that associate with the testes become enlarges, which increases their weight. The fact that males lack a scrotum and the female's vagina is sealed, makes it difficult to determine the sex of shrew-moles that are not breeding without performing a dissection.
It is somewhat gregarious, which means that it lives in loosely organized communities of about 12 to 15 shrew moles. The only known type of vocalization that they produce is a faint twittering sound that can be heard for several feet. It is both diurnal and nocturnal.
Shrew-moles usually live in areas where it is difficult to cultivate so they are usually economically neutral, but there are some cases where they do damage people's homes. There are many different methods that people use for getting rid of these moles. The most common noncommercial method is trapping because it is practical for homes with little land, but unpractical for large areas of land. Other methods include catching moles by spading where a spade is put behind the mole as it creates a surface tunnel or repairs a tunnel and is then lifted up or by hand, where the mole is picked up by its fur. Chemical control agents can also be used. Using bait is another method used to control these shrew-moles. The bait usually consists of some type of cereal grain that is treated with chemicals. The type of cereal grain and chemicals used depends on the manufacturer, but a common chemical is an anticoagulant that inhibits their normal platelet function in the blood, which causes internal hemorrhaging and leads to death. Some other approaches are to force the animal away somehow or to get rid of their food source.
There are also many home remedies that are used to get rid of these shrew-moles, but whether or not these methods are successful are usually not evident. These methods include using noisemaker devices such as placing empty soft drink bottles at an angle with the bottom in the tunnel while the neck is sticking. It is believed by some that the sound that the wind produces as it goes through the bottle scares the shrew-moles away. Materials consisting of offensive and unpleasant smells and materials that cause injury are also sometimes placed in the tunnels such as broken pieces of glass, razors, exhaust fumes, moth balls, gum, and thorns.
|Wikimedia Commons has media related to Neurotrichus gibbsii.|
- Hutterer, R. (2005). Wilson, D. E.; Reeder, D. M, eds. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. pp. 303–304. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Hammerson, G. (2008). "Neurotrichus gibbsii". IUCN Red List of Threatened Species. Version 2009.2. International Union for Conservation of Nature. Retrieved 9 February 2010.
- Ronald M. Nowak, "Walker's Mammals of the World, Volume 1"
- Hartley Harrad Thompson Jackson, "A review of the American moles"
- George A. Feldhamer, Bruce C. Thompson, Joseph A. Chapman, "Wild Mammals of North America:Biology, Management, and Conservation"
Names and Taxonomy
Comments: Three subspecies (GIBBSII, HYACINTHINUS, and MINOR) were recognized by Hall (1981) and Carraway and Verts (1991).