The American shrew mole (''Neurotrichus gibbsii'') is the smallest species of

mole Mole (or Molé) may refer to: Animals * Mole (animal) or "true mole", mammals in the family Talpidae, found in Eurasia and North America * Golden moles, southern African mammals in the family Chrysochloridae, similar to but unrelated to Talpida ...

. It is the only living member of the genus ''

Neurotrichus ''Neurotrichus'' is a genus of shrew-like moles. It is classified, together with the fossil genus '' Quyania'', in the tribe Neurotrichini of the subfamily Talpinae. The only living species is the American shrew-mole (''N. gibbsii'') of the n ...

'' and the tribe

Neurotrichini Neurotrichini is a tribe within the subfamily Talpinae of the mole family. It includes the living genus '' Neurotrichus'' with a single living species, the American shrew-mole (''Neurotrichus gibbsii''). While today restricted to the New World, f ...

. 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 Urotrichini is a tribe of the mole family, and consists of Japanese and American shrew-moles. They belong to the Old World moles and relatives branch of the mole family (Talpidae). There are only two species, each of which represents its own g ...

). 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.Ronald M. Nowak
"Walker's Mammals of the World, Volume 1"
/ref>

Habitat

It is found in damp, forested or bushy areas with deep, loose soils in the northwestern United States and southwestern

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

. In the most northern part of its habitat, it lives along streams or moist dense woods and in the most southern part of its habitat, it is found in swampy areas that are overgrown with vegetation such as

sedges The Cyperaceae are a family of graminoid (grass-like), monocotyledonous flowering plants known as sedges. The family is large, with some 5,500 known species described in about 90 genera, the largest being the "true sedges" genus ''Carex'' wit ...

or shrubs.Hartley Harrad Thompson Jackson
"A review of the American moles"
/ref>

Morphological features

Like shrews, it has a

pelage Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket ...

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 in length including a tail, and weighs about . It has a

zygoma The term zygoma generally refers to the zygomatic bone, a bone of the human skull commonly referred to as the cheekbone or malar bone, but it may also refer to: * The zygomatic arch, a structure in the human skull formed primarily by parts of the ...

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

shrew Shrews (family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to differ ...

s. The front paws are also broad with bifurcate phalanges, which provide more support for the claws in order to dig.George A. Feldhamer, Bruce C. Thompson, Joseph A. Chapman
"Wild Mammals of North America:Biology, Management, and Conservation"
/ref> 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 Pocket gophers, commonly referred to simply as gophers, are burrowing rodents of the family Geomyidae. The roughly 41 speciesSearch results for "Geomyidae" on thASM Mammal Diversity Database are all endemic to North and Central America. They are ...

, 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

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 The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists of ...

and bones of the

forelimbs A forelimb or front limb is one of the paired articulated appendages (limbs) attached on the cranial (anterior) end of a terrestrial tetrapod vertebrate's torso. With reference to quadrupeds, the term foreleg or front leg is often used instead. ...

. The

pelvic girdle The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The p ...

is small and unmodified, but the

contains a special joint that causes the

clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the r ...

to join with the humerus instead of the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...

. 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 Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

, 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

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...

ry only turns into bone in the adults and the roots of the upper molars are exposed in immature shrew-moles. The first upper

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

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 Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavi ...

in leaf litter for

earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class G ...

s 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, although that is not its main eating resource. Like all shrew-moles, the stomach size of this shrew mole in inversely proportional to its body weight. Their intestinal tract is quite short and digestion occurs rapidly.

Predators

Predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

s include

owl Owls are birds from the order Strigiformes (), which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers a ...

s, hawks and

mustelid The Mustelidae (; from Latin ''mustela'', weasel) are a family of carnivorous mammals, including weasels, badgers, otters, ferrets, martens, minks and wolverines, among others. Mustelids () are a diverse group and form the largest family ...

s such as weasels, fishers, and pine martins. Additional predators include red and gray foxes, raccoons, 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. The endoparasites found in shrew-moles consist of twenty species of coccidian

protozoans Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

, at least five species of nematode, two species of

trematode Trematoda is a class of flatworms known as flukes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is usually a snail. The definitive h ...

, and two species of

acanthocephalan Acanthocephala (Greek , ', thorn + , ', head) is a phylum of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses to p ...

Physiology

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.

Genetics

The shrew-mole has 38 chromosomes. The sex chromosomes are XX in females and XY in males. The Y chromosome in males is very small and appears to be similar in all species.

Reproduction

It can have several litters annually, though no litters have been recorded between December and January. Females have litters with one to four young. Newborns are about 30 millimeters long and weigh less than 1 gram. In females, the vagina remains sealed until follicles appear in the

ovaries The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...

. Males lack a scrotum, but the testes and associated glands become enlarged, which increases their weight. These characteristics make it difficult to externally determine the sex of shrew-moles.

Social behavior

It is somewhat

gregarious Sociality is the degree to which individuals in an animal population tend to associate in social groups (gregariousness) and form cooperative societies. Sociality is a survival response to evolutionary pressures. For example, when a mother wasp ...

, 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.

Economic status

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 non-commercial 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 A spade is a tool primarily for digging consisting of a long handle and blade, typically with the blade narrower and flatter than the common shovel. Early spades were made of riven wood or of animal bones (often shoulder blades). After the a ...

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.

References

{{Taxonbar, from=Q469953 Talpidae Mammals described in 1858 Taxa named by Spencer Fullerton Baird Endemic fauna of the Pacific Northwest