| Trowbridge's shrew | |
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Eulipotyphla |
| Family: | Soricidae |
| Genus: | Sorex |
| Species: | S. trowbridgii |
| Binomial name | |
| Sorex trowbridgii Baird, 1857 | |
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| Trowbridge's shrew range | |
Trowbridge's shrew (Sorex trowbridgii) is a species of mammal in the family Soricidae. [2] It is found in southern British Columbia in Canada and in Washington, Oregon, and California in the United States. [1]
Trowbridge's shrew was first described in the scientific literature in 1857 by Spencer Fullerton Baird, in a report of surveys and explorations conducted to find a suitable route for a railroad from the Mississippi to the Pacific Ocean. [3] The scientific name given was Sorex trowbridgii. The generic name Sorex is Latin, meaning "shrew-mouse." [4] The species name "trowbridgii" is a patronym to honor William Petit Trowbridge. [4] The type locality for the species is Astoria, Oregon. Baird's initial record describes four specimens made available to him. [5] The first two were provided by Trowbridge. They were skins that had been collected by "Jas. Wayne" in June 1855. The other two specimens were collected by George Suckley at Fort Steilacoom in 1856. Those two specimens were preserved in alcohol prior to submission to Baird. [6]
Trowbridge's shrew is a medium-sized shrew with a long tail. [7] Non-breeding shrews weigh around 3.8 g (0.13 oz) while breeding shrews average around 5 g (0.18 oz). [8] The fur colorings change over the year, with a darker more brownish coat in the summer and a lighter gray in winter. [9] [7] They have many long whiskers and their ears are mostly covered with fur. Trowbridge's shrews are also known to go through two molts, one in the summer and one in the winter. [10] The winter coat is thick and grey while the summer coat is light and dark brown. [10] Young Trowbridge's shrew have a hairy tail, which becomes less hairy with age. The tail is bi-colored: darker on the top than the bottom, with a sharp line separating the colors. This feature can be used to distinguish Trowbridge's shrew from similar shrews. [7] They are pentadactyl, with whitish to lightly tan colored feet. The caps of the teeth have a dark reddish-brown pigmentation. The dental formula of Sorex trowbridgii is 1.5.1.31.1.1.3=32. [11] The skull is similar in size to that of other long-tailed shrews. [7]
Trowbridge's shrew can be distinguished from closely related shrews by the third unicuspid being smaller than the fourth. Other distinguishing features include a post-mandibular foramen, more posterior positioning of the orbit, and orientation of lacrimal and infraorbital foramina relative to the molars. [7] The Trowbridge's shrew has four traits that distinguish it from the Dusky Shrew. It has a first upper incisor that is curved, a bicoloured tail, upper unicuspid teeth have pigmented ridge separated from the cingulum by a longitudinal groove and on the first upper incisor the medial tine is above the pigmented area on the tooth. [11]
| total length (mm) | tail length (mm) | hind foot length (mm) | condylobasal length (mm) | cranial breadth (mm) | interorbital width (mm) | maxillary width (mm) | |
|---|---|---|---|---|---|---|---|
| Canadian S. t. Trowbridgii | 113 | 54 | 13 | 17.2 | 8.6 | 3.8 | 4.9 |
| American S. t. Trowbridgii | 119 | 56 | 14 | 17.4 | 8.7 | 3.8 | 4.9 |
| S. t. humboldtensis | 131 | 61 | 15 | 18.1 | 9 | 4 | 5.3 |
| S. t. monteneretensis | 123 | 52 | 14 | 18.2 | 9 | 4.2 | 5.6 |
| S. t. mariposae | 119 | 51 | 14 | 18.6 | 9.3 | 4.2 | 5.6 |
Fossilized remains of Trowbridge's shrew have been obtained from the Carpinteria Tar Pits. These dated from the Wisconsonian (late Ranchlabrean) epoch. These remains were obtained from a site at the extreme south end of the range of distribution. Scientists suspect that the shrew developed earlier, but that no fossils have been found due to a lack of such fossil sites of suitable age along the west coast north of San Francisco. [7]
Trowbridge's shrew is found along the western coast of North America. They occur in the extreme southwest of British Columbia, south of Burrard Inlet. They are found in the western part of the states of Washington and Oregon. In northern California, the distribution forks. In the west, the population continues south through the coast range to Santa Barbara County. Through eastern California, the population extends south through the Warner Mountains and the Sierra Nevada Mountains to Kern County. [7] Different subspecies are found in different regions of the geographic range. [8] They are found from sea level up to an elevation of 1,820 m (5,970 ft). [1]
Trowbridge's shrew resides in forested areas where the ground may be littered with debris for cover. [12] After logging in an area, they may remain, if sufficient ground cover is present. They are found in both dry and moist forests, as well as in swampy woodlands. Populations on Destruction Island off the Washington coast live in deep rank grass near salmonberry patches. [12] They are less likely to be found near streams. In the southern reaches of their range, they may be found in chaparral. [12]
Trowbridge's shrews occupy an important ecological niche. They are preyed upon by raptors including the barred owl (Stirix varia). [8] The Pacific giant salamander (Dicamptodon sp.) is another known predator. While domestic cats are known to kill them, they usually do not eat them. [8] Known parasites include a number of ticks, mites, chiggers, fleas, worms, and single-celled organisms. [8]
Since they are the most frequently captured shrews within their range, it is presumed that they are the most abundant. [1]
The life-span of Trowbridge's shrews is around 1.5 years. [12] They do not hibernate, but remain active year-round. They are roughly twice as abundant in the fall as in the spring. [1] Insects are a primary food source for the shrews, but they also will eat spiders, worms, and centipedes. After identifying food items in the Trowbridges Shrew's stomach, the most consumed items were centipedes (Chilopoda), spiders (Araneae), internal organs of invertebrates, slugs and snails (gastropoda) and unidentified invertebrate material. During the reproductive season, food consumption is greatest. [13] They also eat plants. Compared to other shrews in the genus Sorex, Trowbridge's shrews eat more vegetable matter. [1] During winter months, they may feed on conifer seeds, such as Douglas-fir and pine, as well as other plant seeds. [12]
Although some shrews are known to be strong swimmers, it is not clear if this is true for Trowbridge's shrew. Thus, rivers may present a barrier to dispersal of the species. [12] Additional comments about the range of Trowbdridge's shrew are extrapolated from studies on other species. [12]
As they reach sexual maturity, Trowbridge shrews gain whole body mass. Non-breeding shrews weigh around 3.8 g (0.13 oz) while breeding shrews average around 5 g (0.18 oz). The size of the testes in males increases, while the uterine horns widen in females. Once the breeding season has concluded, these structures atrophy. [8] The time of onset of sexual maturity may be earlier or later, depending on local climate conditions, with an earlier age of onset in warmer areas. [12] Males apparently reach sexual maturity two weeks earlier than females. [8]
Since pregnant females have been found, which are still lactating, it is suspected that they became pregnant while nursing the young from prior broods. The average brood size is around 3–5. [7] In northern areas, the number of embryos found in pregnant females was fewer and the breeding season appears to be shorter. The breeding season runs from March to May in Washington, but from February to June in California. [8]
Effects of logging on Trowbridge's shrew populations has been studied, but the results were inconclusive, since one study showed and increase and the other a decrease. [1]
The IUCN lists Trowbridge's shrew as "Least Concern" based on a 2008 assessment. The rationale for the listing includes an overall stable population, lack of major threats, and a widespread geographic distribution. In addition, there are protected areas throughout the area of distribution. [1]
The cinereus shrew or masked shrew is a small shrew found in Alaska, Canada, and the northern United States. This is the most widely distributed shrew in North America, where it is also known as the common shrew.
The American pygmy shrew is a small shrew found in Northern Alaska, Canada, and the northern United States, south through the Appalachian Mountains. It was first discovered in 1831 by naturalist William Cane in Georgian Bay, Parry Sound.
The Arctic shrew, also known as the blackback shrew or saddlebacked shrew, is a medium-sized shrew found in Canada and the northern United States. Separate species status has been proposed for the maritime shrew which is found in New Brunswick and Nova Scotia and had been considered to be a subspecies of the Arctic shrew. The tundra shrew was formerly considered to be a subspecies of the Arctic shrew.
The marsh shrew, also known as the Pacific water shrew, Bendire's water shrew, Bendire's shrew and Jesus shrew is the largest North American member of the genus Sorex. Primarily covered in dark-brown fur, it is found near aquatic habitats along the Pacific coast from southern British Columbia to northern California. With air trapped in its fur for buoyancy, marsh shrews can run for three to five seconds on top of the water. It measures about 16 cm (6.3 in) in length, including a 7-centimetre (2.8 in)-long tail, and weighs an average of 14.5–16 g (0.51–0.56 oz). The marsh shrew's diet consists mainly of invertebrates, which it hunts on land and in the water. They are rare; their populations are thought to be in decline, and they are considered endangered in parts of their range.
The vagrant shrew, also known as the wandering shrew, is a medium-sized North American shrew. At one time, the montane shrew and the Orizaba long-tailed shrew were considered to belong to the same species.
The genus Sorex includes many of the common shrews of Eurasia and North America, and contains at least 142 known species and subspecies. Members of this genus, known as long-tailed shrews, are the only members of the tribe Soricini of the subfamily Soricinae. They have 32 teeth.
The Eurasian pygmy shrew, often known simply as the pygmy shrew, is a widespread shrew of the northern Palearctic.
The common shrew, also known as the Eurasian shrew, is the most common shrew, and one of the most common mammals, throughout Northern Europe, including Great Britain, but excluding Ireland. It is 55 to 82 millimetres long and weighs 5 to 12 grams, and has velvety dark brown fur with a pale underside. It is one of the rare venomous mammals. Juvenile shrews have lighter fur until their first moult. The common shrew has small eyes, a pointed, mobile snout and red-tipped teeth. It has a life span of approximately 14 months.
The Eurasian least shrew, also called the lesser pygmy shrew, is the second-smallest mammal by mass after the Etruscan shrew.
Laxmann's shrew, or the masked shrew, is a species of shrew. Its range extends from northern Scandinavia and the Baltic to the Sea of Japan, including Hokkaidō, Sakhalin, and the Korean Peninsula. It favours mountain forests but is sometimes found in tundra and moorland, and also in lowland areas as well. It avoids cultivated land.
The Ussuri shrew, also known as the giant shrew, is a species of shrew found in Northeast Asia. An adult Ussuri shrew has a total length including the tail of 137 to 170 mm. It is found in valleys and on the forested slopes of mountains in the Korean Peninsula, northeastern China, and the Russian Far East. It is rarely observed, and its ecology is largely unknown.
The slender shrew is a species of shrew. An adult slender shrew has a weight of 1.5–5.3 g (0.053–0.187 oz) and a body length of 4.7–6.0 cm (1.9–2.4 in), with a tail of 4–5 cm (1.6–2.0 in); this makes it one of the smaller shrews found in its range. It is distributed across northeastern North Korea, Hokkaidō, and the Russian Far East including the Kuril Islands.
Baird's shrew is a species of mammal in the family Soricidae. It is endemic to northwest Oregon. Baird's shrew inhabits moist conifer forests.
The montane shrew is a species of mammal in the family Soricidae commonly known as the dusky shrew. Monticolus is derived from the Latin root word mons meaning mountain. It is found in Alaska, western Canada, the western United States in Washington, Idaho, Montana, Utah, Colorado, New Mexico, Arizona, Oregon, Nevada, and California, as well as in Mexico.
The ornate shrew is a species of mammal in the family Soricidae (shrews). It is endemic to western North America, ranging from Northern California in the United States to Baja California in Mexico. Eight subspecies are known, including the extinct tule shrew, known only from four specimens collected in 1905, and the Suisun ornate shrew, a species of conservation concern in California. Through skull morphology research and genetic testing on Ornate shrew populations, it has been shown that there are three main genetic subdivisions: The Southern, Central and Northern. These three genetic subdivisions of Ornate shrew arose from populations of Ornate shrews getting geographically isolated from other populations.
The Pacific shrew is a species of mammal in the family Soricidae. It is endemic to western Oregon in the United States. The Pacific Shrew is native to western Oregon, more specifically from the Siltcoos lake to the coast going from the border line of Douglas and Lane counties continuing south to the northern parts of California. The first documented Pacific shrew to be caught was found at the mouth of the Umpqua River in 1858. They are normally found in damp areas along creeks in forests and sometimes near collapsed trees. Their refuge is of the utmost importance and they are seldom found far from it. This includes collapsed trees or dense vegetation. They use the flora to build a nest, gathering small plants such as grass, moss, lichen, or leaves into a pile and pushing themselves into the middle.
The fog shrew is a species of mammal in the family Soricidae. It is endemic to northern California and Oregon in the United States.
The southeastern shrew is a species of mammal in the family Soricidae. It is found in the southeastern United States.
The New Mexico shrew is a species of mammal in the family Soricidae. It is found only in New Mexico in the Capitan and Sandia-Manzano Mountains.
The long-tailed shrew or rock shrew is a small shrew found in Atlantic Canada and the Northeastern United States.
Footnotes:
Sources:
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Media related to Sorex trowbridgii at Wikimedia Commons
Data related to Sorex trowbridgii at Wikispecies| Authority control databases: National |
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