Sorex vagrans, Baird, 1858
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publication ID |
https://doi.org/ 10.5281/zenodo.6870843 |
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DOI |
https://doi.org/10.5281/zenodo.6869746 |
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persistent identifier |
https://treatment.plazi.org/id/3D474A54-A033-875F-FF25-AD171BB2F5A7 |
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Felipe |
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scientific name |
Sorex vagrans |
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Vagrant Shrew
French: Musaraigne errante / German: \Wanderspitzmaus / Spanish: Musarana errante
Other common names: Salt Marsh Shrew, Wandering Shrew
Taxonomy. Sorex vagrans Baird, 1858 View in CoL ,
“ Shoalwater Bay, W.T. [= Willapa Bay, Pa- cific Co., Washington],” USA .
Sorex vagrans is in the S. vagrans group and subgenus Otisorex along with S. ornatus . The S. vagrans group is sister to a clade including the S. palustris group, the S. sonomae group, and the S. monticolus group. Sorex orizabae has been included in S. vagrans but is considered a distinct species here. Three subspecies recognized.
Subspecies and Distribution.
S.v.halicoetesGrinnell,1913—SantaClaraCounty,WCCalifornia(SWUSA).
S. v. paludivagus von Bloeker, 1939 — Monterey County, WC California (SW USA). View Figure
Descriptive notes. Head—body 56-71 mm, tail 32-50 mm, hindfoot 12-14 mm; weight 3-9 g. The Vagrant Shrew is medium-sized. Dorsum is dull brown to grayish brown, and venter is grayish. Tail is relatively short, narrow, and either unicolored dull brown or slightly bicolored, being slightly paler below. Teeth are pigmented dark red, and pigmentation on I' occurs to the point where teeth meet, while pigmented tines are positioned above level of pigmentation on incisors. There are five unicuspids, third is smaller than fourth, and fifth is minute. Chromosomal complement has 2n = 54 and FN = 58-64.
Habitat. Most commonly open moist areas, with few trees and dense ground cover, from sea level to elevations of ¢.2100 m. Vagrant Shrews often prefer lower elevations, and in British Columbia, they are usually below 400 m. The Vagrant Shrew has been recorded in a variety of habitats, including alpine tundra, bunchgrass, wet meadows, grassy meadows, riparian zones, swamps, bogs, forest openings, and coniferous forests. They are less likely to be found in dense forests and are most common in grassy meadows, forest openings, and marshes, including salt marshes in California. They commonly colonize disturbed areas, such as cleared deciduous forests and burned forests.
Food and Feeding. The Vagrant Shrew primarily eats small invertebrates but also some plant material, seeds, and fungi. In Oregon, they eat (in descending order by volume) earthworms, spiders,crickets, caterpillars, moths, slugs, snails, June beetles and their larvae, ladybird beetles, centipedes, ants, Endogone fungi, flower parts, seeds, other vegetation, craneflies, harvestmen, aphids, moth cocoons, hemipterans, grasshoppers, bees, wasps, and other unidentified insects and insect larvae. They forage on the ground and often dig to find prey afterit is detected using scent. Seeds of trees of the pine family (e.g. Pseudotsuga , Pinus , Picea, and Abies ) are eaten, but seeds of Abies are eaten less often than the rest. Fruit and seeds of some flowering plants are also eaten, along with flowers in small quantities. In captivity, a Vagrant Shrew ate an average of 10-9 g (4-2-12-3 g) of food/ day or c.1-7 times its body weight. When attacking, Vagrant Shrews rapidly bite their prey until they are dead and then tear them apart and eat them. They seem to also feed on carrion because captive individuals have been maintained partially on carcasses of other small mammals. Vagrant Shrews occasionally eat small vertebrates, including salamanders. They cache food in times of hardship.
Breeding. Female Vagrant Shrews become reproductive in January when their uterine horns begin to increase in width; males’ testes begin to enlarge in February and remain enlarged until about August or September. Breeding can occur throughout spring until early autumn, although peak reproductive activity (births and conception) occurs in April-June. Reproduction of subspecies halicoetes occurs in February—June, peaking in April, but a few litters can be born in September. Gestation lasts ¢.21 days, and litters have 1-8 young (average c.6). Females can breed up to three times/season, and some young born early in the season can breed later in the season they were born. Very few individuals live for a second breeding season. Mortality for young is very high, ranging from 55% to 60% in the first three weeks oflife. In one study, 17% of young died in the first two days of life and 49% died in the first two weeks. Young are born hairless, weighing 0-35-0-5 g, but they quickly grow dorsal pelage by their second week. They rapidly grow in mass for the first four weeks, reaching 5-6 g. They are weaned at 16-25 days old and can stay in the nest for as long as five weeks after birth.
Activity patterns. Vagrant Shrews are active day and night, with no major peaks in activity, but periods of activity are longer throughout the night. Activity generally lasts c.5-10 minutes and is followed by a slightly longer rest period. Activity peaks more noticeably shortly after nightfall, around dawn, and in late afternoon in spring and around midnight in summer. When foraging, Vagrant Shrewsstick their noses around leaf litter and occasionally stand on their hindfeet and twitch their noses around. They often climb twigs to find their more arboreal and flying prey and use their tails in semi-prehensile ways. They also use a basic form of echolocation when foraging, emitting low-intensity but high-frequency chirps when moving around, which seems to be useful for basic navigation but inefficient for finding prey items. There are three types of nests: natal nest, resting nest, and cold-weather nest. Natal nests are dome shaped, made of dead leaves, grass, and moss and lined with fine grass or mammalian hair; they are created before a female gives birth; they can be 6-24 cm across and 2-3 cm deep; and dome shapes are generally lost as young grow. Resting nests are shallow depressions on the ground c.2—-8 cm across and are used for bouts of resting between foraging. Cold-weather nests are very similar to natal nests, although they are more rounded and oval shaped and are generally smaller. They are constructed before winter starts and used throughout the season.
Movements, Home range and Social organization. Vagrant Shrews are solitary and relatively aggressive toward intruders, often resulting in territorial feuds. Although they are very territorial, when an intruder is noticed, the defending shrew will make high-pitched aggressive chirps and charge the intruder multiple times. The intruder generally backs down, but if it does not, a fight occurs. Home ranges vary throughout the year, being largest during breeding season. Male home ranges are often more expansive than females and encompass home ranges of multiple females; during winter, their home ranges become smaller and do not overlap. In British Columbia, home ranges averaged 4343 m*for males and 2233 m?* for females; during non-breeding season, home range for both sexes averaged 1039 m®. In Washington, home ranges averaged 316 m*in April-May, 235 m?® in July-August, and 130 m? in November. Densities range from 25-8 ind/ha in late autumn and early winter to 58-2 ind/ha in summer. Nearly all individuals in winter are young that were born in the most recent breeding season; older individuals have usually died off by this point. Few individuals survive long enough to breed for more than one season. To avoid breeding with different species, odor might be used to distinguish whether an individual is of the same species or not; e.g. between Vagrant Shrews and the Montane Shrew ( S. monticolus ).
Status and Conservation. Classified as Least Concern on The IUCN Red List. The Vagrant Shrew is very widespread and common, and there are no major threats currently affecting it. Nevertheless, subspecies halicoetes and paludivagus might be threatened because of their small distributions, and halicoetes has been regarded as a species of special concern in California.
Bibliography. Brown (1974), Buchler (1976), Carraway (1989, 2007), Clothier (1955), Demboski & Cook (2001), Eisenberg (1964), Gillihan & Foresman (2004), Hawes (1976, 1977), Hennings & Hoffmann (1977), Johnston & Rudd (1957), Junge & Hoffmann (1981), Matson et al. (2016), Newman (1976), Whitaker et al. (1983).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
