Sorex trowbridgii Baird 1858
Creators: name: Mittermeier, Russell A.
name: Wilson, Don E.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Soricomorpha
Soricidae
Sorex
Sorex trowbridgii
Sorex trowbridgu

description: 33. Trowbridge’s Shrew <i>Sorex trowbridgu</i> <b>French:</b> Musaraigne de Trowbridge / <b>German:</b> Trowbridge-Spitzmaus / <b>Spanish:</b> Musarana de Trowbridge <b>Taxonomy.</b> Sorex trowbridgii Baird, 1858, “ Astoria [Clatsop Co.], Oregon.” Placement of S. trowbridgui is currently uncertain, but itis included as the only member of the trowbridgii group, which seems to be a separate lineage of Sorex close to the saussurei group. It is not currently assigned to either of the recognized subgenera but might require a new subgenus to hold it and the other unplaced groups (merriami group, saussurei group, salvini group, and veraepacis group). Five subspecies recognized. <b>Subspecies and Distribution.</b> S.t.trowbridgiiBaird,1858—SWBritishColumbia(SWCanada),WWashington,WOregon,andNWCalifornia(USA). S.t.destructioniScheffer&amp;Dalquest,1942—DestructionI,offNWWashington(NWUSA). S.t.humboldtensisH.H.T.Jackson,1922—NWCalifornia(WUSA). S.t.mariposaeGrinnell,1913—SCOregon,N&amp;CCalifornia,andWCNevada(WUSA). S. t. montereyensis Merriam, 1895 — W California (W USA). <b>Descriptive notes.</b> Head—body 57-75 mm, tail 50-64 mm, hindfoot 13-16 mm; weight 4-6 g. Trowbridge’s Shrew is relatively small. Dorsum varies considerably between gray, grayish brown, and dark charcoal-gray, and venter is generally about the same color of dorsum but slightly paler and grayer. Pelage is grayer in winter and browner in summer. Feet are whitish; ears are short and barely extend past fur. Tail is ¢.85% of headbody length and sharply bicolored (unlike most other species of Sorex), being dark brown above and lighter below. There are five unicuspids, and teeth are pigmented dark red; third and fifth unicuspids are significantly smaller than first, second, and fourth. Chromosomal complement is rather variable and has 2n = 31-42, FN = 56-60. <b>Habitat.</b> Various habitats with abundant ground litter or vegetation, including dry and moist mature forests, forested canyons and ravines, swampy woods, riparian fringe areas, chaparral (near southern California), and even logged forest with sufficient ground cover at elevations up to 1820 m. On Destruction Island, Washington, USA, Trowbridge’s Shrew is found in deep rank grass near salmonberry (Rubus spectabilis, Rosaceae) thickets. It is often associated with conifer forests dominated by Douglas fir (Pseudotsuga menziesii, Pinaceae). <b>Food and Feeding.</b> Trowbridge’s Shrew feeds on various small invertebrates and seeds, along with other plant material and fungi on occasion. Unlike most other species of shrews, Trowbridge’s Shrews eat large amounts of vegetation and are considered feeding generalists. Their prey generally includes various insects (Neuroptera, Coleoptera, Diptera, Lepidoptera, Hemiptera, and Hymenoptera), arachnids, centipedes, earthworms, snails, and Planaria flatworms. Seeds of conifers are generally eaten, including those from Pseudotsuga, Picea, and Pinus, those from Abies are sometimes eaten but not when the other three are abundant. Trowbridge’s Shrews also eat hypogeous Endogonaceae fungi. In captivity, they have been known to hoard seeds by burying them in a different area; in the wild, this would disperse seeds for the trees. Seeds and other vegetation are fed on more commonly in winter. Non-breeding individuals eat c.1-43 g of food/g of body mass/day, and breeding individuals eat c.0-91 g of food/g of body mass/day. <b>Breeding.</b> Reproduction of Trowbridge’s Shrew tends to occur from late winter until late spring or early summer: March-May in Washington, February until early June in Nevada, and February—June in California. Breeding season is longer in southern parts of the distribution. Litters have 3-6 young, and in warmer areas, sexual maturity is reached at younger ages. Trowbridge’s Shrews only live ¢.18 months. <b>Activity patterns.</b> Trowbridge’s Shrews are active day and night, but they are more active during periods of darkness. They sleep often during 24hours and are active for c.39% of this time. Bursts of activity are generally short and occur about every hour throughout the day and night. Breeding shrews are generally more active but eat significantly less because they spend more time looking for mates. <b>Movements, Home range and Social organization.</b> Trowbridge’s Shrews are solitary when not breeding or rearing young. They burrow more often than many other species of shrews in North America to find hypogeal prey and bury seeds under organic matter or leaf litter. Overall population size in autumn is generally twice that of the population size in spring. <b>Status and Conservation.</b> Classified as Least Concern on The IUCN Red List. Trowbridge’s Shrews are common throughout the relatively wide distribution and do not seem to have any identifiable threats. Logging can either have a positive or negative affect on overall abundance, so they seem to be resilient. They might be locally threatened by domestic cats that are known to kill them but do not eat them, possibly because of their pungent smell. <b>Bibliography.</b> Brown (1974), Carraway (1987), Cassola (2016s), Esteva et al. (2010), George (1989), Ivanitskaya (1994), Jackson (1928), Jameson (1955), Junge &amp; Hoffmann (1981), Rust (1978), Terry (1981).
description: Published as part of <i>Russell A. Mittermeier &amp; Don E. Wilson, 2018, Soricidae, pp. 332-551 in Handbook of the Mammals of the World – Volume 8 Insectivores, Sloths and Colugos, Barcelona :Lynx Edicions</i> on pages 405-406, DOI: 10.5281/zenodo.6870843