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.
[8] The fur colorings change over the year, with a darker more brownish coat in the summer and a lighter gray in winter.
The tail is bi-colored: darker on the top than the bottom, with a sharp line separating the colors.
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.
[11] Fossilized remains of Trowbridge's shrew have been obtained from the Carpinteria Tar Pits.
In the west, the population continues south through the coast range to Santa Barbara County.
[1] Trowbridge's shrew resides in forested areas where the ground may be littered with debris for cover.
Populations on Destruction Island off the Washington coast live in deep rank grass near salmonberry patches.
[8] Known parasites include a number of ticks, mites, chiggers, fleas, worms, and single-celled organisms.
[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.
[12] As they reach sexual maturity, Trowbridge shrews gain whole body mass.
[7] In northern areas, the number of embryos found in pregnant females was fewer and the breeding season appears to be shorter.
The rationale for the listing includes an overall stable population, lack of major threats, and a widespread geographic distribution.