Habitat and Geography

      The Pacific shrew, as you may have guessed, is endemic to the Pacific coast of the United States. Having a very specific habitat, it is found along the coast of Oregon and into northern California between 120° and 130° west, and surrounding 42° north (Carraway 1985). The shrew’s habitat stretches inland into Oregon, simply because this land is supportive of its growth and reproductive success. Very few other areas in the world, if any, provide the same resources as this area of the United States for the Pacific shrew to thrive. Sorex pacificus has a very limited geographic distribution compared to most of its close relatives, such as Sorex vagrans, which thrives in parts of Canada, Oregon, Washington, California, Idaho, Nevada, Utah, and Wyoming (Gillihan and Foresman 2013).    Pacific shrew habitat: IUCN Red List of Endangered Species        
     One of the most common locations for studies on the Pacific Shrew is the Jackson State Forest, located along the coast of northern California. Nestled in a protected forest along the coast, this area provides the perfect location for the Pacific shrew to prosper. A damp environment is preferred by the Pacific shrew, which entails a favored niche consisting of decomposing matter on the forest floor, such as logs, stumps, and areas of intense thicket coverage. Locations with these characteristics include coastal, marine areas that do not have extreme elevation changes. In Oregon, the shrew can be found specifically in areas with alder, salmonberry, and skunk cabbage. Contrastingly in California, it is often located in compact redwood or spruce forests (Whitaker and Maser 1975).  In this way, deforestation and forest fires have immense implications on the Pacific shrew. From the year 2000 to 2012, there were a recorded 29 forest fires in California alone. While controlled burns have their environmental benefits, wildfires have irreversible devastating effects on organisms of all types (State of California 2012). However, these effects are magnified on organisms such as the Pacific shrew because it is relies so heavily specifically on the Oregon/Northern California area. When muddy marshes and moist ditches covered in brush or entire forested areas are lost to natural disasters and human interactions, the Pacific shrew loses its habitat and struggles to survive and reproduce. Fortunately for the shrew, its habitat is largely covered by protective areas such as Crater Lake National Park, which holds environmental sustainability to the utmost regard (NatureServe 2008). Jackson State Forest: Jerri-Jo Idarius. Used with permission.
    As previously mentioned, the Pacific shrew prefers ground cover in its habitat. However, when necessary, it will tunnel considerably to avoid predation and find its main source of food: insects. The shrew can also be seen preying upon slugs, salamanders, snakes, snails, and other small invertebrates, and rarely will feed upon seeds and other vegetation (Maser and Hooven 1974). Because the Pacific shrew is a nocturnal mammal, it is unique in that it does not have as much competition during the nighttime finding food because the majority of mammals are daytime hunters. Furthermore, the risk of being preyed upon is greatly reduced simply because the number of active predators is reduced during night hours. To learn more about the Pacific shrew’s interactions with other organisms, visit our interactions page.
    To the Pacific shrew, having a nest is a vital aspect to life. Without a nest, the shrew becomes very uneasy and erratic in its movements (Maser and Hooven 1974). Seemingly, the shrew can sense it is unsafe in the open environment during daytime hours and will immediately burrow into substrate if a nest is not available to provide protection, especially in the presence of a possible predator. More information on the shrew’s unique nesting habits can be found on the form and function page.             

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