Interactions

             Sorex pacificus, eats a variety of different types of food, but it is known as for being an insectivore, which means that it survives by eating insects (Carraway 1985). Commonly eaten insects include earthworms, various beetle species, and flying insects including moths and bees. In addition to insects, it enjoys eating fungi, flower parts, and douglas fir seeds (Carraway 1985). A meticulously in-depth study by John Whitaker and Chris Maser examines the intestines of five western oregon shrews and the exact species of insects that are most commonly ingested by the Pacific shrew, which can be viewed here. 

             As a member of the shrew family, the Pacific shrew has one of the highest metabolic rates of any animal that exists today (Gillihan and Foresman 2013). This species consumes up to three times its body weight in 24 hours (Schmidt 1994) due to the fact that they have a large surface area to volume ratio, which causes them to lose much more heat than other mammals (Merrick 2013). The boreal habitat that these shrews live in necessitate that they eat every three to four hours to avoid starving because much of the energy they acquire is lost as body heat (Schmidt 1994).
            Having a high metabolic rate forces Sorex pacificus to be an efficient hunter and influences its eating behaviors. Although the Pacific shrew has poor eyesight, it has evolved hearing, smell, and touch senses that are sufficient for finding more than enough prey items (Carraway 1985). Echolocation is an additional sense utilized, but appears to mostly be for exploring the environment than for hunting prey (Schmidt 1994). To ensure a continuous supply of food, Sorex pacificus has been observed storing excess food near its nest (Verts and Carraway 1998).
            All of this time spent searching for food unfortunately exposes it to predation from many different organisms. The most common predator of the Pacific shrew is owls, some of which include barn owls, barred owls, great gray owls, and northern pygmy owls, but it is also consumed by large mammals like bobcats. (Gillihan and Foresman 2004). Sorex pacificus is killed by many more predators, but most of them do not consume the shrew due to the foul odor and taste emitted from the glands located on its rear end (Schmidt 1994). In addition to predatory interactions, parasites are common throughout the year for the Pacific shrew. Most of the parasitic infections occur during the summer and include infections by the intestinal fluke, tapeworms, and fleas (Gillihan and Foresman 2004).
            Unlike mice, members of the shrew family are generally considered to be beneficial, or at least not harmful, to humans. It has been noted that due to the voracious appetites of shrews, they can be used to control insect populations in areas where crop damage due to insects is common (Churchfield 1990). Despite this helpful feature, Sorex pacificus will occasionally eat Douglas-fir seeds, which can damage tree crops and forests. In addition, shrews will defend themselves if cornered, even if it means they need to attack pets or even people (Schmidt 1994).

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