Form and Function

      Sorex pacificus, being a creature primarily active at nighttime, has adapted a dark-colored coat to avoid predation during its active hours from sunset to sunrise.  Another adaptation that the shrew has made is its unique hunting abilities. Due to lack of light, the Pacific shrew preys  based on smell and sound alone. The shrew is able to trail insects entirely based on smell as they crawl across the substrate, carefully listening for noises the prey may make in an attempt to flee. If the insect burrows into the soil, the shrew has no problem quickly pursuing the insect and eventually attacking it. Sorex pacificus does not prefer to burrow unless attacking or hiding from predators in circumstances in which other protection is unavailable. It has been observed constantly twitching its nose and making twitching noises during hunting hours, possibly in an attempt to smell or locate prey more efficiently. When insects are flying, the Pacific shrew has been observed attacking mid-air using its acute sense of hearing. However, it is much more likely to wait until the prey has landed and pounce on the insect’s wings (Maser and Hooven 1974). Because of the shrew’s nocturnal habits, its vision is weak at best and is not relied upon except in nest building.                
    The nests built by the Pacific shrew utilize a wide array of materials from its surrounding habitat. This includes small substrate such as decaying mosses, leaves, and minute pieces of wood, which are carried in its mouth to the nesting area (Maser and Hooven 1974). In this way, the structure of the mouth is vital for not only ingestion of insects and small invertebrates, but also for fundamental activities such as shelter building and grooming.                
    Sorex pacificus appears to be a very neat mammal, as it is observed to designate a specific area surrounding its nest for relieving itself (Maser and Hooven 1974). Rather than simply defecating in random areas around the environment, it can be seen having a specific location set aside for these actions. Another characteristic of the Pacific shrew that points towards it being a cleanly creature is its grooming habits. It can be seen grooming multiple times a day, taking up to two minutes per grooming session. A very ornate grooming takes place before laying down to sleep, cleaning every part of the body from the head to the tip of the tail, utilizing both the hind feet to scratch and the mouth to lick clean. When it is time to lay down and rest, the shrew will re-organize its nest before sleeping by pushing and pulling elements of the nest with its mouth and nose. It sleeps with its head curled underneath its body, pointing towards its anus and tail tucked underneath the entire body, and does not seem to sleep laying on its side. This rather peculiar sleeping arrangement could be made in an attempt to conserve body heat. By sleeping in this position, the shrew also is able to awaken and move extremely rapidly if disturbed in its sleep, possibly to escape prey (Maser and Hooven 1974).                
    A final adaptation that sets the Pacific shrew apart from its shrew cousins is what happens after its prey is captured. Not only does it have the incredible ability to seek, find, and attack prey based entirely off sight and smell, but after the prey is attacked, it is not always eaten! While a majority of prey is eaten immediately after being killed, this shrew has adapted the ability to instead carry and store some prey in its nest after being attacked. Because the Pacific shrew is so unique in that it is a nocturnal shrew, it also has acquired this unique adaptation that makes it possible for the shrew to wake up sparingly during the day and snack on the food it has already stored in its nest if desired (Maser and Hooven 1974). 
     To see some of the above behaviors in action, watch this incredible video by the BBC about a close relative to the Pacific shrew, the Northern Short-Tailed shrew.
     To learn more about the Pacific shrew's unique, sometimes erratic behaviors, read this study performed on a captive Pacific shrew. This study also goes into the reproduction and life history of Sorex pacificus, which can be explored further on the next page.

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