{| style="float: right;" |  |- | thumb|distribution of the american water shrew in northern america |- |  |- |  |} == the american water shrew == the âââamerican water shrewâââ (sorex palustris) or northern water shrew, is found in the nearctic faunal region located throughout the mountain ranges of northern united states and in canada and alaska. == physical description == the american water shrew is considered a species that is sexual dimorphic in which the males are in general bigger and heavier than the females. the size of the shrew can be anywhere from 130â170&nbsp;mm and weigh from 8-18 grams. their tails range from 57â89&nbsp;mm. the shrew contains black and brown fur colors and changes depending on the season. the color will change to lighter brown in the summer and a black color in the winter. air bubbles are trapped in the thick fur when the animal dives underwater. the air bubbles help the shrew with buoyancy and also allow it to engage in a behavior called âwater-walkingâ. the water shrew can dive underwater for about 15 seconds, but is only able to if it is swimming vigorously. the air bubbles allow the shrew to swim, but as soon as the shrew stops swimming, then it will shoot back up to the surface.  its feet have a fringe of hairs, more visible on the larger hind feet, which allow this animal to run on the water's surface. == dentition and eating habits == the american water shrew has a larger skull ranging from 21 to 23 mm and width 10 to 11 mm and contains a dental formula of 1/1 5/1 1/1 3/3 with a total of 32 teeth. they swim well and make short dives in search of food. the shrew prefers aquatic insects such as; stone flies an
IUCN_Red_List_least_concern_species Mammals_of_the_United_States Sorex