In a long-term study done in Alaska, Yom-Tov and colleagues (2005) found that the masked shrew's body size contradicts Bergmann's Rule.

Results yielded that the masked shrew's body size decreased with high latitudes and with lower mean January temperatures, a trend that opposed Bergmann's Rule.

It was suggested that this may be a coping mechanism to limit total energy requirements due to decreased food availability in winter months.

Additionally, it was shown that body and tail length increased with rising temperatures during the second half of the twentieth century.

[5] Its range covers most of northern North America extending south as far down to Maryland, along the Rocky Mountains in the west, and to the Appalachians in the east.

Predators include larger shrews, hawks, owls, shrikes, snakes, herons, foxes, leopard frogs, bluebirds, brown trout, and weasels.

[6] Cowan and colleagues (2007) found that the high volume of food masked shrews consume causes them to be more susceptible to parasitism.

[5] Masked shrews living at high latitudes are born in late spring and summer, reach adult size by the time they leave their nests, and complete their life cycle within a year.

Masked shrews have a high chance of mortality during their first two months of life and most die during the first year.