Masked Shrew (Sorex cinereus) lives in northern forests across North America. It feeds on insects and seeds. Its conservation status is Least Concern.
Fascinating facts about the Masked Shrew
- Its body shrinks in colder, high-latitude regions, defying Bergmann's rule. A long-term Alaskan study examined 650 specimens collected between 1950 and 2003 and linked size to ambient temperature. The shrew's body length and weight fell as latitude increased and mean January temperatures dropped, a pattern opposite to the rule.
- It can eat about three times its own weight each day, a necessity driven by its extremely high metabolism. Because it must feed almost constantly, the shrew can survive only a few hours without food before energy stores run out. When it rests, its metabolic rate drops, but the need for frequent meals persists throughout day and night. This relentless feeding pattern underpins its ability to sustain rapid growth and activity.
- Without food it can last only a few hours, forcing the masked shrew to forage continuously. It remains active both day and night all year, switching between nocturnal and diurnal habits depending on weather conditions such as rain or cloud cover. This constant activity is supported by its use of tunnels and dry-grass nests, and its home range averages about 0.55 hectare where it must locate prey.
- From summer to winter its body mass drops by half, and it relies on non-shivering heat production to conserve energy during the cold. An adult masked shrew weighs only about 5 g, so the seasonal loss reduces its weight to roughly 2.5 g when temperatures fall.
- Newborn shrews are born hairless, clawless, and with translucent abdominal walls, and they gain weight rapidly, peaking at about twenty days before losing mass as they leave the nest around twenty-seven days. Females produce a single litter of six to seven young each breeding season, which runs from May to September.
Sources
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At a glance
RangeNorth America
HabitatNorthern forests
DietInsects and seeds
About the Masked Shrew
In the secret realm of the underbrush, the masked shrew darts and weaves with an unbridled ferocity, its tiny heart pounding out a staccato rhythm as it pursues its insect prey with relentless abandon. With each fleeting glimpse, the shrew's masked face seems to blur and disappear, only to reemerge in a flash of brown fur as it navigates the dense thicket with an uncanny agility. As it forages, the shrew's very existence is a testament to the enduring power of life in even the most diminutive of packages.
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