OCTOBER 1989 - City of Boulder

LEAST SHREW
Distribution. -The least shrew generally occurs in the eastern half
of the United States and is common in Mexico and Central America. In
Colorado, the species is found in the drairiages of the South Platte and
and Republican rivers. There is evidence that the habitat created by
extensive irrigation has allowed the animal to extend its range westward
in the last two decades. In Boulder County the species occurs in wet-
lands to the base of the foothills; it was first traced here in 1966,
near Boulder Reservoir.
Description. -The least shrew is small, with inconspicuous ears,
minute black eyes, and a long pointed snout. Brownish gray in color, the
pelage is fine, dense, short and almost velvety. Its extremely short
tail is less than one-third the total body length, and that distinguishes
it from other shrews.
Measurements of a male and a female from Yuma County were: total
length, 81, 85; tail, 18, 18; hindfoot, 11, 11; weight 5.2, 4.7 gr;
condylobasal length, 15.5, 15.2 ; cranial breadth, 7.7, 7.9.
Natural History.--In the northern part of its range, the least shrew
Inhabits grassy, veedy and brushy fields. It is often associated with
dense herbaceous cover. Burrows may be of several forms but are generally
simple, small, and terminate in a nest. Nests are also found on the sur-
face under logs or human artifacts. Approximately 100 an. -in diameter,
the nests are usually constructed of dried grasses and/or leaves. The
species may be colonial or at least social. This is unusual behavior for
a shrew. Large numbers of the animal often are found together in the
same nest. The species is active at all hours of the day but is most
active at night. The least shrew is active throughout the year.
Food consists almost entirely of insectqearthwor~s, and spiders.
Food habits in Colorado have not been studied, but in Indiana, the larva
of moth beetles, earthworms, spiders and the internal organs of crickets
and grasshoppers made up the bulk of the animal's diet.
Females give birth to litters of three to seven young from March to
November in the northern part of the range. The young are altricial but
development is fairly rapid. Adult weight is reached in about 30 days.
Owls are known to prey heavily on the least shrew. Other predators
include hawks, skunks and falcons. Very little is actually known about
this species. Thorough studies of the animal's population ecology,
genetics, and social behavior remain to be done.
Selected References.-Whitaker (1974); Williams and McArthur (1972).