OCTOBER 1989 - City of Boulder

DEER MOUSE
Peromyscus maniculatus
Distribution- The deer mouse ranges across most of North
America. In Colorado, the species occurs statevide. This is doubtless
the most abundant mammalian species in the Boulder ountain arks.
In live trapping studies, it was taken at all localities.
Description-Medium in size, short ears and short tail distinguish
the deer mouse from the rock mouse. Smooth incisors and larger size
distinguish it from the hamest mice. The animals are brownish to
reddish above and white below, including their feet.
Average (and extreme) external measurements of eleven males from
Larimer County were: total length, U2.9 (142-161); length of tail,
64.5 (58-78); length of hindfoot, 19.8 (18-21); length of ear, 17.3
(15-19 The weights range from 19 to 24 gr. for a full grown adult.
Greatest length of skull ranges from-24.9 to 25.9, .and zygomatic breadth
is 12.7 to 13.7.
Natural History-Deer mice range from above timberline down to
the lowest elevations. They live in all types of topographic settings,
from plains to rocky, broken surroundings. Vegetation may range from
virtually none, to grass, to brush, to woodland. The animals are not
active burrowers. They do remodel small burr- of other species by
accumulating dirt under the body and then depositing it in front of the
hole. Materials such as feathers, hair, plants, and dry grass may be
accumulated to form comfortable living quarters. These -1s tend to
be most active at night.
Food consists of seeds, insects, and fungi. Food habits seem
to shift through the season.
Average nlrmber of litters per year is about 3.5. Litter size was
determined to be about 5.7 (range 2-10, n=4) in Coloradan subalpine
forest. The breeding season is initiated during or after snowmelt
and lasts for 5.5 months. Young deer mice may associate with their
mothers past the age of weaning.
P-mniculatus has many natural predators. There are many birds
of Frey (owls, shrikes, hawks) that make these mice a part of their
diet. Mammalian and reptilian predators also feed on them.
Probably, deer mice are the most important prey base for the mler
carnivores of the Mountain Parks.
Selected References-Halfpenny (1980); King (1968); Merritt and
Merritt (1980); and Stinson (1977).
H.S.T.