Predatory snakes, birds, and mammals doubtless kill and eat deer mice. Strangely enough, although deer mice may be the commonest mammal in an area, the pellets of owls collected in the same area usually contain the remains of relatively few deer mice. The impact of owls seems to be greatest upon mice, such as Microtus, which follow definite runways.
The breeding season of the deer mouse extends over most of the spring and summer. Growth and development of the young of Peromyscus m. oreas have been discussed by A. [Svihla] (1936A). Embryos found varied in number from 2 to 8 with a mean of 4.5.
Peromyscus maniculatus oreas Bangs
Peromyscus oreas Bangs, Proc. Biol. Soc. Washington, 12:84, March 24, 1898.
Peromyscus akeleyi [Elliot], Field Columb. Mus. Publ. 30., zoöl. ser., 1:226. February 1, 1899 (type from Elwha River, Olympic Mountains, Washington).
Peromyscus maniculatus oreas [Osgood], N. Amer. Fauna, 28:51, April 17, 1909.
Type.—Obtained on Church Mountain, 6,500 ft., Mt. Baker Range, near the U. S. boundary, British Columbia, by Allan Brooks on August 29, 1896; type in Museum of Comparative Zoölogy.
Racial characters.—Size large; tail more than 50 per cent of total length; color of upper parts reddish.
Measurements.—Twenty-five males and 15 females average: total length 202; length of tail 110; hind foot 22.6; ear 18.7.
Distribution.—From the Cascade Mountains west to the Pacific Ocean, save for the Puget Sound area and a narrow band extending southward nearly to the Columbia River. Marginal localities along the west side of Puget Sound are: Deer Park (W.W.D.), Lake Cushman (W.W.D.), and Kelso (M.V.Z.). Marginal localities on the west side of the Cascade Mountains are: Tomyhoi Lake (W.W.D.), Forks of Skykomish River (W.W.D.), North Bend (W.W.D.), Mt. St. Helens (V.B.S.) and Yacolt (M.V.Z.). Marginal localities on the east slope of the Cascade Mountains are: Grouse Creek (W.W.D.), Lake Wenatchee (W.W.D.), Easton (W.W.D.), Morrison Springs Ranger Station (W.W.D.) and Wind River C.C.C. Camp (W.W.D.).