Part 12

Remarks.--This subspecies retains most of its diagnostic characters throughout nearly all parts of its geographic range. Intergradation occurs between Z. t. eureka and Z. t. trinotatus in extreme southwestern Oregon and northwestern California (see account of Z. t. eureka). Intergrades between Z. t. montanus and Z. t. trinotatus have been commented on in the account of Z. t. montanus. Specimens from Eugene, Oregon, according to Bailey (1936:232), show affinity to Z. t. montanus but are considered by him to be Z. t. trinotatus.

Specimens examined.--Total, 238, distributed as follows:

BRITISH COLUMBIA: Alta Lake, on Pac. Gt. Eastern Ry., 2600 ft., 5 (MVZ); Okanagan, 1 (FM); Vedder Crossing, 4 (1 MVZ, 3 PM); Chilliwack Valley, 2 (NMC); 18 mi. S Chilliwack, 1 (MVZ); Cultus Lake, 2 (NMC); Lihumption Park, 4500-4800 ft., 12 (NMC); Seymour Mtn., 4000 ft., 8 (1 MVZ, 7 PM); Cariboo, 2 (FM); Sumas, 8 (1 MVZ, 7 FM); Huntingdon, 40 (NMC); Parnassus Creek, Black Tusk Meadow, 5200 ft., 1 (PM); Howe Sound, Brackendale, 2 (NMC); Stanley Park, Vancouver, 1 (PM); Allison Pass, Manning Park, 1 (PM); Manning Park, 2 (PM).

CALIFORNIA: Del Norte Co.: Crescent City, 11 (6 FM, 5 USBS); Requa, 4 (FM).

OREGON: Benton County: 3 mi. N Corvallis, 2. Clatsop County: Old Fort Clatsop, 100 ft., 11 (MVZ); 7-1/2 mi. S Cannon Beach, 50 ft., 1 (MVZ). Columbia County: 7 mi. SE Rainier, 100 ft., 11 (MVZ). Curry County: Gold Beach, 3 (FM). Douglas County: Gardiner, 7 (5 MVZ, 2 FM). Lane County: Sutton Lake, 6 mi. N Florence, 1 (MVZ). Lincoln County: Delake, 3 (2 MVZ); Newport, 2 (MVZ). Multnomah County: Portland, Council Crest, 950 ft., 1 (MVZ). Tillamook Co.: Tillamook, 1 (MVZ); 9 mi. S Tillamook, 1 (MVZ); Netarts, 3 (SDM); Blaine, 3 (MVZ). Washington County: 18-1/2 mi. NW Portland, 1300 ft., 5 (MVZ).

WASHINGTON: Clallam County: Deer Lake, 3800 ft., 3. Clarke County: 3-1/2 mi. E and 1-1/2 N Amboy, 3500 ft., 3 (MVZ); 1-1/2 mi. ENE Amboy, 3500 ft., 13 (MVZ); 3-1/2 mi. E and 5 mi. N Yacolt, 500 ft., 1 (MVZ); 1-1/2 mi. W Yacolt, 800 ft., 11 (MVZ). Cowlitz County: 6 mi. NE Kelso, 4 (MVZ); 4 mi. E mouth Kalama River, 5 (MVZ). King County: Lakeridge Tract, S end Forest Ave., Lake Washington, 2 (MVZ); Seattle 2 (MVZ); Snoqualmie Pass, 5 (MVZ). Mason County: Potlatch, 2 (MVZ). Pacific County: 1-1/2 mi. N Chinook, 10 ft., 1 (MVZ); 3-1/2 mi. SE Chinook, 10 ft., 5 (MVZ). Pierce Co.: 5 mi. E Tacoma, 4 (MVZ); Puyallup, 3 (1 MVZ, 2 FM); Mt. Rainier, 1 (MVZ); 3 mi. E Ashford, 1 (LMH). Skamania County: Ice Caves, 2800 ft., 5 mi. WSW Guler, 1 (MVZ). Thurston County: Boston Harbor, 5 (CAS). Wahkiakum County: 4 mi. E Skamokawa, 5 (MVZ). Whatcom County: Baker Lake, 2 (MVZ).

Marginal records.--British Columbia: Okanagan; Manning Park. Washington: Baker Lake; Snoqualmie Pass; Mt. Rainier; Ice Caves, 2800 ft., 5 mi. WSW Gulch. Oregon: Portland, Council Crest, 950 ft. California: Requa; Crescent City. Oregon: Gold Beach; Gardiner; Sutton Lake, 6 mi. N Florence; Newport; Netarts; Old Fort Clatsop, 100 ft. Washington: 3-1/2 mi. SE Chinook, 10 ft.; Deer Lake, 3800 ft. British Columbia: Stanley Park, Vancouver; Alta Lake, 2600 ft.

=Zapus princeps= Allen

(Synonymy under subspecies)

Range.--The Rocky Mountains region from Yukon south into Arizona and New Mexico; westward through eastern Oregon and through the Cascades and Sierra Nevada of California; eastward in the northern Great Plains to extreme eastern parts of the Dakotas (see fig. 46).

Characters of the species: External.--Size medium to large (total length 216 mm to 247 mm); tail longer than head and body (129 mm to 148 mm) and bicolored, pale brown to grayish-brown above, white to yellowish-white below; hind feet long (31 mm to 34 mm), grayish-white above; back variable from yellowish-gray to salmon-brown and ochraceous; sides paler than back; lateral line usually present but sometimes indistinct or entirely absent (when present usually clear Ochraceous-Buff); ventral coloration white, usually suffused with ochraceous; ears usually dark, sometimes flecked and usually narrowly edged with light color; guard hairs average 142 microns (130u to 168u) in diameter; underhair with medullary pigment in form of hollow squares; cuticular scales of underhair larger and fewer than in other species.

Baculum.--Size medium (total length 5.6 mm to 6.6 mm); base moderately broad (0.7 mm to 0.8 mm); tip narrow (0.26 mm to 0.31 mm) rounded and dished out in dorsal aspect, blunted; shaft rounded, slightly sinusoidal, recurved at tip.

Skull.--Large, not exceptionally broad and deep in relation to length; rostrum broad but tapering; pterygoid fossa moderately narrow; anterior ramus of zygomatic process usually broad; incisive foramina usually broadly rounded and elongate; auditory bullae usually moderately inflated; coronoid process of mandible relatively short. Upper premolars of medium size (averaging .55 mm in length and .50 mm in breadth), sometimes functional, with occlusal surface normally divided by single shallow re-entrant fold; m1 relatively short, narrow anteriorly.

Guide to subspecies

1. Z. p. cinereus 7. Z. p. oregonus 2. Z. p. curtatus 8. Z. p. pacificus 3. Z. p. idahoensis 9. Z. p. princeps 4. Z. p. kootenayensis 10. Z. p. saltator 5. Z. p. luteus 11. Z. p. utahensis 6. Z. p. minor]

GEOGRAPHIC VARIATION

There are 11 subspecies recognized, most of which are in the mountains of the western United States and southwestern Canada. There is geographic variation in color, relative proportions of external parts (tail, hind feet, head, and body), and shape and size of the skull.

Three basic types of coloration occur in Z. princeps, as pointed out by Hall (1931:9). Yellow-sided dark-backed jumping mice exemplified by kootenayensis, idahoensis, and utahensis are found to the eastward in the Rocky Mountains. Reddishbrown-sided, brown-backed jumping mice typified by luteus and pacificus are found to the westward in the Sierra Nevada and in New Mexico and Arizona; mice with yellowish-buff or pinkish-buff-sides and light backs are the subspecies, cinereus, curtatus, and oregonus, that occur in the intervening Great Basin.

External dimension as a whole decreases from north to south, although not uniformly. For example, the smallest individuals are of the southernmost geographic subspecies (Z. p. luteus), but the largest are of the subspecies (Z. p. utahensis) that is near the geographic center of the range for the species. In the skull there is geographic variation in the length and shape of the zygomata, size and shape of the incisive foramina, alignment of maxillary tooth-rows, size and shape of auditory bullae, position of the postpalatal notch in relation to M3, and the presence or absence and size of the medial projection on the inferior ramus of the zygomatic process of the maxillary.

NATURAL HISTORY

Habitat.--Zapus princeps occurs most commonly adjacent to streams where grasses and herbs are in lush growth. It frequents mountain meadows neighboring small streams and is often taken from alder, aspen, or stands of willow, where the moist ground supports a heavy undergrowth of herbs. Davis (1939:330) found these mice in heavy herbage along a small stream bordered by quaking aspen near Victor, Teton County, Idaho. They were found along streams bordered by willow, rose, alder, huckleberry, sedges, and herbs of various kinds at Alturas Lake, Mill Creek, and at the head of the Pahsimeroi River. Linsdale (1938:195) found jumping mice in the Toyabe Mountains, Nevada, near the streamsides or in seepy areas close to the streams where associated vegetation included rose, willow, wild peach, sage, grasses, and herbs. In the Uinta Mountains, Utah, R. D. Svihla (1931:264) obtained them from willows along streams in mountain parks. Borell and Ellis (1934:37) in the Ruby Mountains, Nevada, found jumping mice to be common in heavy vegetation along streams. Louise Kellogg (1916:369) obtained jumping mice in northern California; all were near water, in grassy meadows, or under alders where vegetation was dense.

Zapus princeps is locally abundant, but its numbers seem to vary considerably from year to year as well as seasonally. Early autumn, when young of the year are abroad, seems to be the period of greatest abundance. Moore (1928:154) remarks that runways were plainly marked and well strewn with four-inch pieces of brome-grass. Davis (1939:334) notes that Z. princeps has runways, and found that sections, four inches long, of cut grass piled in runways was good evidence of the presence of the mouse.

Behavior.--In reference to locomotion of Z. princeps, Davis (loc. cit.) writes, "In rapid progression jumping mice move by a series of zigzag hops. One young of the year found in tall grass near Victor made horizontal leaps of approximately three feet. The zigzag course was difficult for me to follow, and I was led to wonder if this mode of locomotion were not advantageous to the mice in eluding animals that would do them harm." Hollister (1912:26) remarked that princeps, when startled, sometimes jumps five to six feet at a bound. Concerning the swimming ability of Z. princeps, Bailey (1936:233) quotes from Hollister's notes, "While I was walking around the grassy border of a small pond one jumped out at my feet and struck in the water like a frog, which at first it was thought to be, until it was seen swimming across the pond on the surface of the water ... he certainly handled himself as if perfectly at home and swam with little effort and great speed over the still surface of the pond." Davis (1939:334) obtained two individuals at Mill Creek, Idaho, in traps placed on artificial islands of stones in the middle of the creek where the water was about six inches deep. He speculated that the only way the mice could have reached the traps was by swimming. Grinnell, Dixon, and Linsdale (1930:531) record an individual which was seen hopping in the inch-deep water of a small stream at Lake Helen, California.

According to Hollister (1912:26) and Davis (1939:335), jumping mice are for the most part nocturnal, but occasionally they are seen by day in tall grass.

Little is recorded concerning the hibernation of Z. princeps. What data are available suggest that, starting in July, these animals accumulate a heavy layer of fat on the inside of the skin with especially large amounts in the inguinal region. By August or early September, animals are excessively fat, and the start of hibernation is dependent then upon the arrival of a heavy cold snap. Grinnell, Dixon, and Linsdale (1930:531), in their study of the vertebrates of the Lassen Peak region of California noted that the latest activity by these mice was September 13. As regards the time of onset of hibernation in Idaho, Davis (1939:336) states that, "I know of no records of capture later than September and infer that hibernation begins in that month or the next." Bailey (1932:227) writes that in New Mexico, animals obtained on September 20 were very fat, probably were ready to hibernate at the first cold wave, and had winter nests in burrows well underground.

Enemies.--Bailey (loc. cit.) lists hawks, owls, and weasels as natural predators on Z. princeps. Stanford (1931:362) records the garter snake (Thamnophis) as a predator of jumping mice. A large snake of this genus obtained by him regurgitated two jumping mice a few hours after its capture. Grinnell, Dixon, and Linsdale (1937:232) report that on Parker Creek, in California, H. C. Bryant frightened a weasel that dropped a freshly killed jumping mouse. Crowe (1943:407) reported Cuterebra fly larvae in the inguinal region of a Z. princeps obtained at Invermere, British Columbia. Several mice of this species taken at Moccasin Lake, 19 mi. W and 4 mi. N of Lander, 10,000 ft., Fremont County, Wyoming, were heavily infested with mites of the family Laelaptidae.

Food.--In early September in central Utah, Moore (1928:154) found only a white, starchy, glutinous paste in stomachs of six Z. princeps and only traces of a brown seed coat in a seventh. The main seeds eaten seemed to be from an introduced brome-grass which was abundant in the vicinity of capture. Bailey (1932:226) wrote of Z. princeps in New Mexico, that "In feeding they cut down the tall grass, beginning at the bottom and cutting the stem at intervals as high as they can reach until the seed part of the grass is brought down." He (op. cit.:227) remarked that the food was almost entirely seeds of grass and grasslike plants and that the stomach contents almost always were perfectly clean white dough from the shelled kernels of small seeds.

Reproduction.--Females with embryos have been collected from late May to mid-July and lactating individuals until late August. Possibly there is only one litter per season as Davis (1939:336) suggests is the case in Idaho.