North American Jumping Mice (Genus Zapus) Part 6

_Behavior._--Svihla and Svihla (1933:131) write that the long tail of _Z. trinotatus_ is used as a balancing organ when the mouse is in motion. A tailless mouse, attempting to escape, turned somersaults in the air and invariably landed on its back; the loss of its tail seemed to leave the mouse without compensation for the vigorous push of the hind legs. Dalquest (1948:371) noted that the jumping mouse sometimes walks on all fours, but ordinarily moves by means of short hops on the hind feet alone. When startled, jumping mice travel in bounds of six feet or more at a jump.

_Zapus trinotatus_, according to Bailey (1936:232) and Elliot (1899:261), is mainly nocturnal but occasionally is active in daylight.

Svihla and Svihla (_op. cit._:132) heard captive animals make squeaking noises when fighting. On several occasions captive animals made a drumming noise by rapidly beating the tail against a resonant body such as the bottom of a tin can.

Concerning hibernation, Bailey (_loc. cit._) remarks that animals of this species in Oregon, become fat in early autumn and lay down excess adipose tissue under the skin, over the muscles, and in the abdominal cavity. Svihla and Svihla (_op. cit._:133) noted that captives from the Olympic Peninsula, Washington, gained weight in September and October and became extremely fat. With the additional weight they were more listless and drowsy, often spending days curled up in the hibernating position with the head between the hind legs and the long tail curled completely over the head and body. Warmth aroused the animals to activity, but when the temperature dropped they again hibernated.

Flahaut (1939:17) reported the discovery on February 23, 1939, at Henderson Inlet, South Bay, Thurston County, Washington, of two nest cavities inhabited by jumping mice that were hibernating. The nests, four inches apart and 30 inches below the surface of the ground, were approximately five inches in diameter and made of shredded paper. Both mice were dormant, covered by nesting materials and curled up in the aforementioned hibernating posture. Dalquest (1948: 371) writes that in the lowlands of Washington this species disappears by late July but that in the mountains it remains active until the middle of September. Edson (1932:56) records an individual taken on April 20 from its place of hibernation beneath the roots of a decaying stump. This animal quickly roused in the warm mid-afternoon sun but became dormant again when the temperature dropped to 45 F. It seems that animals near the end of hibernation become active on warm days and return to the torpid state on cold ones.

_Enemies._--Little is recorded concerning enemies of _Z. trinotatus_, but Bailey (1936:233) lists owls and other nocturnal birds, weasels, skunks, and badgers as preying on this mouse. Smith and Hopkins (1937:191) found _Z. t. orarius_ in barn owl pellets obtained in Elk Valley, Marin County, California.

_Food._--Bailey (_loc. cit._) remarks that in Oregon, these mice feed mainly on small seeds of gra.s.ses, small grains (wheat, barley, oats, and rye), and other plants. These seeds are obtained by cutting the stems, drawing the stems down and biting off lower sections until the seed-laden heads are reached. Bailey (_op. cit._:234) found that _trinotatus_ utilized also the seeds of the western skunk cabbage.

Near Seattle, Washington, according to Dalquest (_loc. cit._), the princ.i.p.al food of _Z. trinotatus_ was velvet gra.s.s (_Holchus lanatus_), broad-leaved dock, and the seeds of other gra.s.ses. Dalquest reports also that the fruit of the blackberry (_Rubus macropelatus_) is eaten and that an occasional jumping mouse has its chin stained a deep purple by juice from these berries.

_Reproduction._--There is normally a single litter of from four to eight young per year according to Bailey (_loc. cit._). Newly born young have been described by Svihla and Svihla (1933:132) as follows: slightly smaller than newly born harvest mice (_Reithrodontomys m. megalotis_), average weight .8 grams, hairless (without even vibrissae visible), pink, eyes closed, ears folded, heads short and stubby, tails long (longer than those of newly born _Peromyscus_), and bodies surprisingly small (when compared with newly born _Peromyscus maniculatus_).

=Zapus trinotatus eureka= A. B. Howell

_Zapus trinotatus eureka_ A. B. Howell, Univ. California Publ., Zool. 21:229, May 20, 1920.

_Zapus trinotatus trinotatus_, Preble, N. Amer. Fauna, 15:26, August 8, 1899 (part--the part from Crescent City and Carsons Camp, Mad River, California).

_Zapus orarius_ Preble, N. Amer. Fauna, 15:29, August 8, 1899 (part--the part from Eureka and Carsons Camp, Mad River, California).

_Type._--Female, adult, skin and skull, No. 11703, Mus. Vert. Zool.; Fair Oaks, Humboldt County, California; obtained on August 27, 1910, by Joseph S. Dixon, original No. 1743.

_Range._--Northwestern coastal region of California, from Russian Gulch State Park, Mendocino County north to Trinidad, Humboldt County. Zonal range: humid Transition.

_Description._--Size medium; color dull; back near Ochraceous-Buff with heavy admixture of black hairs, forming broad dorsal band; sides from near Ochraceous-Buff to near Ochraceous-Salmon, sometimes with heavy admixture of black hairs; lateral line usually distinct, sometimes blending with color of belly and side; ventral surface usually suffused with color of sides; tail bicolored, dark brown above, white to yellowish-white below; feet grayish-white above; ears dark, edged with color of sides; auditory bullae large; pterygoid fossae broad; incisive foramina relatively short; palatal bridge short; maxillary tooth-rows relatively short; narrow across zygomata; braincase narrow; interorbital region narrow; zygomatic arch relatively short.

_Comparisons._--From _Zapus trinotatus trinotatus_, _Z. t. eureka_ differs in: Size smaller; ventral surface with much greater suffusion of ochraceous; auditory bullae larger; pterygoid fossae relatively broader; frontal region less inflated; palatal bridge shorter; braincase narrower; narrow across zygomata; upper tooth-rows shorter.

For comparison with _Zapus trinotatus orarius_ see account of that subspecies.

_Remarks._--Howell (1920:230), without having examined the material, provisionally referred specimens from Requa and Crescent City, Del Norte County, California, to _Z. t. eureka_. I have studied this material and find the specimens to be intermediate between _Z. t. trinotatus_ and _Z.

t. eureka_ in cranial characters (zygomatic breadth, interorbital width, and breadth of braincase), but nearer _Z. t. trinotatus_ in coloration (absence of ochraceous suffusion ventrally). They are here referred to _Z. t. trinotatus_. The zone of intergradation between _Z. t.

trinotatus_ and _Z. t. eureka_ seems to extend from Requa, California, north to Gold Beach, Oregon, where other specimens intermediate between these two subspecies, have been obtained. These individuals are also referred to _Z. t. trinotatus_ on the basis of cranial features and color.

_Specimens examined._--Total, 42, all from California, distributed as follows: _Humboldt Co._: Trinidad, 4 (SDM); Carsons Camp, Mad River, 3 (USBS); 3 mi. W Arcata, 5 (MVZ); _7-3/10 mi. E Bayside_, 1 (MVZ); _12 mi. S Korbel, on Maple Creek_, 2 (MVZ); _Falk_, 1 (MVZ); Carlotta, 1 (MVZ); _F. B. Summer Redwoods, S Eureka_, 1 (MVZ); _Maple Creek, 1 mi. W junction Mad River_, 12 (MVZ). _Mendocino County_: Mendocino City, 1 (MVZ); Albion River, 1/3 mi. E MacDonalds Ranch, 1 (MVZ); Russian Gulch State Park, 10 (MVZ).

_Marginal records._--California: Trinidad; Russian Gulch State Park; Albion River, 1/3 mi. E MacDonalds Ranch; Mendocino City; Carlotta.

=Zapus trinotatus monta.n.u.s= Merriam

_Zapus trinotatus monta.n.u.s_ Merriam, Proc. Biol. Soc. Washington, 11:104, April 26, 1897; Bailey, N. Amer. Fauna, 55:234, August 29, 1936.

_Zapus monta.n.u.s_, Preble, N. Amer. Fauna, 15:28, August 8, 1899.

_Type._--Female, adult, skin and skull; No. 79863, U. S. Nat. Mus., Biol. Surv. Coll.; Crater Lake, Klamath County, Oregon; obtained on August 19, 1896, by Edward A. Preble, original No. 1388.

_Range._--From Crater Lake, Klamath County, Oregon, northward along the Cascade Range into Hood River County, Oregon. Zonal range: Transition and Canadian.

_Description._--Size medium; back near Ochraceous-Buff with admixture of black hair, resulting in a grizzled, broad, dorsal band; sides lighter than back, from near Ochraceous-Buff to near Pinkish-Cinnamon, and lined with black hair; lateral line distinct; underparts usually pure white, sometimes with slight suffusion of ochraceous on lower throat and upper chest; tail bicolored, brown above and yellowish-white below; ears dark, sometimes flecked with ochraceous, edged with yellowish-white; feet grayish-white above; braincase relatively narrow; zygomata relatively short; condylobasal length short; mastoid region relatively narrow; palatal bridge short; auditory bullae large; frontal region inflated; pterygoid fossae relatively narrow.

_Comparison._--From _Zapus trinotatus trinotatus_, _Z. t. monta.n.u.s_ differs as follows: Size averaging smaller; sides more ochraceous, fewer black hairs; upper parts duller; skull smaller; zygomatic arch shorter, braincase relatively narrower; frontal region more inflated; pterygoid fossae relatively narrower; zygomata narrower.

_Remarks._--The systematic status of _Z. t. monta.n.u.s_ has been in doubt.

Several workers, for example, Howell (1920:227) and Preble (1899:28), considered it to be a species, and others (Merriam, 1897a:104, Bailey, 1936:234) considered it to be a subspecies of _Z. trinotatus_. _Z.

monta.n.u.s_ is here considered to be a subspecies of _Z. trinotatus_, because of the agreement of the two in size and shape of the baculum, diameter and pigment pattern of the hair, and the over-all proportions of the skull. In addition, animals from intermediate geographic areas are available and show actual intergradation.

Intergradation has been noted in specimens from North Santiam River, 3400 ft., Oregon. In color, in length of incisive foramina, in breadth of braincase, and in width of zygomata these specimens are intermediate between _Zapus trinotatus monta.n.u.s_ and _Z. t. trinotatus_, but in the sum-total of characters they are referable to the former. Specimens from Lost Creek R. S., 10 mi. SE McKenzie Bridge, are intermediate in color between _Z. t. trinotatus_ and _Z. t. monta.n.u.s_; they are referable to _Z. t. monta.n.u.s_. The animals available from Brooks Meadow, 4300 ft., 9 mi. ENE Mt. Hood and the one from Mt. Hood, in color, in length of incisive foramina, and in mastoid width, closely approach _Z. t.

trinotatus_ from Skamania County, Washington, but in the sum-total of characters are nearest _Z. t. monta.n.u.s_ and are here referred to _monta.n.u.s_.

_Specimens examined._--Total, 35, all from Oregon, distributed as follows: _Deschutes County_: Tumalo Creek, 15 mi. W Bend, 6100 ft., 3 (MVZ). _Douglas Co._: Diamond Lake, 1 (USBS). _Hood River Co._: Brooks Meadow, 4300 ft., 9 mi. ENE Mt. Hood, 10 (MVZ); _Mt. Hood_, 1 (USBS).

_Klamath Co._: _Crater Lake_, 3 (MVZ); _1/2 mi. N Government Camp, 6700 ft., Munson Valley, Crater Lake Nat'l Park_, 2 (MVZ); east slope Cascade Divide, 6400 ft., Crater Lake Nat'l Park, 2; Anna Creek, Mt. Mazama, 6000 ft., 2 (USBS). _Lane Co._: Lost Creek R. S., 10 mi. SE McKenzie Bridge, 6 (USBS); _Three Sisters, Alder Springs, 4300 ft._, 2 (USBS).

_Linn County_: North Santiam River, 3400 ft., 3 (MVZ).

_Marginal records._--Oregon: Brooks Meadow, 4300 ft., 9 mi. ENE Mt.

Hood; Tumalo Creek, 15 mi. W Bend, 6100 ft.; Anna Creek, Mt. Mazama, 6000 ft.; east slope Cascade Divide, 6400 ft., Crater Lake Nat'l Park; Diamond Lake; North Santiam River, 3400 ft.

=Zapus trinotatus orarius= Preble

_Zapus orarius_ Preble, N. Amer. Fauna, 15:29, August 8, 1899.

_Zapus pacificus_ Merriam, Proc. Biol. Soc. Washington, 11:104, April 26, 1897 (part--the part from Point Reyes, Marin County, California).

_Zapus trinotatus orarius_, Hooper, Miscl. Publ. Mus. Zool. Univ.

Michigan, 59:67, January 12, 1944.

_Type._--Male, adult, skin and skull, No. 250, collection of E. A. and O. Bangs (now in Mus. Comp. Zool.); Point Reyes, Marin County, California; obtained on May 14, 1893, by C. A. Allen, original No. 618.

_Range._--Southern and western Marin County, California. Zonal range: Upper Sonoran areas that are moist yet safe from continuous inundation.

_Description._--Size small; back dark ochraceous, usually overlaid with black hairs forming broad dorsal band; side lighter than back with admixture of black hairs; lateral line distinct, usually bright, near Ochraceous-Buff; under parts strongly suffused with ochraceous; tail bicolored, white to yellowish-white below and dark brown above; feet grayish-white above; ears dark, edged with yellowish-white or tan; skull small; zygomata narrow; braincase narrow; maxillary tooth-rows short; interorbital region narrow; incisive foramina short; palatal bridge relatively long; mastoid region relatively broad; occipitonasal length short.

_Comparison._--From _Zapus trinotatus eureka_, _Z. t. orarius_ differs in: Size smaller; color, dorsally and laterally, brighter, more ochraceous; skull averaging smaller in all measurements taken except length of palatal bridge, where it averages longer; auditory bullae smaller, less inflated; pterygoid fossae narrower.

_Remarks._--Preble (1899:30) named this jumping mouse as a full species.

Included in the specimens examined were animals from Eureka and Mad River, Humboldt County, California. Howell (1920:231) retained _Z.

orarius_ as a full species but restricted its range to Marin County, California, and referred material from northern California, including the animals from Eureka and Mad River, to a new subspecies (_eureka_) of the species _Z. trinotatus_. Howell (_loc. cit._) suggested that _Z.

orarius_ had its closest affinity with _Z. t. eureka_ but remarked that intergrading material was not available. Hooper (1944:68) arranged _Z.

orarius_ as a subspecies of _Z. trinotatus_ and suggested that intergrades could be expected from geographically intermediate areas, for example, northern Sonoma County, California.

Although animals from intermediate geographic areas still are not available to show actual intergradation, I concur with Hooper (_loc.

cit._) and arrange _Z. orarius_ as a subspecies of _Z. trinotatus_. The close relationship of _Z. orarius_ to _Z. trinotatus_ is evident; certain diagnostic characters, held in common, are the shape and size of the os p.e.n.i.s, the diameter and pigment pattern of the hair, and the general configuration of the skull.