Part 21

Sheldon (1934:297) cites a letter from Vernon Bailey in which he remarks on the necessity of abundant moisture and saturate air for hibernating jumping mice. Bailey writes "... they will awaken at times famished for water and will drink and drink before going back to sleep."

Hamilton (1935:195) thinks that in the Ithaca area of New York these mice probably leave their winter quarters in the second half of April and that in southern New York and Long Island they emerge considerably earlier. Quimby (1951:82) and Bernard Bailey (1929:163) report that males appear earlier in the spring than do the females. Quimby (loc. cit.), by recording the sequence and dates of phenological events and appearance of Zapus in several years, was able to predict fairly accurately the time of emergence of Zapus in a succeeding year. In Minnesota, jumping mice emerged late compared to other hibernating rodents.

Enemies.--V. Bailey (1927:119) reports that A. K. Fisher found 50 skulls of Zapus in barn owl pellets taken from the towers of the Smithsonian Institution, Washington, D. C. Dearborn (1932:32) reported mink as having fed on jumping mice. Surface (1906:197) records taking a Zapus from the stomach of a rattlesnake. Pearson and Pearson (1947:138) found remains of Z. hudsonius in pellets of barn owls. Quimby (1951:74) reports two cases of predation on Z. hudsonius; one was by a northern pike, Esox lucius Linnaeus and the other was by a weasel, Mustela sp. Vergeer (1948:91) collected a green frog, Rana clamitans Latreille, which had eaten a jumping mouse.

Quimby (1951:74) frequently found the fleas, Megabothris quirini Rothschild, and Megabothris wagneri (Baker), and occasionally a larval tick, Dermocenter variabilis (Say), on Z. hudsonius. Sheldon (1934:296) remarks that captive animals are burdened with numerous fleas. Hamilton (1935:191) removed a louse from a jumping mouse. One mouse had a hole in the throat and three others had holes in the inguinal region; presumably bot-flies had emerged from these holes. Test (1943:507) found a single Cuterebra larva in the inguinal region of a Z. hudsonius, and Sheldon (1938:328) found Z. hudsonius infested by larvae of Cuterebra fontinella Clark. Here, as in other cases, these larvae were found immediately below the skin. Erickson (1938:252) examined 18 Z. hudsonius obtained in Minnesota, and found that three were parasitized. He found a bot-fly larva, Cuterebra sp., nematodes of the genera Subulura and Spirocerca, and a fluke of the genus Notocotylus.

Food.--Quimby (1951:85-86) studied the food preferences, by presenting to caged Z. hudsonius the plants and invertebrate animals normally available to these mice in nature, and indicates that in general, the starchy fruits of the Gramineae and the less fleshy fruits of various groups of plants are more heavily utilized than other plant materials. His observations indicate that these rodents are highly insectivorous and that they consume many insects under natural conditions. Goodwin (1935:148) reports that the stomach contents of several individuals obtained at South Woodstock, Connecticut, consisted exclusively of blackberries, and that others had subsisted principally on cranberries. Hamilton (1935:197) remarks that seeds are the favored food but that berries, nuts, fruits of various kinds, roots, and insects are also utilized. Stoner (1918:123) writes that the food in cultivated areas of Iowa is various grains as well as grass and weed seeds; in wooded places the mice feed on seeds and nuts of trees. Vernon Bailey (1927:118) states that the examination of a great many stomachs of these jumping mice [in North Dakota] revealed nothing "but the fine white pulp of carefully shelled, well-masticated seeds. Generally these are from grasses, although grain and a variety of other plant seeds are eaten." Schmidt (1931:116) examined the stomach contents of several Z. hudsonius taken in Clark County, Wisconsin, and in most stomachs found the remains of finely chewed roots; however, two from Hewett had eaten several geometrid caterpillars.

Lyon (1938:279), Stoner (1918:123), and J. W. Bailey (1946:263) present information which indicates that Z. hudsonius stores food in its nests or burrows. Possibly these mice awaken at intervals from hibernation and eat.

"These rodents characteristically seize the material to be eaten with the front feet and devour it while reclining on their haunches. The following observation of a caged animal is typical of their feeding habits. The mouse selected a head of yellow foxtail, Setaria glauca (Weig.) Stuntz, from several in the cage, separated it by gnawing through the supporting stem, seized it with the front feet, held it up to the mouth and began to gnaw at one end, stripping all parts from the rachis. The grass head was slowly rotated and shifted sideways until nothing remained but the rachis which was discarded. Actually the seeds were the only parts eaten ..." (Quimby, 1951:73). Sheldon (1934:294) remarks that Z. hudsonius eats from a squatting position and holds the piece of food in the forepaws. The mouse seems to bite off a seed, and then, holding it in the forepaws, transfers it to the mouth.

According to Sheldon (op. cit.:295) and Quimby (loc. cit.), caged jumping mice drink water. When drinking, the mouths of the mice are in contact with the water, but neither observer determined whether the mice lapped or sucked the water. Sheldon (loc. cit.) observed these mice passing stems of long grass through their mouths as though to squeeze out moisture, and thought that the mice obtain most of their required moisture from green plants.

Reproduction.--The breeding season begins shortly after the jumping mice emerge from hibernation in the spring, and reproduction continues until a few weeks before they hibernate in the autumn. The extent of the breeding period probably varies geographically and possibly seasonally. For example, Quimby's (op. cit.:70) information suggests that the 1947 period of parturition occurred between June 15 and August 30 in the area of Centerville, Minnesota. In Michigan, Blair (1940:246) found a peak of breeding activity in spring and another in late summer with little activity in the intervening midsummer. Brimley (1923:263) records a female in North Carolina, with eight embryos on June 13, 1895, and another with seven embryos on September 17, 1891, indicating a strong possibility of two litters per year there. Vernon Bailey (1927:118) records young born in May or June in North Dakota and thinks that there is time for only one litter per year. Petrides (1948:76) captured a female on September 22, 1944, at Athens, Georgia, that gave birth to six young on September 29. This late parturition date indicates a longer breeding season in the southeastern part of the range of Z. hudsonius.

The gestation period of nonlactating, caged Z. hudsonius, Quimby (1951:63) thinks, "is approximately 18 days ... gestation is prolonged in lactating females."

Data from museum labels indicate that embryos in 62 pregnant females averaged 5.4 (2-8) per female. Quimby (1951:67) found the average number of embryos per female for 14 females taken in Minnesota, to be 5.3 and that litters of young found in nests averaged 5.8. Sheldon (1938:330) reports two litters of seven young each and one of four young for Z. hudsonius in Vermont. Petrides (1948:76) records a litter of six young for Z. hudsonius in Georgia. Brimley (1923:263) records one lot of seven and one lot of eight embryos for Z. hudsonius in North Carolina. Vernon Bailey (1923:120) reports six embryos for a female of Z. hudsonius taken in Washington, D. C. Ivor (1934:8) obtained a litter of five young Z. hudsonius from Erindale, Peel County, Ontario. Hamilton (1935:195) records litters of two, four, and five young and embryo counts of four, two, four, and four for Z. hudsonius in New York.

There seems to be two litters per year. According to Quimby (1951:69), "most adult females breed soon after emergence from hibernation and produce the first litters within a month. The remaining females do not breed immediately but produce the first litter," he says, "in the second month after emergence." Both early-breeding females and late-breeding females produce at least 2 litters per year. Those that breed early may have 3 litters.

The appearance and development of growing young of Z. hudsonius in successive weeks is described by Quimby (1951:65). Newborn young are pink and hairless except for microscopic vibrissae. The eyes and external auditory meatus are closed, and the pinnae are folded. The toes are fleshy and clawless; the tail is short in relation to the length of the body. The average weight was .78 grams. The average measurements of three from different litters are: total length, 34 mm; tail, 9.2 mm; hind foot, 4.7 mm. The young are helpless but capable of emitting a high pitched squeaking sound which is audible for several feet.

In the first week of growth the vibrissae become visible to the naked eye, the body changes to flesh color, the dorsal parts become dark gray, the pinna unfolds and is black tipped, and the claws appear. The young now are able to crawl and make a suckling noise, but they are not yet able to support themselves on their legs.

In the second week of development, tawny yellow hair appears on the back and spreads onto the sides. Sparse hair of a lighter color appears on the belly, backs of the feet, and outer surfaces of the legs. Vibrissae are now prominent. The eyes are still closed, but a crack down the center of each is visible by the 13th day. Claws have grown, the longest measuring 1.5 mm. The incisors erupt on approximately the 13th day, those in the lower jaw appearing slightly before those in the upper jaw, and all are white. Activity is increased; nevertheless the young still crawl, make suckling notes, and squeak.

In the third week of development the mice are covered with hair; darker hair appears dorsally; and vibrissae continue rapid growth. The external auditory meatus begins to open on about the 19th day and young react to sound on the 20th. The incisors now are 1 mm long and the claws 1.5 mm long. Young are able to support themselves on their legs, walk, and make one inch hops.

In the fourth week the juvenal pelage is replaced by adult pelage. The eyes open between the 22nd and 25th days. The color of the incisors changes from white to yellowish-orange as in the adults. P^4, M^1, M^2, m1 and m2 have emerged from the maxillary and dentary bones; M^3 and m3 have not yet erupted. A mouse 33 days old had all teeth well developed. By the end of the 4th week the young, except for size, are adultlike and capable of independent existence.

The greatest increase in dimensions of the body is in the first four weeks. A slowing down of growth is simultaneous with weaning.

Other workers, Sheldon (1938:330), Petrides (1948:76), and Ivor (1934:8) also describe the appearance of the young.

Summer nesting sites are usually on the surface of the ground. Jumping mice characteristically construct a globular nest of grass but will utilize other vegetation if grasses are not available. Nests are usually concealed under rocks, logs, bushes, or grass and can be entered by a hole at one side.

Sheldon (1938:328) described a nest of Z. hudsonius found on the ground near the edge of a small hay field. The nest was globular, not more than four inches in outside diameter and two inches in inside diameter; it was closely woven of fine, dry grass and bits of moss. Another nest found in the same field measured 11.5 inches in circumference at the base and six inches in circumference over the top. The inside width and length each was three inches, and the inside height was 3.5 inches. Vernon Bailey (1927:118) remarks that summer nests are placed on the surface of the ground well concealed under grass or other vegetation. He describes the nest as "neat little balls of fine grass with a tiny opening at one side and a soft lining in the central chamber." Cory (1912:249) reports that summer nests are concealed behind rocks or under bushes and thick grass. The nests are round and four or five inches in diameter with an entrance hole at one side. Goodwin (1935:148) examined a nest made entirely of straight, narrow leaves of grass. Ivor (1934:8) found one made of finely shredded jute sacking. Quimby (1951:80) describes several nests: one in the center of a rotten willow log was lined with small pieces of pulpy wood; another was in the rotted wood and debris, at ground level, inside a large, red oak (this globular nest composed of grasses, plant fibers, and rootlets measured six inches in diameter). Another nest was composed of a pile of wood pulp, leaves of oaks, and grasses; this nest was in a hollow root detached from a willow tree.

The mean home range of males, of Z. hudsonius in Minnesota, according to Quimby (1951:86), was 2.70 plus or minus .50 acres; this was significantly larger than the mean home range of females, 1.57 plus or minus .27 acres. According to Quimby (loc. cit.), the size and shape of the home range is influenced by the general features of the terrain, density and type of cover, and land use in the immediate area. Quimby (1951:94) remarked that the home range of the jumping mouse is relatively unstable and Blair (1940:247) stated that the home ranges of both sexes generally overlapped the ranges of other members of the same species and sex. The average size of the home range for Z. hudsonius in Michigan was .89 plus or minus .11 acres for males and .92 plus or minus .11 acres for females.

=Zapus hudsonius acadicus= (Dawson)

Meriones acadicus Dawson, Edinburgh New Philos. Jour., new ser., 3:2, 1856.

Meriones labradorius, Dawson, Edinburgh New Philos. Jour., new ser., 3:2, 1856.

Jaculus hudsonius, Baird, Rept. Expl. and Surv...., 8 (pt. 1):433, July 14, 1858 (part--the part from Nova Scotia, Vermont, and New York).

Zapus hudsonius, Coues, Bull. U. S. Geol. and Geog. surv. of the territories, 2nd ser., No. 5:260, 1877 (part--the part from Nova Scotia, Vermont, and New York); Preble, N. Amer. Fauna, 15:17, August 8, 1899 (part--the part from New Brunswick, Nova Scotia, Maine, New Hampshire, Vermont, Massachusetts, and northeastern New York).

Zapus hudsonius canadensis, Batchelder, Proc. New England Zool. Club, 1:5, February 8, 1899 (part--the part from Keene Valley in Essex County of New York, and Orivell in Vermont); Anderson, Ann. Rept. Provancher Soc. Nat. Hist., Quebec, 1941:35-37, July 14, 1942 (part--the part from the tip of the Gaspé Peninsula in Quebec, New Brunswick, Maine, New Hampshire, Vermont, and New York).