Onychomys leucogaster (Northern Grasshopper Mouse) 

Written by Christa Griffin (Mammalogy Lab--Fall 2003)

Edited by Karah Gallagher and Jennifer Bailey

 The range of Onychomys leucogaster extends all the way from Saskatchewan, Alberta, and Manitoba, Canada through the United States to northern Mexico (McCarty 1978).  In Texas, Onychomys leucogaster is found throughout most of the western part of the state, with the exception of the central part of the Trans-Pecos (Davis and Schmidly 1994).  Its distribution also reaches the Rio Grande Plains of South Texas (Davis and Schmidly 1994).

Physical Characteristics:

Onychomys leucogaster is a stout-bodied mouse with a short, thick tail (Davis and Schmidly 1994).  They are generally grayish buff in color on the upper parts and white the on muzzle, cheeks, forearms and forefeet, and hindfeet under a sharp line of demarcation (Goldman 1939).  The ears are blackish with silvery white margins (Goldman 1939).  In adults there are two color phases, pale and dark (Egoscue 1963).  Instead of light grayish buff, the dark phase is characterized by blackish-brown upper parts with the head and fur around eyes almost black (Egoscue 1963).  At birth, they are pink and hairless except for vibrissae (Svihla 1936).  Juveniles older than 12 days have soft gray pelage the on upper parts and white on the under parts (Svihla 1936).  Juveniles molt into adult pelage 60 to 80 days after birth (Horner 1968; Ruffer 1965a).  The average total length of adults is 164 mm, and the average weight ranges from 27 to 46 grams, sometimes as much as 52 grams (Davis and Schmidly 1994)

Natural History:

Food Habits: Onychomys leucogaster is a carnivorous and insectivorous mouse with nocturnal predatory habits (Pinter 1970; Jahoda 1973).  Eighty-seven percent of their diet is composed of arthropods, mostly the arthropods which feed on plants (Hansen 1975).  Their primary food item in season is the grasshopper as their name implys (Davis and Schmidly 1994).  In addition, they eat a wide variety of insects and insect larvae, spiders, scorpions, other mice, lizards, and seeds (Davis and Schmidly 1994; Flake 1973).  Plant material has also been found to occur in the stomachs of Onychomys leucogaster, but most likely it is from material contained in the guts of the arthropods consumed by the mouse (Hansen 1975).  It seems as though their eating habits change with availability of many arthropods (Flake 1973).  They depend more on seeds and vertebrates for food from mid-autumn through mid-winter most likely because there is a decrease in the availability of grasshoppers and beetles (Flake 1973).  Captives that were offered a diet of red meat, seeds, and beef fat, were shown to rarely choose beef fat until after a week of cold weather when they ate the fat almost exclusively (Jahoda 1970).  This shift in preference was associated with an increased need of calories during cold weather (Jahoda 1970).  Onychomys leucogaster is very capable of killing other mice and lizards, usually by a piercing bite to the brain and sometimes by strangulation (Egoscue 1960).  They can easily pick up and carry prey almost as large as themselves (Egoscue 1960).

Reproduction: Females usually require six months or more to reach breeding age, after which they are polyestrous from January through July (Egoscue 1960).  Parturition precedes estrus by only a few hours to a day or two (Egoscue 1960).  The gestation period for non-lactating females is 32 days and 33 to 47 days for lactating females (Svihla 1936).  Litter size ranges from 1 to a maximum number of 6 (Egoscue 1960; Egoscue et al. 1970).  They usually produce 3 to 6 litters each year (Egoscue 1960).  At birth, ears and eyes are closed (Svihla 1936).  Their ears unfold around the third day and the auditory meatus opens on day 14 (Svihla 1936; Horner 1968).  Their eyes open at 19-20 days, they are weaned after 24 days, and they leave the nest shortly afterwards (Svihla 1936).  Males become sexually active around four months of age and breed until they are around 24 months old (Pinter 1970).  Females usually breed until they are around 19 months old (Pinter 1970).

Behavior: Onychomys leucogaster are usually nocturnal and show a timodal circadian pattern (Egoscue 1960; Johoda 1973).  They are active more during the new moon than any other time of the month. During the time of the full moon, they are out of the nest noticeably less often (Johoda 1973). 

Onychomys leucogaster uses nest burrows for sleeping, retreat, rearing young, caching food and some feeding (Ruffer 1965b).  Nest burrows are dug by male-female pairs of mice (Ruffer 1965b).  The male digs by standing on his hindlegs, scooping sand under his belly with his forefeet, and occasionally holding himself up with his forefeet and kicking sand back with his hindfeet (Ruffer 1965b).  The female follows behind him, moving the sand on out of the burrow (Ruffer 1965b).  Working together, the pair can finish the burrow in about 5 minutes (Ruffer 1965b).  They do not use burrows of other species for nesting, but for retreat only, always moving on to dig their own burrow (Ruffer 1965b).  They are extremely territorial defending an area of undetermined size around their burrows (Ruffer 1968).

Much has been said about the call of Onychomys leucogaster.  They howl like wolves and can be heard at a distance of at least 100 feet (Svihla 1936).  This shrill note is said to have twice the frequency of the highest note of the piccolo (Hildebrand 1961).  Other sounds include barking and chirping usually made in protest while feeding or being caught in traps (Egoscue 1960).

Onychomys leucogaster has been observed swimming by “dog-paddling,” carrying its head above the water (Russell and Finley 1954).

Habitat:  Onychomys leucogaster is generally found in semiarid scrub deserts (Pinter 1970).  They are common on semi-stabilized sand dunes along valley floors and foothills with vegetation consisting of four-winged saltbrush (Atriplex canescens), rabbit brush (Chrysothamnus sp.), buckwheat (Erigonum dubium), horsebrush (Tetradymia sp.), greasewood (Sarcobatus vermiculatus), Indian rice grass (Oryzopsis hymenoides), and other grasses and herbs (Egoscue 1960).  They tend to avoid marshy areas, rocky situations, and precipitous hillsides (Egoscue 1960).  The most important requirement for habitat selection is adequacy for frequent dust bathing (Egoscue 1960).  Grasshopper mice that are not allowed to dust bathe do not thrive because their fur becomes oily and uncomfortable (Egoscue 1960).

 The economic status of Onychomys leucogaster is either neutral or beneficial since they feed on pests such as insects and small mice (Davis and Schmidly 1994).

Conservation Status:

No literature was found to say that Onychomys leucogaster is rare, threatened or endangered.

References:

Davis, William B., and David J. Schmidly.  1994.  The mammals of Texas. University of Texas Press, Austin.

Egoscue, H. J.  1960.  Laboratory and field studies of the northern grasshopper mouse.  Journal of Mammalogy 41:99-110.

Egoscue, H. J.  1963.  Color phases and their inheritance in the northern grasshopper mouse.  Journal of Mammalogy 44:74-79.

Egoscue, H. J., J. G. Bittemenn, and J. A. Petrovich.  1970.  Some fecundity and longevity records for captive small mammals.  Journal of Mammalogy 51:622-623.

Flake, L. D.  1973.  Food habits of four species of rodents on a short-grass prairie in Colorado.  Journal of Mammalogy 54:636-647.

Goldman, E. A.  1939.  Nine new mammals from islands in Great Salt Lake, Utah.  Journal of mammalogy 20:351-357.

Hansen, R. M.  1975.  Plant material in the diet of Onychomys.  Journal of Mammalogy 56:530-531.

Hildebrand, M.  1961.  Voice of the grasshopper mouse.  Journal of Mammalogy 42:263.

Horner, B. E.  1968.  Gestation period and early development in Onychomys leucogaster breviauritus.  Journal of Mammalogy 49:513-515.

Jahoda, J. C.  1970. Seasonal change in food preference of Onychomys leucogaster breviauritus.  Journal of Mammalogy 51:197.

Johoda, J. C.  1973.  The effect of the lunar cycle on the activity pattern of Onychomys leucogaster breviauritus.  Journal of Mammalogy 54:544-549.

McCarty, R.  1978.  Onychomys leucogaster.  Mammalian Species 87:1-6.

Pinter, A. J.  1970.  Reproduction and growth for two species of grasshopper mice (Onychomys) in the laboratory.  Journal of Mammalogy 51:236-243.

Ruffer, D. G.  1965a. Juvenile molt of Onychomys leucogaster.  Journal of Mammalogy 46:338-339.

Ruffer, D. G.  1965b. Burrows and burrowing behavior of Onychomys leucogaster.  Journal of Mammalogy 46:241-247.

Ruffer, D. G.  1968.  Agonistic behavior of the northern grasshopper mouse (Onychomys leucogaster breviauritus).  Journal of Mammalogy 49:481-487.

Russell, R. J., and F. S. Finley.  1954.  Swimming ability of the grasshopper mouse.  Journal of Mammalogy 35:118.

Svihla, R. D.  1936.  Breeding and young of the grasshopper mouse (Onychomys leucogaster fuscogriseus).  Journal of Mammalogy 17:172-173.