Communication patterns have not been reported for these mice. It is likely that they communicate with conspecifics with a combination of olfactory/chemical cues, vocalizations, and tactile communication, as these avenues of communication are prevalent in rodents.
Communication Channels: visual ; tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
These mice are thought to be quite common, and not in danger. However, Canada considers R. megalotis vulnerable because it lives in grasslands. Grasslands are a threatened habitat. Also, there is little known about Canadian populations of Western harvest mice.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
There are no reports of these mice actually damaging crops. However, human agriculture has positively affected R. megalotis, allowing it to extend its geographic range eastward.
There is no known benefit of this species for humans. However, because they are important in the food web, many of the higher profile animals that people enjoy watching, such as hawks, owls, coyotes, and foxes, rely on them.
This species is essential to western ecosystems. It reproduces rapidly, and lives a very short time, even when removed from the threat of predation. This indicates that the species does not live long in the wild. The most likely source of mortality is predation.
As a prey species, the availability of R. megalotis likely controls the populations of many predators which rely heavily upon this species in their prey base.
Also, because R. megalotis caches seeds, it probably helps in their dispersal.
Ecosystem Impact: disperses seeds; keystone species
The primary diet of this mouse is seeds. However, it eats anything available at the time, including new growth of plants and insects (grasshoppers and moths). These animals sometimes cache food in their nests. Reithrodontomys megalotis drinks water.
Animal Foods: insects
Plant Foods: leaves; seeds, grains, and nuts; fruit; flowers
Foraging Behavior: stores or caches food
Primary Diet: herbivore (Granivore )
Reithrodontomys megalotis is found over a wide portion of the western United States of America and central Mexico. It is broadly distributed from the Great Lakes to the Pacific Coast. It occurs at elevations from Death Valley, California (below sea level), to 4000 m on the Popocatepetl and Orozaba volcanoes in Central Mexico.
Biogeographic Regions: nearctic (Native )
Reithrodontomys megalotis is found in a variety of open areas, including grasslands, prairies, meadows, and marshes. It also inhabits more arid areas such as deserts, sand dunes, and shrublands.
Range elevation: -77 to 4000 m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: desert or dune ; chaparral ; forest ; scrub forest ; mountains
Wetlands: marsh
Other Habitat Features: urban ; suburban ; agricultural ; riparian
Only a few individual reach at the age of 1 year. The maximum reported lifespan for this species is 18 months.
Range lifespan
Status: wild: 18 (high) months.
Typical lifespan
Status: wild: 12 (high) months.
This mouse is slender, long-tailed, and has large, naked ears. These mice range in length from 118 to 170 mm. The tail is shorter than the body, measuring between 50 and 96 cm. Western harvest mice typically weigh between 8 and 17 g. The upper incisors have distinct lengthwise grooves. There is no apparent difference in size or coloration between males and females.
The color of the fur on the back ranges from pale-gray to brown, and the fur on the belly ranges from white to deep gray. There is a dark stripe down the middle of the back and along the forehead. There are 3 pelages categories: juvenile, sub-adult, and adult. The juvenile pelage is relatively short and woolly, with grayish brown color. Sub-adult pelage is longer, thicker, and brighter than that of a juvenile. Adult pelage is characterized by one of two patterns. The summer pelage is short and sparse, with brown above and grayish below. The stripe down the back is not clearly demarcated in the summer pelage. The winter pelage, in contrast, is thicker, longer, and paler than the summer pelage.
Range mass: 8 to 17 g.
Range length: 118 to 170 mm.
Average length: 140 mm.
Sexual Dimorphism: sexes alike
Other Physical Features: endothermic ; bilateral symmetry
Average basal metabolic rate: 0.13 W.
Because of its small size and abundance, R. megalotis is an important prey species. There are many predators of the western harvest mouse, including owls, hawks, snakes, canids, mustelids, felids, and scorpions.
Because of their noctural activity, it is likely that these mice have the best opportunity of avoiding predation by nocturnal predators. These mice are most active on very dark nights, which may be a strategy for avoiding predation by animals that use vision to detect prey.
Known Predators:
Reithrodontomys megalotis is a polygynous species, in which the dominant male mates with females during their estrus period.
Mating System: polygynous
Few individuals live more than a year. As would be predicted from this short lifespan, young reach sexual maturity early, at about 1 month of age, and full maturity is reached at about 4 to 5 months. This species breeds from early spring to late autumn, foregoing reproduction only in the most severe winter weather.
Females have a high reproductive potential, having early sexual maturity and short gestation period of 23 to 25 days. The average litter size varies geographically, but is around 4, and as many as 9 pups can be born at one time.
Newborns are born naked, pink and blind. Neonates weigh 1 to 1.5 g, are 7 to 8 mm in length, and are totally helpless. They have a slight coating of fur by the time they start to crawl, around 5 days of age. Their incisiors erupt around this time. The eyes and ears are open by around 11 days of age. The young are weaned by 24 days. Young are reported to leave their natal nest around 3 weeks of age.
Reithrodontomys megalotis is known to undergo a post partum estrus cycle, allowing rapid production of litters. As females reach the age of approximately 45 weeks, there is a reduction in litter size, signalling senility.
Breeding interval: Breeding interval varies geographically, with animals in mild climates breeding approximately once per month, year round.
Breeding season: Wild western harvest mice breed from early spring to late autumn, foregoing reproduction only in the worst of winter weather..
Range number of offspring: 1 to 9.
Average number of offspring: 4.
Range gestation period: 23 to 25 days.
Average weaning age: 24 days.
Average time to independence: 3 weeks.
Average age at sexual or reproductive maturity (female): 4 to 5 months.
Average age at sexual or reproductive maturity (male): 4 to 5 months.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous ; post-partum estrous
Average birth mass: 1.33 g.
Average number of offspring: 3.3.
Average age at sexual or reproductive maturity (male)
Sex: male: 80 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 107 days.
Females care for their young in a nest made of grass, nursing them for up to 24 days. The young are born blind and helpless, but grow quickly. The young can leave their natal nest as early as three weeks of age. Males apparently play no role in parental care.
Parental Investment: altricial ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)
The western harvest mouse (Reithrodontomys megalotis) is a small neotomine mouse native to most of the western United States.[3] Many authorities consider the endangered salt marsh harvest mouse to be a subspecies, but the two are now usually treated separately.[1]
Its range extends from southwest British Columbia and southeast Alberta continuously to west Texas, northeast Arkansas, northwest Indiana, southwest Wisconsin, and the interior of Mexico to Oaxaca.
The harvest mouse has brownish fur with buff sides, a white belly, and an indistinct white stripe on the fur along the spine. Adults grow up to 11 to 17 centimetres (4.3 to 6.7 in) in length with a tail length of 5 to 10 centimetres (2.0 to 3.9 in). Their height (from the ground to the highest point of their back) is between 1.5 and 2.0 centimeters. A mature mouse weighs anywhere from 9 to 22 grams (0.32 to 0.78 oz). There is no sexual dimorphism in this species.[4]
Similar species are the plains harvest mouse (Reithrodontomys montanus), which has a more distinct but narrower stripe on its spine, and the fulvous harvest mouse (R. fulvescens), which has a longer tail. Also similar is the salt marsh harvest mouse (R. raviventris), which has an underbelly fur that is more pinkish cinnamon to tawny. Finally, the house mouse (Mus musculus) has incisors without grooves, unlike those of the western harvest mouse. The dental formula of R. megalotis is 1.0.0.31.0.0.3 = 16.[5]
The mouse is nocturnal, with particularly intense activity on very dark nights. This mouse is particularly resourceful, making use of the ground runways of other rodents. It is also a very agile climber. Once temperatures reach a certain degree, the western harvest mouse goes into torpor, but scientists have yet to determine if it goes into true hibernation. This mouse builds spherical nests that are about 125mm in diameter. These nests can be found on the ground or under trees, logs, or plants that aid in protection from predators. Nests can also be found above ground or in burrows. There are usually one or more access points at the base of the nest.[6]
The western harvest mouse is an herbivore with a diet consisting of mainly seeds and grains from various plants. These plants include: fruits, vetch, blue grass, fescue, oats, and brome grass.[6] In preparation for autumn and winter, the western harvest mouse stores its food along runways created throughout fields that it occupies and in underground vaults.[5] Although its primary food source is seeds, springtime dining is augmented with new plant growth. In June, July and August the mouse is known to consume certain insects, especially grasshoppers and caterpillars.
Breeding nests are spherical constructions woven from grass or other plant material. A nest is approximately 13 centimeters in diameter and lined with a more downy material of fibrous plants. A nest may have one or more entrances near its base. Most commonly, the nest is built on the ground in a protected area such as within a shrub or beside a fallen tree. However, the mouse will occasionally place the nest above-ground within a shrub.
It breeds from early spring to late autumn, with reduced activity at midsummer. The gestation period is 23 to 24 days. Repeated fertilization often occurs immediately after giving birth. It is not uncommon for a female to have ten to fourteen litters per annum, with a typical litter size of two to six individuals. However, litters of up to nine offspring can occur. Thus an annual production of forty to sixty young per female is normal. Newborn mice weigh approximately 1.0 to 1.5 grams.[6]
Domestic and feral cats are a threat to the western harvest mouse.[4] On the IUCN Red List it is listed as "Least Concern" (LC). Its many predators include the fox, weasel, coyote, hawk, snake and owl species. Other predators include shrikes, squirrels, raptors, short-tailed shrews, cats, and scorpions.[6]
The western harvest mouse (Reithrodontomys megalotis) is a small neotomine mouse native to most of the western United States. Many authorities consider the endangered salt marsh harvest mouse to be a subspecies, but the two are now usually treated separately.
