Although not endangered, numbers of M. minutus have been greatly reduced by modern agricultural methods, such as combine harvesting, spraying, earlier harvesting, and stubble burning. They also seem to have a three-year pattern of population increase and decline. Every third year, the population apparently crashes, only to be rebuilt over the next two years. It is unclear why this happens. (Burton 1969; Fact-File; Macdonald 1985)
IUCN Red List of Threatened Species: least concern
M. minutus a small mouse, ranging in size from 55 to 75 mm long, with a tail that is usually 50 to 75 mm long. It has large eyes and ears, which permits it to see the slightest motions and hear the faintest sounds in the darkness. It has a small, blunt nose encircled by vibrissae. The fur is soft and thick, with the upper parts of the body a brownish color with a yellowish or reddish tinge, and the under parts white to buffy colored. The prehensile tail is bicolored and lacks fur at the very tip, and the feet are fairly broad. The feet are specially adapted for climbing, with the outer of the five toes on each foot being large and more-or-less opposable. This mouse can grip a stem with each hindfoot and its tail, leaving the forepaws free for collecting food. It can also use its tail for balance as it scurries along long grass stems. The fur is somewhat thicker and longer in the winter than in the summer. As with other members of its subfamily, M. minutus has moderately low crowned teeth with rounded cusps on the biting surface arranged in three longitudinal rows. The masseter muscle, as well as the lateral muscle of the jaw, are moved forward on the maxillary, providing very efficient, effective gnawing action. The auditory bullae are large, and it is thought that the size of these resonating chambers enables the mouse to detect low frequency sounds carried over great distances, and thus be better able to escape predation. (Burton 1969; Grzimek 1990; Macdonald 1985; Nowak 1983)
Other Physical Features: endothermic ; bilateral symmetry
Average mass: 6 g.
Average basal metabolic rate: 0.201 W.
Average lifespan
Status: wild: 1.5 years.
Average lifespan
Status: captivity: 5.0 years.
Average lifespan
Status: captivity: 4.0 years.
M. minutus lives in tropical and subtropical regions and prefers habitats characterized by tall grasses. These would include high meadows, reed grass plots, bushland interspersed with grasses,and grain fields. In Italy and East Asia, they also make a home in rice fields. Population density may be very high in favorable environments. Originally, these mice lived in humid regions with high, long-lasting grasses growing near rivers, ponds, and lakes. With the advent of human encroachment, however, M. minutus has been forced to live along roadsides and in crop fields. When the farmer clears his land for the harvest, this mouse is left homeless. The problem is solved by the mouse either forming a shallow burrow in the soil, or finding shelter in the barn or silo. Not all mice are so lucky, however, and many mice die after being rendered homeless. (Grzimek 1990; Fact-File)
Terrestrial Biomes: savanna or grassland
M. minutus lives throughout Europe and northern Asia. Distribution ranges from northwest Spain through most of Europe, across Siberia to Korea, north to about 65 degrees in Russia, south to the northern edge of Mongolia. There are also isolated populations in southern China west through Yunnan. (Wilson 1993)
Biogeographic Regions: neotropical (Native )
M. minutus eats a variety of seeds, especially grasses, fruit and grain. In the summer, its diet also contains insects and larvae, such as moths, caterpillars, and grasshoppers. It is a very opportunistic feeder and eats whatever is available during the season. In winter, when food is scarce, M. minutus takes advantage of human stores of food and is often found in grain silos or haystacks. In order to facilitate cellulose digestion, these rodents have a large cecum which contains large amounts of bacteria. After the food has been softened and partially digested in the stomach, it passes down through the large intestine and into the cecum, There the cellulose is broken down into digestable carbohydrate constituents. However, absorption can only take place higher in the gut and in the stomach. For this reason, rodents reingest the soft pellets of bacterially digested food after having defecated it. This reingestion allows the digestive system to be highly efficient, assimilating 80 percent of the ingested energy. (Fact-File; Grzimek 1990; Macdonald 1985; Nowak 1983)
In the wild, M. minutus helps keep populations of crop pests down to a manageable level. (Fact-File; Macdonald 1985)
M. minutus consume large amounts of crop yields, either by eating the seeds in the field or feeding on carefully stored grains. Rodent-borne diseases have also been a large influence on the human population, taking more human lives than all wars and revolutions put together. (Macdonald 1985)
Perception Channels: tactile ; chemical
The female gives birth to an average litter of 5 to 6 young after a gestation period of 21 days. Births take place in "high nests", structures built about 100 to 130 cm above the ground. Construction on these nests begins during the spring and summer breeding season, and one nest is built for each litter of young. These nests are globular in shape, about 60 to 130 mm in diameter. They are formed of three layers of grass blades woven tightly together. The lining consists of finely shredded leaves and grass, which form a soft warm nest for the young. There is often more than one entrance, but these holes are kept closed by the female during the first week after parturition, and males are not allowed into the nest at all. Reproduction is usually concentrated during warmer, drier months, starting around April and ending in September. Females are polyestrous, undergo a postpartum estrus, and under the correct favorable conditions, can give birth several times in rapid succession. Because they have a short natural longevity, females usually live through only one or two reproductive seasons in a lifetime, but in captivity they have been known to experience up to nine. Gestation is about 17-18 days, as is the typical minimum interval between litters. The number of young per litter ranges from 1 to 13, but is usually around 3 to 8. The young weigh about a gram at birth, and are 2 cm long. The young are born naked, blind and altricial, but can hold onto a grass stalk as early as three days after birth. They open their eyes at 8 to 10 days, are weaned and leave the nest at 15-16 days, and reach sexual maturity in 35 days. Maximum known longevity in the wild is 16 to 18 months, with few individuals living past 6 months. In captivity, M. minutus can live to be just under 5 years old. (Burton 1969; Grzimek 1990; Nowak 1993)
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual
Average birth mass: 0.9 g.
Average gestation period: 20 days.
Average number of offspring: 5.2.
Average age at sexual or reproductive maturity (male)
Sex: male: 37 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 40 days.
The harvest mouse (Micromys minutus) is a small rodent native to Europe and Asia. It is typically found in fields of cereal crops, such as wheat and oats, in reed beds and in other tall ground vegetation, such as long grass and hedgerows. It has reddish-brown fur with white underparts and a naked, highly prehensile tail, which it uses for climbing. It is the smallest European rodent; an adult may weigh as little as 4 grams (0.14 oz). It eats chiefly seeds and insects, but also nectar and fruit. Breeding nests are spherical constructions carefully woven from grass and attached to stems well above the ground.
The genus Micromys most likely evolved in Asia and is closely related to the long-tailed climbing mouse (Vandeleuria) and the pencil-tailed tree mouse (Chiropodomys).[2] Micromys first emerged in the fossil record in the late Pliocene, with Micromys minutus being recorded from the Early Pleistocene in Germany.[3] They underwent a reduction in range during glacial periods, and were confined to areas in Europe that were free of ice. During the mid-Pleistocene, Micromys minutus specimens also lived in parts of Asia.[4][5][6] This suggests that they spread towards Asia when the ice sheets started to melt. Other evidence suggests that Micromys minutus could have been introduced accidentally through agricultural activities during Neolithic times.[7]
Before the harvest mouse had been formally described, Gilbert White reported their nests in Selborne, Hampshire:
They never enter into houses; are carried into ricks and barns with the sheaves; abound in harvest; and build their nests amidst the straws of the corn above the ground, and sometimes in thistles. They breed as many as eight at a litter, in a little round nest composed of the blades or grass or wheat. One of these nests I procured this autumn, most artificially platted,[8] and composed of the blades of wheat; perfectly round, and about the size of a cricket-ball. It was so compact and well-filled, that it would roll across the table without being discomposed, though it contained eight little mice that were naked and blind.[9]
Tennis balls used in play at Wimbledon have been recycled to create artificial nests for harvest mice.[10]
The harvest mouse ranges from 55 to 75 mm (2.2 to 3.0 in) long, and its tail from 50 to 75 mm (2.0 to 3.0 in) long; it weighs from 4 to 11 g (0.14 to 0.39 oz),[11][12] or about half the weight of the house mouse (Mus musculus). Its eyes and ears are relatively large. It has a small nose, with short, stubble-like whiskers, and thick, soft fur, somewhat thicker in winter than in summer.[13]
The upper part of the body is brown, sometimes with a yellow or red tinge; the under-parts range from white to cream coloured. It has a prehensile tail which is usually bicoloured and furless at the tip. The mouse's rather broad feet are adapted specifically for climbing, with a somewhat opposable, large outermost toe, allowing it to grip stems with each hindfoot and its tail,[13] thus freeing the mouse's forepaws for food collection. Its tail is also used for balance.
The harvest mouse is common in all east coast counties of England, reaching the North York Moors. It also inhabits less favourable habitats, such as woodlands and forests in the west.[7]
Harvest mice reside in a large variety of habitats, from hedgerows to railway banks. Harvest mice seem to have an affinity for all types of cereal heads, except for maize (Zea mays). Harvest mice typically like using monocotyledons for their nest-building, especially the common reed (Phragmites australis) and Siberian iris (Iris sibirica).[7] Most harvest mice prefer wetlands for their nesting habitats.[14][15]
Harvest mice in Japan like making wintering nests near the ground from grasses that are dried, which indicates that they require vegetative cover in the winter, as well as in the warmer seasons.[16] Grasslands with a mix of perennials and annual grasses are required to balance the increases in nesting periods and the mice's need to secure nutrients. Habitat selection might be the result of differences in the structure of the landscape of grasslands and wetlands in the area.[17]
Harvest mice have a short lactation period of 15-16 days.[18] They spend most of their life in long grass and other vegetation such as reedbeds, rushes, ditches, cereals and legumes. They are very skilled at climbing among grasses due to their tail. They grasp leaves and stems with their feet and tail, which leaves their hands free for other tasks. These tasks can include grooming and feeding. Harvest mice have a prehensile tail that functions as an extra limb during climbing.[19] During the lactation period, the pups are able to climb a vertical bar by the time they first emerge from their nest. At 3-7 days they learn hand grasping, and at 6-9 days they learn food grasping. Between 6-11 days, they adopt a quadrupedal stance, and at 10-11 there is tail prehension, and righting at 10-12 days. The righting response in harvest mice develops earlier, but takes longer to master than the other skills the pups learn. They cannot climb horizontally by the time they are weaned, suggesting that horizontal climbing is not as essential as vertical climbing.[20]
Their predators include domesticated cats, barn owls, tawny owls, long-eared owls, little owls, and kestrels.[7]
These rodents are sometimes kept as pets due to their small size, they are very easy to care for, they require low maintenance and to be kept in groups.[21]
In most rodent species, females prefer familiar males to unfamiliar ones.[22] The adaptive preference of mating with familiar males is not uncommon as familiarity is a proxy for quality that is seen in many solitary animals.[23] Harvest mice are thought to be solitary, and the females prefer for familiar males over unfamiliar.[24] There is no size dimorphism between the sexes[25] so the females are considered dominant over the males. Females do not show interest in the male's odor. When females are in oestrus they spend more time with familiar males, and prefer the one that is heavier. While in dioestrus, the female spends more time with unfamiliar males.[24]
In most years in Britain, harvest mice build their first breeding nests in June or July; occasional nests are built earlier in April or early May. They prefer building their breeding nests above ground.[26] In Russia, harvest mouse breeding occurs in November and December in cereal ricks, buckwheat, and other cereal heads.[27]
Due to their habitat, in Japan harvest mice are threatened by a number of anthropogenic effects such as farming, pesticide use, crop rotation, habitat destruction, fragmentation, and wetland draining. Grasslands in that country are rapidly decreasing in area, and are also becoming increasingly fragmented.[17]
The first survey of the harvest mouse in Britain was conducted by the Mammal Society in the 1970s,[28] and later followed up by the National Harvest Mouse survey in the late 1990s. These surveys indicated that harvest mouse nests were on a decline with 85% of the suitable habitat no longer available for the mice.[29]
As of 2019 the harvest mouse is protected under the 1981 Wildlife and Countryside Act of 1981[30] and the UK Post-2010 Biodiversity Framework: Implementation Plan.[31]
The harvest mouse (Micromys minutus) is a small rodent native to Europe and Asia. It is typically found in fields of cereal crops, such as wheat and oats, in reed beds and in other tall ground vegetation, such as long grass and hedgerows. It has reddish-brown fur with white underparts and a naked, highly prehensile tail, which it uses for climbing. It is the smallest European rodent; an adult may weigh as little as 4 grams (0.14 oz). It eats chiefly seeds and insects, but also nectar and fruit. Breeding nests are spherical constructions carefully woven from grass and attached to stems well above the ground.
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