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Eurasian harvest mouse
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.
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Eurasian harvest mouse
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.
Reproduction
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.
Behavior
These tiny mice are moderately sociable. They live in small,
overlapping home ranges. Population numbers fluctuate over the years
and seasonally, generally peaking around autumn. While population
density typically remains around 100 to 200 individuals per hectare,
it has been observed that as many as 5,000 individuals may
congregate in a barn or grain storage area during the winter. They
merely tolerate each other at this time, becoming more agressive
towrad one another as warm weather approaches. If captive males are
placed together they will fight fiercely. Adults of opposite sexes
come together only to mate and construct a breeding nest, then the
female drives the male away. Nonbreeding individuals may also
construct breeding nests, but they are less sturdy and lack the
inner lining. During the cooler months, M. minutus may build a
sleeping nest out of a mass of grass blades shredded lengthwise and
laid on the ground or in a shallow burrow if it cannot find a more
adequate shelter. This mouse does not hibernate. It is active in
spurts of time throughout the day and night, with a three hourly
rhythm of alternating sleeping and eating throughout each 24 hour
day. Every third hour, it feeds for half an hour, while the rest of
the time it spends sleeping. In order to escape enemies, M. minutus
moves slowly, and incorporates "camouflage posture" as a defense,
where it remains motionless against the stalk of the grass. If
danger persists, the mouse lets itself drop into the darkness of the
ground level.
Food Habits
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.
In captivity they should be offered a complete diet of rodent lab blocks, and rat or mouse
mix, with bits of fruit or veggies regularly. Cheerios or wheat
bread are great treats, in small quantities. Do NOT feed chocolate,
fried foods, salted foods, candy or junk food! They may enjoy
crickets and mealworms if they are captive bred, never feed wild
insects as they may carry parasites. Vitamins, like Nutri-Cal are a good addition to their diet, and added calcium
during nursing and growth due to demands on their systems at those
times, but take care not to overdo it. Water bottles should be used
to proved constant, clean water. Ceramic or stoneware food dishes
work well for keeping seeds or fresh foods off the floor, and a wire
mesh hopper that allows them to eat the lab blocks through without
extra waste.
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