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Dark kangaroo mouse
These kangaroo mice are found in the Great Basin region of
western United States, including Oregon, Utah, California, and
Nevada.
Kangaroo mice are found among bushes growing in soils covered with
gravel or on sand dunes. The altitude of the habitat is around
1,190-2,455 meters. Burrows are constructed in soft ground with the
entrance near a shrub. Burrows have simple, unbranched tunnels,
elaborate nests, and a food storage room. A small territory is
maintained near the burrow, but an individual's home ranges may
overlap with those of several other individuals. Average home range
for males is 6,613 square meters and 3,932 for females.
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Dark kangaroo mouse
Total length measures 140-177 mm, head and body length is 66-77 mm,
tail length 68-103 mm, and the hind foot is 23-27 mm long. The head
is large in proportion to their body size due to the inflation of
the tympanic bullae that extends to the upper portion of the
cranium. The neck is fairly short. Upper parts are brownish to
grayish black. Compared to the similar looking species, M. pallidus,
M. megacephalus have basally plumbeous and white-tipped under parts,
and the end of the tail is blackish. The distal half of the tail is
darker than the proximal. The tail is not crested nor does it end in
a tassel; however, it is thick and stores fat. The fat in the tail
is used as a source of energy during dormancy.
The pelage is relatively long, silky, and lax. The hind feet are
covered with stiff hairs on the sides, which increases the surface
of the fine and soft feet. The undersurface of the hind feet are
also well furred. The feet functions similar to a sand shoe in a
desert.
Kangaroo mice utilize their forelegs more than kangaroo rats when
running.
Compared to those of kangaroo rats, the molars of kangaroo mice do
not constantly regrow. The base of the zygomatic arch is not
enlarged as it is in kangaroo rats.
Several features, including long hind legs, relatively small
forelegs, long vibrissae, and enlarged auditory bullae are probably
adaptations to the jumping mode of locomotion.
Reproduction
Females are polyestrous. Pregnant individuals have been found from
March to September. The majority of the young are born in May and
June. Litter size ranges from 2 to 7 with an average of 3.9. A study
done in west-central Nevada showed that the population consisted of
2:1 sex ratio favoring males. A successful reproduction has yet to
be recorded in captivity. Maximum longevity (of an individual
trapped in the wild) is five years and five months.
Behavior
Microdipodops megacephalus are primarily bipedal, using large and
powerful hind legs for locomotion. The small forelegs are scarcely
used in moving. The tail, if used at all, functions as a balancing
device. Upright posture is also used in defending territory and
in fleeing from danger. During nest defense, kangaroo mice make high
pitched squeals. These kangaroo mice sleep on their backs with their
forelimbs stretched over their heads and the hind limbs tucked on
the belly. They are nocturnal and extremely sensitive to light. When
exposed to a light, they seek shelter under the darkest spot
available.
Peak activity occurs in the first two hours after sunset. Moonlight
and temperature are additional factors affecting the activity of the
kangaroo mice. Activity reaches its peak under partly cloudy skies,
and ceases during rain. Activity is only observed from March to
October, suggesting the kangaroo mice may hibernate.
Kangaroo mice are solitary animals and are aggressive toward one
another. Cannibalism has been recorded when two individuals were
kept together. Other laboratory studies showed that adults avoid one
another or stay together for only one or two nights. Kangaroo mice
can be easily kept in captivity.
Food Habits
These kangaroo mice are normally granivorous, although they feed on
insects, particularly during summer when their activity reaches its
maximum. The shift in diet may be caused by competition for food
with pocket mice. Kangaroo mice store food in seed caches found in
their burrows. 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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