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1990-07-22
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Season by Season
In a few %F,10,g\environm%environments around the
world--such as tropical %F,10,h\rain%rain
%F,10,h\rain%forests --the climate changes little
from one season to the next. Food is
usually available all year long. The
lives of %F,10,h\mammal%mammals that inhabit these
areas also remain much the same
whatever the season. Where the
seasons do change, however, mammals
must %F,10,g\adapt%adapt their behavior. They must
be able to get food and shelter in
different kinds of weather.
Many mammals store food in the
summer and fall. %F,10,h\rodent%Rodents often put
away nuts and seeds in their
%F,10,g\burrow%burrows. During the winter, when
fresh food is scarce, they eat what
they have saved. The pika builds
haystacks. It gathers herbs and
grasses and spreads them out to dry.
Then it piles the dry food under
rock ledges for use during the
winter.
Some mammals, such as marmots and
dormice, get along during cold
weather by means of %F,10,g\hibernat%hibernation (say
hye-bur-NAY-shun). A hibernating
animal eats a great deal during the
summer and fall and grows fat. When
winter comes, it crawls into a
burrow or %F,10,g\den%den and drops into a kind
of sleep. Its body temperature goes
down, and its breathing and heart
rate slow. It uses only a small part
of the energy it would need if it
were active. It lives on the fat in
its body. Animals that behave
similarly in hot or dry weather are
said to %F,10,g\aestivat%aestivate (say ES-tuh-vate).
Mammals that live in cool climates
usually have two different coats of
hair. Their thick winter coat serves
as insulation, keeping body heat in
and cold out. This heavy coat is
shed in warm weather. It is replaced
by a thinner summer coat. This
process is called %F,10,h\molt%molting.
A few mammals, such as the
snowshoe hare and some weasels,
change color as the seasons change.
In summer, their hair is brown.
Gradually, new white hair grows in.
By winter, the summer hair has been
shed, and the coats are white. The
color changes help %F,10,g\camoufla%camouflage the
animals. Their white coats blend in
with snow. Their brown coats are
hard to see against rocks and dry
grasses.
Some mammals escape harsh winters
by %F,10,h\migratio%migrating, or traveling, from one
place to another. In the summer,
mountain sheep feed high in the
mountains. They come down to lower
areas during cold weather. Certain
whales swim to warmer water in
winter. They spend only the summer
months in the polar regions.