HOW DO ANIMALS SPEND THE WINTER?

(excerpts only)


by

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INDEX: How do animals spend the winter? - hibernate, migrate, adapt


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Projects

Learn More About: hibernation

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HOW DO ANIMALS SPEND THE WINTER?




The weather gets colder, days get shorter and leaves turn color and fall off the
trees. Soon, winter is here. Snow covers the ground. People live in warm houses
and wear heavy coats outside. Our food comes from the grocery store. But what happens
to the animals?




MIGRATE



Animals do many different, amazing things to get through the winter. Some of them
"migrate." This means they travel to other places where the weather is warmer or they can find food.
Many birds migrate in the fall. Because the trip can be dangerous,
some travel in large flocks. For example, geese fly in noisy, "V"-shaped groups.
Other kinds of birds fly alone.
How do they know when it is time to leave
for the winter? Scientists are still studying this. Many see migration
as part of a yearly cycle of changes a bird goes through. The cycle is
controlled by changes in the amount of daylight and the weather. Birds can fly very long distances. For example, the Arctic tern nests close to the
North Pole in the summer. In autumn, it flys south all the way to Antarctica. Each
spring it returns north again.
Most birds migrate shorter distances. But
how do they find their way to the same place each year? Birds seem to
navigate like sailors once did, using the sun, moon and stars for
direction. They also seem to have a compass in their brain for using
the Earth's magnetic field.
Other animals migrate, too. There are a few mammals, like some bats, caribou and
elk, and whales that travel in search of food each winter. Many fish migrate. They
may swim south, or move into deeper, warmer water.
Insects also migrate. Some butterflies and
moths fly very long distances. For example, Monarch butterflies spend
the summer in Canada and the Northern U.S. They migrate as far south as
Mexico for the winter. Most migrating insects go much shorter
distances. Many, like termites and Japanese beetles, move downward into
the soil. Earthworms also move down, some as far as six feet below the
surface.

ADAPT



Some animals remain and stay active in the winter.
They must adapt to the changing weather. Many make changes in their
behavior or bodies. To keep warm, animals may grow new, thicker fur in
the fall. On weasels and snowshoe rabbits, the new fur is white to help
them hide in the snow.
Food is hard to find in the winter. Some
animals, like squirrels, mice and beavers, gather extra food in the
fall and store it to eat later. Some, like rabbits and deer, spend
winter looking for moss, twigs, bark and leaves to eat. Other animals
eat different kinds of food as the seasons change. The red fox eats
fruit and insects in the spring, summer and fall. In the winter, it can
not find these things, so instead it eats small rodents. Animals may find winter shelter in holes in trees or logs, under rocks or leaves,
or underground. Some mice even build tunnels through the snow. To try to stay warm,
animals like squirrels and mice may huddle close together.
Certain spiders and insects may stay active if they live in frost-free areas and can
find food to eat. There are a few insects, like the winter stone fly, crane fly,
and snow fleas, that are normally active in winter. Also, some fish stay active in
cold water during the winter.





HIBERNATE



Some animals "hibernate" for part or all of the
winter. This is a special, very deep sleep. The animal's body
temperature drops, and its heartbeat and breathing slow down. It uses
very little energy. In the fall, these animals get ready for winter by
eating extra food and storing it as body fat. They use this fat for
energy while hibernating. Some also store food like nuts or acorns to
eat later in the winter. Bears, skunks, chipmunks, and some bats
hibernate.


AND MORE



Cold-blooded animals like fish, frogs, snakes and turtles have no way to keep warm
during the winter. Snakes and many other reptiles find shelter in holes or burrows,
and spend the winter inactive, or dormant. This is similar to hibernation.
Water makes a good shelter for many animals. When the weather gets cold, they move
to the bottom of lakes and ponds. There, frogs, turtles and many fish hide under
rocks, logs or fallen leaves. They may even bury themselves in the mud. They become
dormant. Cold water holds more oxygen than warm water, and the frogs and turtles can
breath by absorbing it through their skin.
Insects look for winter shelter in holes in the ground, under the bark of trees, deep
inside rotting logs or in any small crack they can find. One of the most interesting
places is in a gall. A gall is a swelling on a plant. It is caused by certain insects,
fungi or bacteria. They make a chemical that affects the plant's growth in
a small area, forming a lump. The gall becomes its maker's home and food source.
Every type of insect has its own life
cycle, which is the way it grows and changes. Different insects spend
the winter in different stages of their lives. Many insects spend the
winter dormant, or in "diapause." Diapause is like hibernation. It is a
time when growth and development stop. The insect's heartbeat,
breathing and temperature drop. Some insects spend the winter as
worm-like larvae. Others spend the winter as pupae. (This is a time
when insects change from one form to another.) Other insects die after
laying eggs in the fall. The eggs hatch into new insects in the spring
and everything begins all over again.

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I CAN READ


HOW DO ANIMALS SPEND THE WINTER?




Winter is cold. There is snow on the ground. People live in warm houses. What do animals do?
Some animals sleep all winter. It is a very deep sleep called hibernation. They
need little or no food. Bears and chipmunks hibernate. So do frogs, snakes and
even some bugs.
Other animals stay active in winter. It is hard for them to find food. They may
live in holes in trees or under the ground to stay warm. Deer, squirrels and rabbits
stay active.
Some birds fly south for the winter. We call this migration. They go to a warmer
place to find food. Other birds stay here all winter. We can help by feeding them.

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LEARN MORE ABOUT: HIBERNATION



The biggest problem for most animals in the winter is finding enough food. If an
animal's main source of food is very scarce in the winter, like insects or green
plants, it may solve this problem by hibernating. This deep sleep allows them to
conserve energy, and survive the winter with little or no food.
Most hibernators prepare in some way for
the winter. Some store food in their burrows or dens, to eat when they
awake for short periods. Many eat extra food in the fall while it is
plentiful. It is stored as body fat to be used later for energy.
Hibernators have two kinds of fat: regular white fat and a special
brown fat. The brown fat forms patches near the animal's brain, heart
and lungs. It sends a quick burst of energy to warm these organs first
when it is time to wake up. True hibernators go into such a deep
sleep that they are difficult to wake and may appear dead. Their body
temperature drops and breathing and heart beat slow down significantly.
For example, a hibernating woodchuck's heart rate slows from 80 to 4
beats per minute, and its temperature drops from 98 F to as low as 38
F. If its temperature falls too low, it will awaken slightly and shiver
to warm up a bit. If an animal lives in an area where the winter is
mild, it may hibernate only briefly, or not at all. However, even when
the weather is severe, hibernators may wake up for short periods every
few weeks to use their "toilet rooms" and eat if food is available.
Other true hibernators include the jumping mouse, little brown bat, the
eastern chipmunk, and some species of ground squirrels. There is even a
bird that appears to be a true hibernator. Called the gray and white
poorwill, it is related to the whippoorwill and lives in the mountains
of Colorado. Other hibernating animals do not experience major changes in temperature, heart rate
and breathing. Animals such as skunks, raccoons and some chipmunks are the light
sleepers, easily awakened. They may sleep during the most severe weather and wake
to roam and eat during milder weather.
The largest hibernators are the bears.
Although a grizzly or black bear's heart rate may drop from a normal of
40-50 beats per minute down to 8-12, its temperature drops only
slightly, allowing it to wake up quickly. These bears are also unique
because, unlike other hibernators, they do not eat, drink, or excrete
at all while hibernating, which can be as long as six months.
How do animals know it is time to
hibernate? This is still a subject of research. Hibernating animals
have something in their blood called HIT, or Hibernation Inducement
Trigger. Recent research suggests that it is some kind of opiate,
chemically related to morphine. As the days get shorter, the
temperature changes, and food becomes scarce, HIT triggers hibernation.
How and why it happens are still a mystery. There are other animals that
hibernate, or become dormant, daily. Many tiny warm-blooded animals
have huge energy requirements. It is difficult for some of them to
consume enough food to maintain themselves. To conserve energy, animals
like hummingbirds and little brown bats become dormant for part of each
day. Just as there are places where food
and water are scarce in the winter, there are other places where these
resources are scarce in the summer. To survive, some animals aestivate
('es-ti-vat), which is comparable to hibernate. While the northern
ground squirrels spend the summer eating and preparing for winter
hibernation, ground squirrels living in the southwest desert may avoid
the extreme heat by aestivating in their burrows.

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PROJECTS TO DO TOGETHER



NOTE: Please read all instructions completely before starting. Observe all safety
precautions. Parents supervise use of knives, scissors and needles.

PROJECT 1 - Feed and observe winter birds and animals


What you need:
Some or all of the following: popcorn, peanuts in shells, apples, cranberries,
pears, oranges, kiwi, peanut butter, suet (from butcher)
String, needle and strong thread, scissors, knife
Pine cone (to use with peanut butter), onion bag (to use with suet)

What to do:
(1) String the popcorn and cranberries on a long, doubled piece of thread.
String the whole peanuts on another thread.
(2) Slice the fruit crosswise, about 1/4-1/2 inch thick. Poke a hole about 2/3 of
the way across each slice, thread a 12 inch piece of string through it and tie the
ends together.
(3) Put peanut butter or suet into the holes in a pine cone. Tie a string to it.
(4) Cut suet into large pieces and put it into an onion bag.
(5) Hang the food from trees and bushes in sheltered areas, where you can see it.
Be patient. It takes time for birds and animals to find the food. Try different
locations. Note:
If you choose to begin feeding the birds regularly, try to do it throughout the winter.
They start to depend on you and may have trouble finding other sources of food later
in the winter.

PROJECT 2 - Feed and observe winter birds


What you need:
An empty plastic milk or water bottle, or a milk carton
Scissors, string, bird seed

What to do:
(1) Wash
the bottle or carton and rinse it well. Cut several small (2-3") holes
in the sides, about 2" from the bottom. Cut or poke two small holes
near the top and thread a long piece of string through them.
(2) Fill the bird feeder with seeds and hang from a tree or shrub. Scattering some
seeds on the ground can help the birds find the feeder. Watch the birds. Be patient.
Try different types of seeds and different locations. Record your observations.

PROJECT 3 - Discover how insects and spiders survive the winter


You Need:
Warm clothes and a nice day
flashlight, magnifying glass (helpful but not necessary)
large glass jar or milk carton, potting soil, cheesecloth or old nylon stocking
rubber band, knife or pruning shears.

What to do:

(1) Go outside. Look into crevices in bark, in and under dead logs, piles
of leaves, clumps of grass, shingles, around windows, in cracks between bricks, in
attics, basements, garages, and any place that provides shelter. Use your flashlight
and a stick for probing. Can you find active and hibernating adult insects, eggs,
and cocoons? Try to leave things as you found them.
(2) Try to find a gall on a tree or shrub. Collect several different types. While
still outside, cut them in half and observe what is inside.
(3) You can keep galls to see what emerges in the Spring. Cut a 4-6" section of
a twig with a gall. Put a layer of potting soil into a jar, or a milk carton with
holes cut in two sides. Put one end of the twigs into the dirt. Cover the jar with
cheesecloth or stocking secured by a rubber band, or slide the milk carton into a stocking
and tie the ends. Moisten the dirt occasionally. Keep the galls outdoors, out of
direct sunlight.

PROJECT 4 - Study animal tracks


What you need:
Animal tracks in snow or mud
animal footprints shown above.

What you do:

(1) Study tracks in the snow or mud and try to match them to the drawings.
(Sizes listed are approximate.) What animals were there? Are the tracks closely
spaced or far apart? Were the animals walking or running? How many different animal
tracks can you find? Keep a record over time.