Winter! Words and images that come to mind are snow falling, chilly temperatures, crisp air, hugging yourself to keep warm.
Winter is a time of bundling up with mittens, boots, and hats to play in the snow or enjoy the out-of-doors.
Winter is a time of year to snuggle down before a fireplace, drink hot chocolate, read a book, and listen to music.
But winter is also a time of year when young and old used to gather together to tell stories. It was a time when people questioned why the world worked the way it did. The ancient ones told stories to explain the mysteries of life, how fire came to be, how animals survive the cold, and how the world was created. Our electronic world has changed this time of community, of coming together to listen and have fun.
This next Saturday, 11:00 AM, at the Nature Center, storytellers Terry Foxx and Kimberly Gotches will bring back the ancient practice of storytelling during the winter. Using wisdom of the ancients and modern-day science, they will explain how fire came into the world and how animals survive the cold in a fun and interactive program for both children and adults.
So how does science explain how animals survive the winter?
How animals survive has been a curiosity since the beginning and still is one of those marvels of nature that challenges scientists. Scientists are finding more and more about the interesting and complex ways animals survive through periods of cold.
Today we understand there are three basic ways animals survive the winter: migration, adaptation, and hibernation. Although we can categorize three basic forms, the survival of any one animal is sometimes a complicated mixture. Let’s explain a little of the science behind these three survival mechanisms and look at examples.
Cranes over Bosque del Apache. Photo by Terry Foxx.
Migration
Migration is the movement of animals from one place to another. It can be a short distance to find a warmer niche or long distances to a warmer climate. Migration is stimulated by the changes in day length and temperature.
Some birds fly amazing distances. For example the artic tern nests near the north pole in the summer but in the autumn it flies all the way south to Antarctica, returning north in the spring. That is over 10,000 miles! Amazingly, they find their way to the same place each year. They seem to navigate using the sun moon and stars for direction and have an internal compass for using the Earth’s magnetic field.
A fun place to go in New Mexico is the Bosque del Apache near Socorro. Every year migrating Sandhill Cranes, Snow Geese, and other birds can be seen in the fields and ponds of the Wildlife Refuge. When you get up early in the morning, you can see thousands of birds waking up and flying off to their feeding grounds. It is a breathtaking experience. On their way to and from the Bosque, the Sandhill Cranes fly along the Rio Grande and White Rock Canyon. You can hear them calling as they fly over White Rock.
A fascinating way to record your observations about when birds appear in the spring and leave in the fall is to join the Nature Center’s on-line birders group (www.peecnature.org, press on the header “Learn.” From the pull down menu go Interest Groups and sign-up.). Someone has already heard cranes heading north—and it is February (we still think it is winter)! Other birds are of particular interest in their coming and going. Nature Center birders anxiously await the first hummingbird signaling summer.
When we think of migration we often think of birds, but other animals also migrate, sometimes not long distances. For example an earthworm can move farther down into the soil below the frost line to survive freezing. They have been found six feet beneath the soil surface (for an earthworm that probably is a really long way!). When the soil warms, they move back up toward the surface.
Insects also migrate. Most well-known is the migration of the Monarch Butterfly. Butterflies can migrate 2500 miles! Those butterflies that live in the East migrate to Mexico and hibernate in oxyamel fir trees. If the butterfly lives west of the Rockies, it heads for Southern California. Monarch butterflies are very important pollinators and are disappearing because of urbanization and agricultural practices. A fun citizen science project is to track the path of the Monarchs.
The Nature Center has an interest group called “Butterfly Watchers.” Sign up on the website www.peecnature.org and follow the directions above. You will learn about different butterflies and you can report when you see a Monarch.
Adaptation
Adaptation is another way animals survive the winter. To keep warm some animals grow a thicker coat of fur. Examples include coyote, big horn sheep and deer. In some animals, the hairs are hollow, making them more insulating.
As a protective mechanism from predators, the new fur may be white to hide them in the snow. Examples are the Snowshoe Rabbit and Arctic Fox. Other animals gather extra food in the fall and store it. Animals like the fox may eat berries in the summer and small mammals in the winter, changing their food source. Rabbits and deer spend winter looking for moss, twigs, bark. and leaves to eat.
A variety of animals find winter shelter in holes in trees or logs, under rocks or leaves, or underground. These shelters are warmer and animals like mice, raccoons, and squirrels huddle together to stay warm.
Hibernation
Hibernation is a complex and fascinating process. Heart rates drop sometimes as low as 4 four beats per minute and respiration drops to one breath every three to four minutes! Scientists distinguish between true hibernators and those who use torpidity as a mechanism. Regardless, many animals sleep for extended periods of time and spend a lot of time in the late summer and autumn finding food to increase their fat stores within their bodies. True hibernators don’t wake up until spring regardless of the stimuli. Examples of hibernators are chipmunks, ground squirrels, bats, and some mice. They have enough fat reserves to carry them through the winter.
Animals like raccoons and tree squirrels use torpidity to help them survive. Torpidity is a reduction of the metabolism which allows for lower body temperature and oxygen consumption. 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. These animals can sleep for weeks at a time and then wake up to eat and defecate. During their wake time they seek out their hidden caches of food collected during the summer and fall.
So what about bears? Are they true hibernators or not? Scientist disagree with terminology. But one thing is for sure, don’t disturb a bear in his sleepy state because he can wake up in an instant, attack, and then go right back to sleep!
We have mostly talked about warm-blooded animals, but cold-blooded animals such as frogs, snakes, and lizards must also survive through winter. They lack internal control over their metabolism. They depend on the warmth of the sun to keep them active. In the winter they would freeze if they did not seek shelter and undergo chemical changes to prevent freezing. They can burrow into the mud or congregate in small caves. Rattlesnakes, for example, congregate in rock crevices to hibernate for the winter. Those spots are known as “snake dens” and they are used every year.
If you want to learn more about how animals survive the winter, here are some books you can find in Mesa Public Library. Some are entertaining stories and others are informative non-fiction.
Hibernation by Anita Ganeri
The Mitten by Jan Brett
Bear Snores On by Karma Wilson
Time to Sleep by Denise Fleming
Animals Hibernating by Pamela Hickman
Do Not Disturb: The Mysteries of Animal Hibernation and Sleep by Margery Facklam