What cues do you use to know when seasons change?”


By Kirsten Carlson
Using only your sense of touch/feel, how would you know when one season ends and another begins? Perhaps you feel a change in temperature? Colder in the mornings than normal but still warm during the day? Maybe you feel a cold rain and wind? Add another sense such as sight (a little ambiguous as different organisms see light and dark in very different ways). Do you think you could hear when seasons transition? Rachel Carson believed so as written in her book, “Silent Spring. “

What cues do you use to know when seasons change?

Autumn is upon us. How do organisms “know” to prepare for the oncoming winter? What sensual cues do you think they respond to as guides to prepare for winter? Isn’t that what autumn is all about — preparation for winter? Go outside and observe the behaviors of organisms this time of year. What’s happening? Leaves change color and may fall to the ground. What tells a plant to do that? Some fruits and nuts ripen. Squirrels and blue jays gather acorns and other nuts to bury in the ground only to find again when winter hunger sets in. How do they remember where they placed all those acorns and nuts? Many birds and some insects, such as the monarch butterfly, migrate south to overwinter in climates that meet their winter habitat needs. Some mammals grow a winter coat before winter even sets in. Worms burrow deeper down in the soil. What do our native reptiles do?

How do they all know to perform such behaviors? They use nature’s cue cards. And basically, it all comes down to an organism’s chemistry. You are already probably familiar with this concept. If you experience continued sun exposure, specific cells in your skin receive those sunlight wavelength signals and respond by making a chemical to protect your skin cells from damage. The result, a tan.

The same idea occurs in organisms who cells respond to the various signals from amount of daylight/darkness in a 24-hour period, difference between the daily low and high temperatures, angle of the sun, orientation of star patterns, changes in weather conditions, and soil temperature, just to name a few. Organisms luckily do not use just one cue, but a few so that they can respond appropriately and without haste.

For the blue jay and the squirrel to know to hide their food and then to find it again requires environmental cues to alter their brain chemistry to help them remember where their food is stashed. These same cues cause the hair of some mammals to grow a thicker coat, and for ant and monarch butterfly to have their “blood” chemistry change to something similar to anti-freeze. These cues also tell the turtle to burrow down in the lake or pond, slow their breathing and “sleep” until they receive signals to emerge in the spring. And these cues also cause the leaves of trees to breakdown chlorophyll (the green pigment), store as many other compounds in their roots, and to drop or modify their leaves.

There are many more examples. You can research some on your own to help you understand how organisms are adapted to respond to seasonal changes. You are sure to be amazed.

If you are interested in finding the nature that resides in you and to find the extraordinary in the ordinary things we see or pass up every day, then consider participating in one or more of our events, where you can get personal with nature to make or strengthen your connections to Earth. Find an event at oakheritageconservancy.org/events/

Kirsten Carlson is a biology teacher at Ivy Tech Community College and the Education and Outreach Coordinator for Oak Heritage Conservancy. Oak Heritage is a nonprofit that protects over 1,100 acres of habitat in southeast Indiana, including old growth forests, native wildflower meadows, creeks, and wetlands. They host hands-on nature programs for the public. Their work is possible because of support from their members, donations, and grants.

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