And so it begins. A curious look out your window won’t reward you with pops of purple and blue flowers in the fields. However, you may catch glimpses of yellow from a falling leaf and find yourself wishing for a hot cup of cocoa and an extra layer of clothing.

If you’ve had the pleasure of spending a fall in Colorado, you may be familiar with the famous changing color of the aspen trees. From green to gold, this popular foliage marks a time of year that brings in visitors from all over to experience the yearly shift from summer to fall. So as we welcome the coming months and the shift into early October with the rising excitement of Halloween in the air, we may also find ourselves curious as to how & why these changes occur. But to truly understand the depth of this beautiful change, it’s best to return to the basics.

Throughout the year, our planet is continually rotating around its axis. The shift we experience from warm summer nights to brisk fall mornings can be attributed to the Earth’s tilt toward the sun. As we rotate on our axis, the pole of the Earth tilted towards the sun will experience warmer temperatures, or summer. At the peak of our summer, the northern hemisphere is situated in a more direct path of the sun's energy. What this means is less sunlight gets scattered before reaching the ground because it has less distance to travel through the atmosphere. As the Earth continues to revolve around the sun, that pole is moved so that it is pointing away from the sun, reducing the amount of direct sunlight that will be hitting us. This brings us around to fall (when the Earth’s poles are tilted sideways with respect to the sun), and eventually, winter. At the height of fall, or the autumnal equinox, the sun is directly above the equator, resulting in approximately equal times of daylight and night. This results in the gradual decrease in temperature… and the inevitable increase in eagerness from our beloved winter recreation enthusiasts.

But as we sort through our closets and prepare for fall, pulling out beanies and ski jackets, it’s worth noting that not all species have the luxury of a seasonal wardrobe change. As temperatures begin lowering, a certain biological clock in wildlife ticks along the important passing of time, as well. Most animals have evolved towards two major options for winter preparation: adaptation or migration. In the case of some of our feathered friends, like the hummingbird, migrating south towards warmer regions has become the destination of choice. On the other hand, certain mammals like the weasel are able to perform a bit of a costume change in preparation for the colder months ahead. Just like hibernators that know when it’s time to store up fat for a long winter, animals that switch colors have an internal clock that regulates the timing of their change, allowing them to know just when and how to adapt to colder temperatures. Whether it’s booking a ticket south, sizing up the new winter fur, or gathering a feast of a lifetime, wildlife have learned to change with the seasons and embrace them in all their force.

So, when you find yourself enjoying the outdoors this season, take a moment to experience fall from the perspective of others: the frantic flow of a squirrel searching for food, or the slow and steady stumble of a black bear gearing up for rest. Each season brings with it its own particular brand of beauty. And if you’re unsure of where to start, considering joining along for a Naturalist Guided Walk — 2pm at our Avon Campus Monday through Saturday — because nothing beats sharing the seasons together.

Bridget Whyte is a Naturalist for Walking Mountains Science Center. As a young explorer, she enjoyed the thrills of raked leaf piles at the end of the driveway; now she finds excitement in the breakdown of chlorophyll and chemical changes that result in the beauty of fall foliage. You could say her love for autumn has never fall-tered.

Photo by Rick Spitzer