Naturalist Corner: Adapting to Autumn's Rhythm

I’ve seen red and gray squirrels darting around, foraging for their winter stash of food, their movements frantic yet purposeful. It’s clear that the drop in daylight signals a shift in their behavior. It’s almost as if they understand that the window for preparing for winter is closing, and every moment matters. I can’t help but feel a bit of a kinship with them, as I too begin to prepare for the winter activities and holidays in the months ahead.

One of my favorite things to see this time of year is how the birds adjust. A few days ago, I was beginning a walk in DuMont Meadow when my ears perked up from the familiar sound of black-capped chickadees. Like squirrels, these small, energetic birds engage in food caching, a behavior where they hide seeds and insects in various spots to retrieve later during the winter. I watched a handful of chickadees dart among the staghorn sumac just one foot away. But what’s truly fascinating is the physiological change—one that I am envious of—that happens to help them with this task. 

As the chickadee gathers and stores seeds in hundreds of locations, its hippocampus—the brain region responsible for spatial navigation and memory in many vertebrates—expands by approximately 30 percent in volume through the creation of new neurons. By winter, their brains have literally rewired to help them survive the months ahead, a remarkable example of neuroplasticity in action. Simply put, they develop more brain power when they need to remember more things and then shrink it once the need is no longer there.

Even the black bears that roam this land are responding to the change in light. I think about them often as winter approaches, knowing they’re preparing for hibernation. As the days shorten, they stockpile calories, feeding heavily on acorns and berries, and prepare to rest through the cold months. It’s as though they know that decreasing daylight is nature’s signal to slow down, to enter a different state of being.

Changes in daylight have also triggered moose to enter their breeding season, also known as rut, for the past month. During rutting season, bulls travel far distances for potential mates and compete with other bulls. As the rut ends, moose return to eating and resting to prepare for winter. They start to move more cautiously, focusing on eating woody browse like willows, birch, and aspen, whose leaves and twigs provide much-needed sustenance in the colder months.

It’s also the time of year when the painted turtle begins brumation. Like hibernation in mammals, brumation is a physiological response to cold conditions that allows reptiles and amphibians to survive until warm weather returns. Painted turtles enter brumation at the bottom of lakes and ponds that they swim and sunbathe near during the warmer months.

While painted turtles are submerged, they can absorb some oxygen through their skin, mouth, and cloaca—a change from relying on their lungs during the warm months. Remarkably, they can brumate for months in environments with little to no oxygen, a feat most vertebrates cannot manage. Their drastically reduced metabolic rate conserves energy, allowing the turtles to endure without food or oxygen. While other animals, like bears, rely on fat reserves during hibernation, painted turtles use glycogen to generate energy, producing lactic acid in the process. To prevent lactic acid buildup, they adjust their blood chemistry and even store some acid in their skeleton and shell!

The trees, too, are responding to shorter days and cooler temperatures. The maples and oaks that have stood tall throughout the warmer months now enter a phase of dormancy, their branches bare against the sky. The reduction in daylight triggers this transformation, signaling to the trees that it's time to conserve energy and prepare for the harsh winter months ahead. With the loss of their leaves, trees reduce the amount of moisture they lose through transpiration, which helps them survive the cold and dry conditions. As I watch the last of the leaves fall, I can’t help but reflect on how the trees, too, embrace rest and renewal, much like the other creatures around me. The deep stillness of the forest at this time of year feels like the earth taking a collective breath, awaiting the return of the sun.