For many people, the transition from fall to winter is characterized by gift-giving, decorations, warm jackets and cozy sweaters, not to mention cookies, pies, and other sweets. However, from a naturalist’s perspective, winter is perhaps best characterized by change: change in weather, foliage, animal behavior, and more. By observing the natural world, we notice both overt and subtle clues that signal seasonal change. The study of how the biological world responds to the changing of the seasons is called phenology.
In the Greater Yellowstone Ecosystem (GYE), the phenological clues that suggest winter is approaching are numerous. Aside from obvious indications such as yellowing leaves, dropping temperatures, and snow accumulation, the return of elk to the National Elk Refuge (NER) and the return of bighorn sheep to Miller Butte are major indicators that winter is soon to arrive in Jackson. Like many herd mammals that inhabit the GYE, elk and bighorn sheep migrate to lower elevations in search of more easily accessible food to help them survive the harsh winter. For school groups and Teton Science Schools’ participants, driving along the base of Miller Butte to study bighorn sheep behavior or taking a sleigh ride on the NER yield exciting close encounters with these large ruminants.
In addition to the clues that sheep and elk give us, there are many other animals in the GYE to watch for phenological signals of winter’s arrival. For a patient and observant naturalist, a rare glimpse of an ermine—also known as a long-tailed weasel—can be a tell-tale sign that winter is arriving in the GYE. Ermine change the color of their furry coats from rusty brown and light yellow in the summer to white just before the cold, snowy months set in. This camouflages the mustelid as it hunts for rodents in the snowpack throughout the winter.
By taking note of the clues found in nature that point to change—by studying the phenological events of our local ecosystems—we become attuned to the patterns and cycles that surround us. Additionally, and perhaps most importantly, we create and strengthen long-lasting, meaningful connections with the natural world, something we should all be encouraged to do more often.