A Delicate Balance

Seasons are changing. Shorter days, chillier nights, and peaks dusted in new snow all inform us winter is approaching. But as we don our warm jackets and boots to enter this seasonal wonderland, what are the critters in the Foothills doing? Hibernating? Brumating? Sleeping? It depends.

Bears eat as much as they can during the autumn before retreating to their dens to hibernate. During this long winter nap, endothermic (warm-blooded) animals’ metabolism decreases significantly to conserve energy. Their heart rates, breathing, and even brain activity slow down dramatically, and they rely on stored fat to produce the heat essential to survival.

By contrast, ectothermic (cold-blooded) reptiles and amphibians brumate. Dropping temperatures trigger their metabolisms to slow down. They stop eating and seek deep spaces—such as burrows in the soil, spaces under rocks, and tree stumps—to find protection from frigid surface temperatures. Though awake, these critters are lethargic; all metabolic processes, including body temperature and heart and respiratory rate, remain very low. Some snakes, including rattlesnakes, winter together huddled in ‘hibernacula’ to share collective warmth.

Then there are the animals that stay active all winter, such as elk. As cold arrives, elks’ summer fur transitions into a thick double coat. Long, hollow guard hairs provide waterproofing over very dense undercoats. This parka keeps heat close and prevents snow from melting on their backs. During cold, overcast days and at night, elk bed down on protective east- and north-facing slopes, beneath dense stands of trees that offer shelter from snow and wind. With their legs tucked underneath them and their guard hair held up, they huddle bundled in warmth. On sunny days, elk move to open west- and south-facing slopes, where they warm themselves in the sun. Elk must eat to produce heat. While they prefer noshing on dry grass, as winter progresses, they resort to bark and other less desirable choices to make it through the lean months.

Foothill fauna are well adapted to extreme temperature fluctuations, but they are vulnerable when disrupted. A disturbed bear wastes essential fuel, a lethargic snake cannot relocate, and elk need hushed corridors between forest shelters and sunny slopes. As we recreate this winter, let’s remember we are but visitors in a wintry quiet zone. As we engage in our beloved winter activities, we mustn’t tip the balance for the animals that call the Foothills home.

By Hilary Jacobs