With December now upon us, our thoughts might well turn to cold weather. While southern Arizona is renowned, or even infamous, for its hot climate, contrary to popular belief we do indeed host winter as well.
The period from late December through January is normally the most frigid in our Sky Islands calendar. What do various species of wildlife do to keep their body temperatures at optimal levels when the mercury plummets? Failure to do so can easily translate to an unceremonious death. Even just a few hours of excessive cold can be fatal. As one might suspect, the solutions to this critical survival challenge seemingly run the gamut.
Perhaps one of the most straightforward ways for wildlife to keep warm is to passively bask in the sun. Even as bitter weather sets in, the sun often still shines, affording a calorically inexpensive way for some species to manage their internal temperatures. Greater roadrunners seek the warming rays of the early morning with a slick trick up their feathery sleeve. Rather than just sit on the ground or on a perch facing the sun, they instead turn their backs to it. Then this odd member of the Cuckoo family raises the plumes on its back, exposing both a layer of darker feathers as well as dark skin. An efficient solar panel revealed. A roadrunner may spend many minutes engaged in this behavior until it deems itself sufficiently warmed to go about its daily business.
The words “bird” and “hibernation” do not seem well suited to each other. While some mammals, such as chipmunks and certain species of bats, engage in this cold weather behavior, birds most assuredly do not. Right? Yes, but with one exception—the poorwill. When the mercury plummets, these cryptically colored birds simply find a nook where they perch on or near the ground. There, their body temperature markedly falls even as their respiration and heart rates precipitously drop. They stop eating or drinking, yet somehow manage to navigate through the worst that winter offers in this sort of suspended animation. The torpor can last for many hours or even weeks, though poorwills likely are active on warmer winter nights when moths—one of their dietary staples—are active. Some other birds, such as hummingbirds, other nightjars, and doves, can also enter torpor, albeit only overnight. This behavioral singularity in a bird world populated by some 10,000 species was recognized by the Hopi, who traditionally referred to the poorwill as hölchoko or “the sleeping one.”
Nature abounds with other ways wildlife adapt to or dodge the cold weather of winter. Ectotherms, such as our Sky Islands invertebrates and reptiles, often just wait it out, safely tucked into the ground, bark, wood, or some other natural medium. Their body temperature falls even as their housing provides some level of protection against the worst freezing conditions.
A few species even dare poke their heads out to sun themselves during our warmer winter days. Ornate tree lizards and some grasshoppers fall into this category. What about those aforementioned moths, who are part of the poorwill diet? Unlike most of their butterfly kin, they’ve evolved hefty bodies with dense hair, traits that help to keep them within optimal body temperatures on cooler nights. Being active primarily at dusk may also aid them in avoiding the coldest parts of darkness.
Ducks and other birds with oil glands avoiding undo wetness and hence, cold; ants with nests acting as solar panels; pronghorn and deer with hollow, insulative hairs; migration to warmer climes; tree squirrels with sleeping bag-like nests composed of warmth-retaining plant material; dense fur; a fat-rich diet; calorically streamlined behavior, relying upon cached food; seeking warm microclimates… The list of wildlife adaptations to cold is truly extensive. Think about what you would do if suddenly deprived of your own home and you’ll begin to fathom the biological imperative that all other species must adhere to in winter: keep warm!
Vincent Pinto and his wife, Claudia, run RAVENS-WAY WILD JOURNEYS LLC, their Nature Adventure & Conservation organization devoted to protecting and promoting the unique biodiversity of the Sky Islands region. RWWJ offers a wide variety of private, custom-made courses, birding & biodiversity tours. Visit: ravensnatureschool.org