While the weather outside may indeed get frightful this winter, a parka, knit hat, wool socks, insulated boots and maybe a roaring fire make things bearable for people who live in cold climates. But what about all the wildlife out there? Won't they be freezing?
Anyone who's walked their dog when temperatures are frigid knows that canines will shiver and favor a cold paw — which partly explains the boom in the pet clothing industry. But chipmunks and cardinals don't get fashionable coats or booties.
In fact, wildlife can succumb to frostbite and hypothermia, just like people and pets. In the northern United States, the unfurred tails of opossums are a common casualty of cold exposure. Every so often an unusual cold snap in Florida results in iguanas falling from trees and manatees dying from cold stress.
Avoiding the cold is important for preserving life or limb (or, in the opossum's case, tail) and the opportunity to reproduce. These biological imperatives mean that wildlife must be able to feel cold, in order to try to avoid the damaging effects of its extremes. Animal species have their own equivalent to what human beings experience as that unpleasant biting mixed with pins-and-needles sensation that urges us to warm up soon or suffer the consequences. In fact, the nervous system mechanisms for sensing a range of temperatures are pretty much the same among all vertebrates.
One winter challenge for warm-blooded animals, or endotherms, as they're scientifically known, is to maintain their internal body temperature in cold conditions. Interestingly though, temperature-sensing thresholds can vary depending on physiology. For instance, a cold-blooded — that is, ectothermic — frog will sense cold starting at a lower temperature compared to a mouse. Recent research shows that hibernating mammals, like the thirteen-lined ground squirrel, don't sense the cold until lower temperatures than endotherms that don't hibernate.
So animals know when it's cold, just at varying temperatures. When the mercury plummets, are wildlife suffering or just going with the icy flow?