Thursday, January 8, 2015

Do Critters Get Cold Too?

By John Windau, Wildlife Communications Specialist, District Two, Findlay

Whenever the bottom falls out of the thermometer and temperatures hover close to zero, or below, we at the Ohio Division of Wildlife start to receive quite a few calls from concerned people about the fate of their favorite wildlife species. So, what about our native wildlife that have been exposed to this weather? It may be surprising, but for the most part, they are just fine. It is easy to personify, or bestow human traits upon wildlife, particularly species we are fond of.  However, it is important to remember that native species of wildlife are well adapted to deal with winter conditions.  Although the past few years have been extreme, these adaptations have developed over thousands of years and thousands of  winters. These adaptations can be classified into two groups: structural or behavioral.
Structural adaptations are physical traits, handed down through genetics, that help an animal better survive in its environment. In the case of winter conditions, an obvious example for most mammal species is the pelage, or their covering of hair or fur. In fall, most mammals in Ohio replace their thinner summer coats with a dense winter coat.  This is why furbearer trapping seasons are scheduled for late fall and winter. These thick coats are comprised of two layers, an inner dense undercoat which traps air and provides warmth, and an outer layer of guard hairs to repel moisture, protect the undercoat, and provide camouflage.

Have you ever noticed that the northern members of a species seem to be a bit larger than their southern counterparts?  For example, a rabbit in Arizona is going to be much smaller than a rabbit in Ohio.  It has to do with how their bodies deal with heat. In the south where summers are very hot, bodies need to remove heat in order to protect vital organs, while in the north the opposite is required, heat needs to be retained during the cold months. So how does size help? Think of a cube. For every one additional increase of surface, the volume increases three fold. So the larger and stouter northerly animals have more mass relative to surface area to protect internal organs. Likewise, the thinner and lanky southerly versions often have larger surface areas, such as larger ears, in relation to their volumes to help dissipate heat.

Behavioral adaptations are ways an animal reacts to changes in its environment that help it better survive. Hibernation is a behavioral adaptation that is ingrained in some species. These species have no choice whether or not they hibernate. Hibernation is a prolonged state of inactivity with lower body temperature, slower breath and heart rate, and sometimes very low metabolic rate. In Ohio, groundhogs and bears are some of the few mammals that enter hibernation. Other species, like skunks and raccoons enter a lesser form of hibernation called torpor. Animals in a state of torpor are similar to those in hibernation, but for only a short amount of time, such a few hours or a few days. Often, these animals will “sleep” during periods of severe weather and emerge once the weather breaks. These two adaptations help an animal conserve energy.  Low metabolism and slowed bodily functions expend much less energy that they can save for when the weather clears up and can get out to look for food.

Some species learn adaptations from their parents.  Just like Eskimos, many species of wildlife, particularly game birds like ruffed grouse and pheasants, rely on snow for insulation and to protect them from the harsh winds. They will bury themselves in a snowdrift to shelter from the wind and cold.  But, when woodlots and fence rows are removed, the wind driven snow continues on rather than forming snowdrifts along the fences, leaving these species susceptible to the elements.  Similarly, some animals, like chipmunks and squirrels, learn to cache or store food for winter.  They will hide their supplies

Some species have adapted other ways to cope with unfavorable weather. Many species of birds choose to avoid the cold altogether and fly to areas where food is abundant. Migration is an adaptation to capitalize on the seasonally abundant food sources as they occur in different regions of the world.

Still, there are some native species, which are not very tolerant of Ohio’s weather patterns. Often, these species are better adapted to other regions of the country and the edges of their home ranges spill into Ohio. These species are called edge species, since they are not fully adapted to survive in the area. The Northern bobwhite quail is one example of an edge species in Ohio. The numbers of Northern bobwhites in Ohio are subject to dramatic fluctuations due to winter weather conditions. Their populations often increase during mild winters while prolonged snow cover and below normal temperatures may decimate quail populations. On the other hand, Ohio is at the southern edge of the snowshoe hare’s range. Ohio’s relatively “mild” winters mean that the species was probably never abundant here and historically snowshoe hares were likely confined to the Snow Belt region in the extreme northeast corner of Ohio.

In the end, every species has adapted unique ways to help them survive in their environment. For Ohio’s wildlife that includes winters just like the one we are experiencing this year. Although, to some these conditions may seem unbearable, most all of the native wildlife species are well adapted to these conditions. For more information about a particular species that interests you, visit the Species Guide Index at