The air conditioner in the roof of my son’s guest house (read travel trailer) hums and pulses as it goes about the job of squeezing the excess moisture out of air that, without the help of this mechanical marvel, feels like a steam room. At the same time, it is maintaining the temperature in the room in which I’m writing this column at a comfortable 72 degrees.
Here in central Virginia, a stalled cold front, apparently not satisfied with the torrential downpours it produced upon its arrival a few days ago, has been providing continuous fog, mist, drizzle or steady rain. Take your pick. But, this morning the sun came blazing out and the result is equal numbers – 82 degrees and 82% relative humidity. Steamy, muggy, miserable.
Of course, we humans may be the only organisms around here worrying about the way it feels. Oh, my son’s border collies have their tongues hanging out and are staying in the shade, but their eyes are bright and they don’t seem the least discouraged by the heat, especially since they know my pocket may hold a dog biscuit or two.
Human beings are really pretty puny. Naked, we are only comfortable at air temperatures between 75 and 85 degrees. Exposed to too much sun, our featherless, mostly hairless and furless bodies soon burn and blister. Our food must be untainted or we become sick unto death, although we eat almost anything - especially if it isn’t good for us. We can’t, with impunity, lap water from the local stream without exposing our bodies to a host of pathogenic bacteria and parasites. How come Rocky and Rex can guzzle any water they encounter to wash down their delicious snack of thoroughly ripe road-killed racoon and still maintain their health?
During the last few days my family and I have mostly retreated indoors or limited our travel to rubber-tired environmental chambers (cars) where we could control the temperature and humidity to our liking and stay dry.
Birds, on the other hand, sat in the rain with comfortably dry skin, their overlapping, waterproof, shingle-like feathers completely shedding the downpours of precipitation. Many small mammals retreated to burrows, but deer and other large critters, such as cows and horses, just calmly went about their business of grazing. Their higher body temperatures (about 101-102 degrees or higher) kept them from chilling and an occasional shake flung off excess moisture. This time of the year in Virginia, as elsewhere, mammals are shedding their thick undercoat of fine, insulating fur that carried them in comfort through the winter. Your cat or dog has probably been shedding like mad for some time.
Many other adaptations are found in the animal kingdom. Beaks - short and stout for seed crushing, long and pointed for insect snatching or wood pecking, help birds function in their appointed place in nature. Teeth – flat and solid for grass and leaf munching, sharp and tapering for flesh tearing, enable mammals to live successfully in their given environment. Bird feet, modified with a tendon that automatically clenches their toes when they sit on a branch, allow perching birds to sleep without falling out of trees. Talons and claws uniquely arm hawks and predatory mammals. Hawks and eagles have telescopic vision enabling them to recognize food from high in the air. Owls eyes are hypersensitive to low light and their wings are fringed with delicate special feathers allowing them to swoop silently on unsuspecting mouse meals in the dead of night.
Rain or shine, the Virginia birds awoke each dawn, singing at full volume – to me a pleasing introduction to the day. They, however, were not engaged merely in an aesthetic musical exercise. Their calls and songs were intended for more utilitarian uses such as attracting a mate, warning trespassers away from their territory or identifying their family members.
Plants and animals live where conditions for each are ideal. Some plants cannot tolerate full sun, so they only occur in shaded forest areas. Some would shrivel and die with even a hint of dryness, so they grow submerged in ponds and lakes. Intermediate types thrive in bogs and swamps. The variations are endless. Some plants, like the Magnolia, have thick, waxy surfaces to retard moisture loss. Others have fuzzy leaves that accomplish the same thing by maintaining high humidity at the leaf surface. Thorns, stinging hair and unpleasant taste are adaptations to discourage browsing animals from devouring certain plants. A few toxic plants kill those bold or unwise enough to partake.
Although populations of plants and animals rise and fall, sometimes catastrophically, in general they exist in a fairly stable and supportive relationship. Scientists can actually determine how many animals can maintain themselves healthily in a given area, based upon available food, water, shelter, competition for mates, etc. They call that limit “carrying capacity” and it is sometimes graphically demonstrated in overgrazed areas by a line of completely cleared leaves and tender branches as high as the animals can reach in shrubs and trees.
In contrast to humans, other members of the plant and animal kingdoms largely adapt to the environment in which live, rather than build elaborate systems to adapt the environment to themselves. Oh, nests and burrows help, but they don’t manufacture clothing in endless varieties or construct complicated, hi-tech homes to allow themselves to moderate or change conditions. However, in ways truly marvelous and diverse, we all – wild animals, humans and plants – manage to live pretty well in the fields and forests we call home.
Dr. Risk is a professor emeritus in the College of Forestry and Agriculture at Stephen F. Austin State University in Nacogdoches, Texas. Content © Paul H. Risk, Ph.D. All rights reserved, except where otherwise noted. Click firstname.lastname@example.org to send questions, comments, or request permission for use.