Oak trees add the brilliance of their turning leaves to fall’s burst of colors. The oaks’ acorn crop is also important winter food for several forest creatures. Chestnuts once supplied winter food, too, but a blight virtually eliminated the chestnut trees earlier this century, adding to the importance of acorns.
Bears, Boars and Acorns
As frosts touch the earth and the reds and yellows of fall creep down the mountainsides, oaks, hickories, beeches, and other trees shed their fruits. Many animals will join in the harvest of this fruit, but several, especially bear, deer, wild boar, gray squirrel, chipmunk, turkey, and ruffed grouse, are particularly dependent on this mast, as it is called, for their autumn and winter welfare. With the chestnut gone these animals must rely mostly on acorns. Oaks, unlike the chestnut, do not produce consistently, but fruit abundantly some years and fail in others. In the poor years, when competition for mast is keen, the effects are starvation, wandering, and mass migrations. The appearance and multiplication of European wild boars in the park have only added to the pressure on the native animal species. Acorn shortages bring into sharp focus the life styles and survival systems of the mast-dependent animals. From among these the wild boar emerges as an ecological villain, although we should perhaps cast man, who introduced the boar here, in that role.
The loss of the chestnut illustrates how a change in one element can irrevocably alter an entire ecosystem. As the chestnuts of the Smokies died, their place was taken primarily by chestnut oak, northern red oak, red maple, hemlock, and silverbell. The annual mast crop suffered from this change in two ways. First, only about half of the replacement trees were mast-bearing oaks. Second, oaks are not dependable mast-bearers. Mast failures seem to result mainly from spring freezes during the pollinating and fertilization of oak flowers. Chestnuts bloomed in the first two weeks of June when the danger of frost was slight and so they bore well nearly every year. This difference in flowering time has had reverberations throughout the animal world within these mountains. By looking into the life histories and population dynamics of some of the acorn eaters we may get some idea of the nature and extent of those reverberations.
Whitetail deer prefer young forests and mixtures of forest and field because in these areas an abundance of shrubs and herbaceous plants provides ample food. The mature forests of the Smokies have relatively little forage near the ground and so they support only small numbers of deer. In the Cades Cove area, however, the lush meadows and second-growth forest feed several hundred deer. In the fall deer join in the mast harvest, but they do not depend on it as do the bears, gray squirrels, wild boars, and chipmunks. Deer have the option of eating twigs, buds, and herbaceous plants. They eat acorns, however, and this nutritious food will help them enter winter in good condition. Deer mating takes place from September to November in the Smokies, as the mature males each run with a female for several days, then hunt for another. In winter the bucks shed their antlers and join the does and yearlings. In May or June the does give birth to their spotted fawns, usually twins. The summer bands you see in Cades Cove are again separated by sex as the bucks once again grow antlers in preparation for the autumn battles.
Now that wolves and other large predators are gone from the Smokies, starvation and disease are the principal checks on deer numbers. Late in 1971 a disease that causes massive bleeding struck the herd in Cades Cove, killing many of the deer and a few cattle. But by the following spring an increase in the production of offspring and the influx of deer from nearby areas brought the herd back almost to its former number.
Gray squirrel numbers fluctuate even more dramatically, as populations build up and then collapse, but these oscillations occur even when food is adequate. Until recently, some observers thought these oscillations were amplified by mast failures, but apparently they are not. In the Smokies, gray squirrels are found mostly in the oak and beech forest of the lower and middle elevations, while their smaller cousins, the red squirrels, stick more to the upper elevations. In years of extreme low population swings such as 1946 and 1968, many migrating squirrels have been killed on the highways; others have even been seen attempting to swim Fontana Lake. The loss of gray squirrels in 1946 was estimated at 90 percent for some watersheds.
Turkeys and ruffed grouse both feed heavily on acorns in the fall, although they, like the deer, have other possibilities. Turkey and grouse also feed on the fruits of dogwood and wild grape; beechnuts in good years; seeds; and buds. A statewide study in Virginia found that acorns supplied about one-quarter of the annual diet of wild turkeys, and this proportion is much higher in fall. Acorns are also a top food item in fall for ruffed grouse.
We come now to the two chief antagonists in the annual mast hunt, bears and wild boars. The arrival of wild boars in the park has meant added competition for bears, as well as many other disruptive ecological effects. By considering the population dynamics and seasonal activities of these two species, we get a clear contrast between their roles. One fits in with the forest “establishment” and one clearly does not.
How many bears live in the park? This is difficult to determine because bears are secretive and tend to wander. The National Park Service estimates that numbers usually range from about 400 up to about 600, depending on reproduction, food availability, extent of poaching, and other factors. The estimates are based on intensive research by the University of Tennessee in the northwest quarter of the park.