The Role of Animals in Natural Communities

Natural communities are named after plants, but animals play a crucial role in maintaining the health of natural communities. Plants and animals need each other in order to survive and thrive.
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How Animals Need Plants

Food to Eat

Leaves and tender twigs are a major component of the diet of many insects, as well as larger animals such as deer and rabbits. Seeds are an important food source for many animals. Wildlife managers call edible seeds “mast.” Seeds encased in a dry, hard shell—such as acorns—are hard mast. Seeds surrounded by pulpy flesh and thin skin—such as berries—are soft mast.

Soft Mast: Eat While the Eatin’ is Good

High-fat berries of northern spicebush (Lindera benzoin) are good fuel for birds migrating south in autumn.
Photographer: Gary Fleming

Berries and other soft mast don’t last long and are eaten by wildlife as they ripen. Soft mast is a good source of vitamins, carbohydrates, and moisture. Producers of soft mast include flowering dogwood (a favorite of many birds and mammals), blackgum, blueberry, huckleberry, serviceberry, cherry, wild grape, poison-ivy, and viburnum.

Hard Mast: Long Shelf Life

The hard covering of hard mast such as acorns and beechnuts protects the seed from drying out and allows it to last for a long time without decomposing, making it an important winter food.

Acorns, a high-energy food source, are the most important wildlife food in the deciduous forests of North America.1 White-tailed deer, white-footed mice, squirrels, eastern chipmunks, raccoons, red foxes, woodpeckers, blue jays, crows, white-breasted nuthatches, wood ducks, and mallards all eat acorns.

High-fat American beechnuts are another abundant and significant food source for many forest animals. Other hard mast producers include hickories and American hornbeam. The food supply from hard mast sources varies significantly from year to year. Ecobit: Hard Mast—Feast or Famine

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A Place to Live

A juvenile barred owl sits by the nesting cavity its parents selected in an old hollowed out tuliptree.
Photographer: Julie McCall

Plants also provide wildlife with shelter, nesting sites, and protection from predators. Squirrels and some birds of prey build nests in forks of tall trees. Other birds build nests in bushes and small trees.

Nesting in Cozy Cavities

Many woodland creatures use tree cavities or hollows for nests, including squirrels, raccoons, owls, American kestrels, wood ducks, wrens, Carolina chickadees, tufted titmice, white-breasted nuthatches, great crested flycatchers, and several species of woodpeckers and bats. Cavity nesters make use of trees such as blackgum, American beech, American sycamore, ash, maples, and American basswood that tend to readily form natural cavities or hollows as a result of wounds from broken branches, fire, decay, or other damage.2  3

In trees where cavities don’t naturally exist, some animals—primarily woodpeckers—are able to excavate cavities in which to nest. Secondary cavity nesters, such as wrens and tufted titmice, take advantage of existing cavities, whether naturally present or excavated by primary cavity nesters.

Streamside Trees

Deciduous trees overhanging streams and ponds keep water temperatures cool in summer for fish and other water-dwellers, and also supply organic material (detritus) to the water. This provides food for invertebrate animals such as aquatic insects—important not only to fish but the entire food chain.

Dead Trees Teem with Life

Dead standing trees and fallen trees on the forest floor serve as nesting, observing, and resting sites for reptiles, amphibians, small mammals and birds. Dead trees also attract insects, mosses, lichen, and fungi, which in turn feed many birds and other wildlife.

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How Plants Need Animals

Animals help plants reproduce by carrying pollen from plant-to-plant and by spreading seeds. Animals that eat insects and small mammals help reduce damage by caterpillars, rabbits, and other plant-eaters.

Birds, Bees, Sowing Seeds

Hummingbirds, bees, butterflies, other insects, and even bats pollinate the flowers of plants. Pollination brings together pollen from male and female plants, which allows plants to produce seeds.

Many seeds are encased in tasty packages that animals eat. When birds eat berries and fruit, any seeds in the fleshy pulp that survive the bird’s digestive tract get spread throughout the forest. In some cases, the benefit to the seed is more than the distance gained from the parent plant. For example, the fatty pulp attached to a northern spicebush seed is believed to inhibit the seed’s germination. A quick trip through a bird’s gut is just what the seed needs to more easily sprout.4

Animals also help spread the seeds of hard mast such as acorns. For example, blue jays and squirrels cache innumerable acorns in the fall, typically hiding them under debris or soil. Later, these animals will dig up and eat many of the acorns. Those that are overlooked may sprout into oak seedlings.5

Tent Caterpillars are For the Birds

Many bird species feast on caterpillars, which are leaf-eating machines. Eastern tent caterpillars, for instance, build silky tent nests in crotches of trees such as black cherry in the spring. These caterpillar colonies can strip a tree of all of its leaves. However, birds such as Carolina chickadees and the migratory black-throated green warblers tear open the tents in early spring, eating dozens of the young, small larvae, sometimes before they have done much leaf damage.

Later in the spring, yellow-billed cuckoos arrive from the south; a single individual can make a meal out of whole colonies of mature, two-inch hairy caterpillars. In fact, eastern tent caterpillars are a necessary mainstay of this cuckoo’s diet.

Other migratory birds—such as the ruby-throated hummingbird and the blue-gray gnatcatcher—snatch bits of the caterpillars’ silky tent to use in building their own nests, exposing more larvae to predators.6  7  8  9

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