Trees are fundamental to many ecosystems, providing habitat, oxygen, and a diverse food source for a wide array of animal life. Eating a tree encompasses various consumption methods, from leaves to wood and sap. Animals that consume parts of trees play a significant ecological role, influencing tree health, forest structure, and nutrient cycling.
Animals Consuming Foliage and Twigs
Many herbivores specialize in feeding on the leafy parts and tender new growth of trees. Deer are common browsers, consuming leaves, shoots, and twigs. Their feeding habits can significantly impact young trees and forest regeneration, especially when deer populations are high.
Giraffes are well-adapted to browse on the leaves and twigs of tall trees. Koalas have a highly specialized diet, relying almost exclusively on eucalyptus leaves. These leaves are tough, low in nutrients, and contain toxic compounds, yet koalas possess unique digestive adaptations to process them, including specialized digestive organs.
Numerous insects also target tree foliage. Caterpillars are known defoliators; they can consume vast quantities of leaves, potentially weakening trees, especially during outbreaks. Leafcutter ants cut and carry pieces of leaves back to their nests, where they use the vegetation to cultivate a fungus, which is their primary food source.
Animals Consuming Bark and Wood
Some animals target structural components of trees, such as bark and the underlying wood. Beavers gnaw on trees, eating the inner bark, particularly the cambium layer, which is rich in nutrients. They also consume young twigs and leaves.
Smaller mammals like rabbits and voles gnaw on bark, especially at the base of young trees, often resulting in girdling. Girdling, the removal of a complete bark ring, can interrupt the flow of nutrients and water, potentially killing the tree. Porcupines also feed on tree bark, particularly during winter months when other food sources are scarce.
Various wood-boring insects, including beetles, moths, and wasps, tunnel into and feed on tree wood. Many of these insects, such as bark beetles, target weakened, dying, or dead trees, playing a role in decomposition. However, some species, like the emerald ash borer and Asian longhorned beetle, can infest and damage healthy trees. Termites also consume wood, primarily cellulose; many species prefer dead wood, but some, such as Formosan termites, can infest living trees. Carpenter ants, unlike termites, do not eat wood for sustenance; they excavate tunnels and chambers within decaying or moist wood to create nests, often indicating underlying tree health issues.
Animals Consuming Sap and Roots
Some animals feed on liquid nutrients within trees or their underground root systems. Sapsuckers, a type of woodpecker, drill characteristic rows of small, precise holes into tree bark to consume the sugary sap that flows from these wounds. These birds target the phloem sap, which carries nutrients throughout the tree. Other animals, including bats, squirrels, and various insects, may also feed on sap made accessible by sapsuckers.
Aphids are small, soft-bodied insects that feed on tree sap by piercing leaves, stems, or twigs with their specialized mouthparts. As they feed, aphids often secrete a sticky, sugary waste product called “honeydew.” This honeydew attracts other insects, such as ants, which sometimes have a symbiotic relationship with aphids, protecting them in exchange for the sweet secretion. Spotted lanternflies also pierce phloem tissue to feed on sap, producing honeydew that can lead to mold growth on leaves.
Below ground, tree roots also serve as a food source for certain animals. Voles and gophers are rodents that can cause damage by gnawing on tree roots, particularly in orchards or young plantations. Certain insect larvae, such as those of root weevils, also feed on tree roots, potentially impairing the tree’s ability to absorb water and nutrients.