Eating tree bark probably seems very unappealing to humans. However, tree bark actually provides a plentiful amount of nourishment for many animals with the right digestive system, particularly during the winter when other food sources are more limited.
This tutorial will show us five creatures that consume tree bark and explain how they obtain nutrients from this type of wood.
Why Do Animals Eat Tree Bark?
Plants have cellulose, hemicellulose, and lignins in their cell walls, and pectins hold individual cells together. Complex carbohydrates called cellulose and hemicellulose can only be broken down by certain animals that have the enzymes called cellulase and hemicellulase to do it. The microorganisms that reside in the digestive tracts of animals that consume bark yield both cellulase and hemicellulase. For animals that consume bark, the pectins and pectic acids that bind adjacent cells together supply glucose. Nevertheless, lignin is the least digestible substance since the majority of animals that consume bark lack the microorganisms that generate ligninase, the enzyme required to break down lignin.
The majority of the dead, crushed cells that make up the bark’s outer layer have a high lignin content. On the other hand, the living cells that make up the inner layer of bark contain complex carbohydrates, sugars, and minerals that animals that consume bark may absorb.
Tree bark is edible to every species of deer in the Cervidae family. This is particularly typical in wintertime arboreal settings.
One type of ungulate animal with even toes that chews on regurgitated food from a stomach chamber called the rumen is the ruminant, which includes deer. The stomach of a deer is separated into four chambers, just as that of cattle. The rumen, the first chamber, is where the bacteria needed to manufacture the enzymes needed to break down tree bark are found.
Deer will eat by biting off only a portion of the bark from trees and then swallowing it whole. When the deer are allowed to rest later, they chew and regurgitate the rumen bark until it has been sufficiently mechanically and chemically broken down to move on to the reticulum, the stomach’s next chamber.
Animals That Eat Tree Bark: Beavers (Castor spp.)
The two beaver species that are still in existence, the Eurasian beaver (Castor fiber) and the North American beaver (Castor canadensis), will remove and consume the bark from trees. Beavers mostly eat small tree trunks, sapwood off branches, and the bark from new twigs. This youthful, pliable bark has a lower lignin content.
Beavers eat primarily bark and other woody plants during the winter. These ingenious creatures will store strips of wood under their shelters in the summer so they have food for the winter. Their strong molars and constantly expanding incisors chew through the wood, breaking down the fibrous parts of the bark.
Rabbits (Leporidae) have a very weak digestive system, yet they have evolved a way to chew through and consume tree bark in the winter. Food moves through their stomach very fast since it is quite simple, but a large variety of symbiotic microbes in their colon improve food digestion significantly.
Rabbits will engage in coprophagy—eating their own feces—in order to significantly improve their capacity to digest the cellulose in tree bark. After being re-ingested, the food goes through the microbially rich colon several times, during which time the amount of cellulose digested can increase by two to three times.
Tree Bark-Eating Animals: Porcupines in North America (Erethizon dorsatum)
The North American porcupine (Erethizon dorsatum) often climbs trees in the winter to feed on twigs and the inner bark of various tree types.
Because of its elongated big intestine, porcupines have a slower rate of intestinal transit, which promotes better nutrient absorption. Additionally, a significant portion of the microbes that make hemicellulase and cellulase are found in its large intestine. Additionally, the North American porcupine will fully chew the bark until it resembles dust, which will significantly improve digestion.
Water Vole (Arvicola amphibius)
The water vole (Arvicola amphibius) will peel and consume the inner layer of bark from small, young trees and shrubs during the winter months when alternative food sources are few. They effectively remove the tough outer layer of bark to reveal the softer, more digestible cambium layer since their digestive system is not strong enough to break down the tougher portions of bark.
Usually, these little rodents will feed on tree bark that is no more than eight inches above the ground. Frequently, they will remove a full circle of bark from the tree. Girdling is a procedure that can kill or severely harm young shrubs and trees.