A tree hollow is a hole or cavity in a living tree. Holes can appear in tree trunks after a limb breaks off or the bark sustains injuries that expose the sapwood. This attracts fungi and bacteria that deepens the cavity. While a tree hollow may seem like a detriment to the tree, it’s an important part of the surrounding environment.

Types of Tree Hollows

Tree hollows can form in any tree, but they’re more likely to be found in older trees. Trees may self-prune lower branches as they mature, exposing an area that can then become a hollow. The size of the hole also depends on the age of the tree. It could take hundred of years for hardwood trees to form holes big enough to accommodate animals.

The Importance of Tree Hollows

Once a tree has naturally formed a semi-enclosed tree hollow, it becomes a natural resource in its environment. Tree holes are important habitats for many animals, such as various species of birds and other woodland mammals. They may deepen the tree hollow with their claws and beaks to make it more of a home. Even holes in fallen trees can be an important part of forests and woodlands. Animals and insects that travel along the forest floor use these holes for shelter and to find food. If a tree falls into a body of water, aquatic animals and organisms benefit from the tree hollows to live, hide, and lay eggs.

Animals choose a tree hollow based on various factors including:

• Entrance size and shape
• Depth
• Insulation
• Season
• Climate
• Location

Next time you see a hole in a tree, see it as more of a potential home than an imperfection.