If hardwood trees grow in your yard, each autumn many of them shed their leaves and litter your lawn with literally thousands of dry leaves. While most homeowners consider them a nuisance, they are valuable to wide range wildlife; one of these animals is the gray squirrel.
One way that squirrels use them is to construct leaf nests (sometimes called dreys). While such structures are used throughout the year, often we do not know they are there until the hardwoods shed their foliage.
The structures are round balls up to two feet more in diameter and are typically built in hardwoods (particularly those that bear nuts) 20-40 feet above the ground. Often these winter nests are located near the trunks of trees. The nests consist of a frame fashioned from branches, however, the bulk of the nests are composed of leaves, twigs, moss, strips bark, and sometimes even feathers or fur.
The nests are built to provide the animals with shelter during the winter. The best wintering sites are hollow trees; however, there are rarely enough tree cavities to meet the needs of woodpeckers and other critters that also roost in tree cavities in winter. During the coldest nights of the winter, the temperature inside a tree cavity may be as much as 30⁰F warmer than the night air. Leaf nests are never as warm natural cavities yet they do insulate gray squirrels from frigid weather. Since more than one squirrel sometimes use the same leaf nest, the animals’ combined body heat they generate help keep the nests warm enough to enable the squirrels to survive cold weather.
This winter, if a leaf nest exists on your property, on a frigid winter night if you look out your window and see it silhouetted against a full moon, it is comforting to know that some of the autumn leaves that fell in your yard are helping keep gray squirrels alive.
