This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
This post was originally published at Urban Science Adventures! © on January 23, 2009 as Urban Wildlife Watch: Squirrels and Dreys.
Squirrels are rodents, so that means they are cousins to chipmunks, mice, rats, voles, and beavers. They are members of the Sciuridae family, which means 'bushy tail' and is a perfect way to describe the many members of the squirrel family - tree squirrels, ground squirrels, even chipmunks and groundhogs. But, my focus here are the typical tree squirrels. Through-out much of the Mid-west, Mid-South, and Eastern United States and Southeast Canada, the Eastern Gray Squirrel is a very common wildlife neighbor in cities and towns, big and small.
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Eastern Gray Squirrels are arboreal (the live in trees) and are tied to forest or wooded ecosystems. They depend on trees for food - various types of seeds, nuts, berries, and fruits - and for shelter. For a long time I believed squirrels only lived in hollow trees. They will live in tree hollows, but they also build nests. I learned this in college when I completed a biology class research project on squirrel animal behavior. The nests are called dreys. Squirrels gather dead leaves and twigs. The dead leaves make great insulation and they wedge the materials in the forks of trees, at the higher parts of the tree.
Very large hollow in a Sycamore tree, that looks like it might be a great squirrel home.
Squirrels will make and live in several nests. As fleas and ticks become a problem in a single nest a squirrel will abandon its nest, and the female will transfer all of her babies of she has any.
Squirrel nest in a Sycamore tree in the summer time. I'm standing under the tree to get this shot. Looking at the tree from a distance, the large green leaves of the tree make it hard to detect the nest. Now that it is winter time, dreys are much easier to spot.Squirrel nests in a sweet gum tree.
Two squirrel nests in one tree. Very likely, these nests belong to the same squirrel.Close-up of one of the nests. Notice how the drey is wedged in the fork of the tree.
The series of pictures below are of a squirrel I spied in my backyard with a mouth filled with nesting material. There are some squirrel nest in my backyard, but sometimes they will build nests in "artificial hollows", like an attic, as you will see in the video below. Here is a video of the same squirrel.
