Firmly anchored in the space between the main trunk and a large branch of a silver maple tree, this winter drey is home to a St. Charles fox squirrel.
Good Natured: Squirrel Dreys
November 27, 2020
There’s no place like home. Dorothy Gale said it as she clacked her ruby slippers together, and Perry Como and the Carpenters sang about it, noting that it’s even better at the holidays.
In fact today, given our COVID mitigations, we often find we really have no place BUT home.
With the prospect of a long, cold winter just ahead, we want to make sure our chosen domiciles are warm and snug. We caulk around our door and window frames; we toss extra insulation down in the attic; we pile extra blankets on the bed and thumb our noses at Ol’ Man Winter.
But you know whose homes are the warmest? The most windproof and waterproof? It’s not yours, and it’s not mine.
Oh I know they don’t look like much. A pile of leaves high in a tree. How could they possibly offer any sort of protection from the elements?
I tell you though, they do. Driven by instinct, but certainly with some learning along the way, our local squirrels create some of the best-engineered winter homes around. Twigs, often gnawed from a tree when the leaves are still intact, form the framework upon which layer upon layer of more leaves are stacked, woven and stuffed. The thick walls of overlapping material keep wind, water and snow from penetrating to the interior, while pockets of air provide insulation that keep cold air out and warm air in.
How successful are these structures? Numerous studies have tracked the temperatures inside of squirrel nests-which, incidentally, are sometimes referred to as dreys. Researchers in Lapland, where winters are c-c-c-cold, found that dreys routinely measured 20C to 30C (that’s 68F to 86F) warmer than the ambient air temperature, provided the squirrel was tucked inside providing body heat. Researchers monitoring dreys in Russia, where it’s also quite c-c-cold, noted similar results.
Closer to home, in the woods of Maine, where it’s still ch-chilly, Bernd Heinrich-one of my favorite naturalist-authors-has examined the materials and designs of all sorts of nests, including those of gray squirrels. In Winter World-one of my favorite nature books-Heinrich describes the structure of a gray squirrel drey that blew down during a rainstorm. (Okay, so maybe that calamity shoots a tiny hole in my statement that these nests are weatherproof. But I’ll bet it’s the only nest, ever, that’s suffered such a fate…lol…)
During his investigation Heinrich found that the 12-in. diameter nest featured 26 layers of oak leaves–flattened, dried and overlapped like shingles-that sheltered a 1 1/2-in. layer of shredded bark, which ensconced a 3 1/2-in. wide central chamber. The layers inside the leaves were all bone dry, despite the nest having come down during a driving rain. Home sweet home at its finest!
So at this point you might be wondering, “This is all great for the squirrels. But how does it affect me?”
Well, truth be told, other than knowing our local squirrels retreat to well-insulated nests on cold winter nights, your direct benefit from dreys could stop right there.
Or it could save your life.
That’s right. Creating a framework of sticks and twigs, then insulating it with leaves, is commonly taught as a method of wilderness survival. Known as a debris hut, it’s based on drey construction methods and keeps its human occupant warm and toasty-just like those squirrels in Finland, Russia and Maine.
Talk a look around your neighborhood and, so long as there are trees, it will not take you long to find one with a leafy nest. Examine it as best you can from a distance-most squirrels like to build at a height of around 30 feet-and see if it looks like a well formed ball of leaves. If it does, congrats! You’ve found a winter drey.
But if it’s loosely constructed, flat or falling apart, you might have found a summer drey, or even a fake one. In Winter World, Bernd Heinrich tosses out this latter possibility after having examined many dreys he called junk. He also mentions that squirrels may build these phony nests as a way of deceiving drey-raiding predators.
At any rate, once you’ve found one solid squirrel nest, see if you can find another, and another. Tree squirrels, both gray and fox, are plentiful throughout our area, and they all need a place to call home. But the savvy squirrels-most who survive their first year qualify-don’t stop with just one dray. Building at least two means the animal will have a backup when the gales of November, or really any winter month, come early. A spare will also come in handy if fleas or other parasites proliferate, or if a marauding owl or raccoon destroys a drey.
In its heart of hearts, every squirrel would no doubt prefer to have a tree cavity to call home. Even the sturdiest dreys can’t compare to a house made of wood. But such accommodations are rare indeed, especially in our suburban environments. So dreys it is.
Warm, dry, safe, secure. Even if it’s just a ball of twigs and leaves, there’s no place like home.
Pam Otto is the outreach ambassador for the St. Charles Park District. She can be reached at 630-513-4346 or firstname.lastname@example.org.