Gray Squirrels’ Diet Changing
When you think of a Gray Squirrel’s diet, you think of nuts – acorns, walnuts, hickory nuts, etc., and for half of the year, these nutritious sources of food do serve as their main diet. Fall is spent burying individual nuts which will serve as their winter food supply. By spring, however, the fall stores of nuts and seeds are depleted, and it is one of the toughest times of year for these rodents. Tree buds, flowers, and the softer bark of some trees are their primary source of food. While abundant, buds and flowers are notably poor in calories and costly to digest. Finding and consuming food can occupy most of a Gray Squirrel’s day at this time of year. (Photo: Gray Squirrel eating Sugar Maple buds, spotted by sharp-eyed Lily Piper Brown)
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Signs of Gray Squirrel Nest-Building
Gray Squirrels use cavity and leaf nests throughout the year. Both types of nests are retreats used as shelter from the elements and protection from predators, as well as rodent-rearing homes. Signs of nest-building are plentiful at this time of year, when cold weather is around the corner. Evidence of this activity is present in the form of leafy ball nests (dreys) in trees as well as bare branches discarded on the ground that have had their bark stripped off and shredded. Squirrels line their nests with dried grasses, lichen and the soft fibers they remove from branches.
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Grey Squirrel Bonanza
The diet of the Gray Squirrel is extremely varied — from the cambium beneath tree bark, to tree buds, flowers and seeds, mushrooms, fruits, insects, frogs, bird eggs and much more. This year there appears to be a bountiful crop of American Beech nuts and Gray Squirrels will likely have a banner reproductive season next spring and summer as a result of it. Consisting of roughly 50% fat and 20% protein, American Beech nuts are one of the most nutritious seeds to be found. (Acorns are only about 9% protein.)
Historically, beechnuts were a popular food source in both Europe and America. Raw they contain the toxin saponin glycoside, which can cause gastric issues if you eat a large number, but if you’re willing to remove the husks and let the inner nuts dry for several weeks before roasting them, beechnuts can be a tasty delight. Many recipes – from beechnut pie to muffins and stew – can be found on the Internet.
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Gray Squirrels Mating & Making Nests
Gray Squirrels have two breeding seasons, one from December – March and another May – July (most females mate in the latter season and only mate once a year). At this time of year, polygamous male Gray Squirrels are aggressively chasing and checking out females to see if they are in estrus and if they are receptive. (An unreceptive female squirrel lets all suitors know in no uncertain terms – using claws and teeth – that she is not interested.) Male Gray Squirrels can smell females in estrus as far as half a mile away, so the woods are full of hopeful males these days.
Frequently litters this time of year are born in a tree cavity, while the second, late-summer litter is born in a leaf nest (drey). Cavities obviously offer more protection from the elements and predators than do leaf nests. Most den cavities have been created by decay, lightning, or woodpeckers and are lined with dry leaves, shredded bark and grasses. (Photo: Gray Squirrel collecting American Beech leaves to be used as a lining for her cavity nest.)
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Eastern Gray And American Red Squirrel Food Caching Strategies
Red and Gray Squirrels both store food for the winter, but their food caching strategies are very different. Gray Squirrels store many hickory, oak and beech nuts by engaging in “scatterhoarding” – burying one nut at a time, each in a different spot. Most popular are acorns, which fall into two groups — those grown by white oak species , and those from the group of red oaks. The acorns of red oaks have delayed germination, making them ideal for storage through the winter. Those of white oaks germinate sooner, in the fall, so are more readily eaten than buried. (If a Gray Squirrel chooses to bury an acorn from one of the white oaks, it often removes the embryo before doing so, which kills the seed and prevents germination.)
Red Squirrels, on the other hand, practice “larderhoarding” – collecting green cones in the fall (up to 15,000 or more) and storing them in one place (generally in the middle of their territory) where they are fiercely protected. A large pile (midden) can result, under which new cones are placed. This cool, moist environment keeps the cones sealed, protecting the seeds from being eaten by mammals and insects that are unable to open the cones. Middens can contain enough food to last one to two seasons. (Photo: Exceptionally large Red Squirrel midden submitted by Steve Bird of the Coastal Mountains Land Trust, Belfast, Maine)
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Some Ways Mammals Stay Warm In Winter
When temperatures drop significantly, mammals that stay active in the winter have a variety of ways to keep warm, one of which is to have layers of insulation to prevent their body heat from escaping. Often there is a layer of fat under the skin. In addition to providing a source of energy, fat doesn’t transfer heat as well as other tissues such as muscle or skin, and thus helps to insulate an animal’s body. The next layer consists of a short, dense coat of underfur which is filled with air pockets that provide insulation. Lastly there frequently is a third layer of oily, water-repellent guard hairs which excel at keeping out water. They are often transparent and hollow, providing extra thermal insulation.
Voles, mice, shrews and red squirrels use elaborate tunnels systems under the snow to escape cold temperatures and strong winds. Flying Squirrels huddle together in groups to keep warm. Shivering is a warming technique used by many mammals, including humans. And some active animals, like the pictured Gray Squirrel, simply find a sheltered spot in the sun, close their eyes, and soak up the warmth! (Thanks to Jody Crosby for photo op.)
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Red Elderberry Attracts Wildlife Year Round
The pollinated and fertilized white flowers of Red Elderberry (Sambucus racemosa) have recently developed into the red fruit for which this plant is named. Many people are familiar with its relative, Common Elderberry (S. canadensis), which produces dark purple fruit that is used to make jams, jellies, pies and elderberry wine. While Red Elderberry fruit can be used to make all of these, its raw berries are toxic. Red Elderberry’s popularity is greatest with pollinators, birds and four-footed mammals.
The cyanide-producing toxins in its flowers, (raw) fruit, stems, bark, leaves and roots do not seem to discourage wildlife’s attraction to Red Elderberry. The odor of its flowers, its nectar, and its highly nutritious pollen attract many ants, bees, wasps and flies. At least 50 species of songbirds eat the bright red fruits, including red-eyed vireos, ruffed grouse, song sparrows, gray catbirds, brown thrashers, and thrushes. Squirrels, mice, raccoons, and black bears also eat the fruit. Porcupines, mice and snowshoe hares eat the buds and bark in winter. The foliage is usually avoided by herbivores, although white-tailed deer and moose browse on it occasionally.
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Elm Seeds Important Early Source of Food For Wildlife
Tips of American Elm (Ulmus Americana) branches dropping on the ground alerted me to the fact that something was going on in the crown of the elm tree above me. Sure enough, a Gray Squirrel was busy dropping branch tips after harvesting the elm seeds on them. Because their seeds develop long before most seeds are available, elm seeds are sought after by numerous song birds, game birds and squirrels. This was verified by the presence of the Gray Squirrel, as well as a Rose-breasted Grosbeak and an Indigo Bunting (see photo), both of which took intermittent breaks to sing, but spent most of their time consuming elm seeds.
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Wing Prints In The Snow
Rarely have I had the good fortune to come upon a predator dining on its prey, but in this case, luck was with me. Seconds after I spotted a Red-tailed Hawk on the ground working on something it noticed me and flew away, perching within sight so as to keep an eye on its recent kill. This sighting eliminated some of the mystery of the story written in the snow. Wing prints would have revealed that the predator was airborne, and the wingspread might have narrowed the list of potential hawks/owls that it could have been, but determining the species would have been challenging without a sighting.
Although smaller rodents (voles, mice, etc.) make up a greater percentage of a Red-tail’s diet than larger ones, Gray Squirrels (whose remains are visible and were still warm) are consumed. The large numbers of Gray Squirrels on roadsides last fall reflected a booming population which most likely has provided ample food for many predators this winter, including this hawk. Interestingly, fur from the tail had been removed prior to the bird’s directing its attention to the internal organs of the squirrel. A quick retreat by this curious naturalist hopefully allowed the Red-tail to return to its meal.
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Eastern Gray Squirrel Diet Preferences
The diet of Eastern Gray Squirrels is extremely varied. Depending on the season, buds, fruit (such as the pictured crabapples being consumed), maple and oak flowers, berries, seeds, fungi, the inner bark of maple and elm, insects, and young birds are eaten. However, nuts are by far the main component, which is reflected in their distribution; the range of Gray Squirrels coincides strikingly with that of oak and hickory forests. Especially during the colder part of the year, nuts, acorns and maple seeds, or samaras, that they have stored for winter consumption are the mainstay of their diet. (Research shows that Gray Squirrels recover 85% of the nuts they store.)
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Red Squirrels Caching Food For Winter
Both carnivores and herbivores cache, or store, food for later consumption. Black-capped Chickadees tuck seeds into bark crevices. Bobcats may cover their kills with leaves, grass, snow and even hair from their prey’s carcass. Grey Squirrels bury their nuts individually, while Red Squirrels often hide green cones in a pile of cone scales (middens) that accumulate at the site where the squirrels have previously eaten seeds, keeping the young cones moist so that they will retain the seeds within them.
Red Squirrels sometimes go one step further than most animals that cache food — they frequently preserve their food by drying it before storing it. You’ll recognize this when you see it – an apple or mushroom stuck in the crotch of two branches. Sometimes the dried food is collected and cached near their winter quarters, but often it remains lodged in tree branches until eaten. The pictured mushroom, which was hung out to dry, was reduced almost to mush by the torrential rains we’ve had lately. Eventually it will dry out and remain edible into the winter.
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Oak Catkins A Source Of Protein
It’s common knowledge that you can often find warblers at this time of year by looking up into flowering oak trees, as the male flowers (catkins) attract an important source of protein for birds in the form of insects. Oaks (all parts) are host to more than 550 species of butterfly and moth larvae as well as many other invertebrates, many of which are attracted to catkins.
It turns out that birds are not the only creatures that visit oak catkins in order to secure a meal. Although we think of Gray Squirrels as consumers of nuts, seeds, fruit and fungi (and bird eggs and fledglings), their preferred food in the early spring includes the nutritious buds and catkins of oaks, elms and maples. Apparently their taste buds are not the same as humans’, as people who have consumed catkins say that their taste leaves a lot to be desired. (Photo: Gray Squirrel eating Red Oak catkins. Thanks to Sadie Brown for photo op).
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Gray Squirrel Dreys
With most deciduous trees having lost their leaves, squirrel nests, or dreys, are more noticeable. Red Squirrels, Eastern Gray Squirrels and Flying Squirrels all build dreys. Those of the Red Squirrel are round, grassy balls, 8” – 10” in diameter. In contrast, Gray Squirrel nests are usually larger and made of sticks and leaves. Flying Squirrel dreys are so high that they are rarely observed.
The dreys most commonly seen are made by Gray Squirrels. Usually 30 or more feet high, these shelters are typically built near the main trunk of the tree, in a crotch where several small branches meet, or on a strong, thick limb. Construction takes place in the summer or early fall, before trees have formed the abcission layers that cause leaves to separate and fall from branches. Therefore, the leaves on a drey’s branches tend to remain for quite some time, forming an effective water-shedding outer layer.
Branches are loosely woven into a foot-wide hollow sphere. The drey is lined with insulating grass, moss, leaves, and shredded bark. Usually there is one entrance/exit hole, facing the trunk (so as to keep rain out). Often squirrels build two dreys, giving themselves another shelter option should one nest be disturbed by a predator or overrun with parasites.
A drey is usually inhabited by one squirrel, but two are known to occupy a single drey in order to keep warm in the winter. Gray Squirrels give birth in late winter and again in the summer. A more protective tree cavity usually serves as a nursery in the winter, and the drey in summer. The average drey is only used for a year or two before it is abandoned.
Squirrels Digging For False Truffles
Such creative and informed answers to yesterday’s Mystery Photo, and many that were right on the mark! To set the stage, several 2” to 4”-deep holes riddled the ground under a stand of Eastern Hemlocks. Something had obviously been digging for something, but who and what? Close inspection of the holes revealed two things. The animal that had dug the holes had run into some thick hemlock roots, and with a clean 45° angle cut, had snipped them in order to have access to the soil beneath them. Secondly, some of the holes had pea- to marble-size, spherical tan objects that resembled puffballs both lying at the bottom and wedged into the sides of the holes.
Only because I had read Paul Rezendes’s Tracking & the Art of Seeing years ago did I recognize these holes and spherical structures within as the work of an animal looking for false truffles (a genus of fungi) to eat. By putting the various clues together – a hemlock stand, 3” to 6”-wide holes, clean incisor-snipped roots, and a few remnant truffles – the mystery at to what was being sought was solved.
As to who had done the digging, white-tailed deer, squirrels and porcupines all fancy false truffles. Both porcupines and squirrels have incisors that would make a clean cut through the roots. If porcupines had been digging here, there would likely be scat and/or quills lying about, which there were not. Thus, most likely it was a squirrel that had smelled, unearthed and eaten the false truffles.
Rezendes found that the truffles he discovered had dried spores inside them, and assumed that this made them undesirable to the animal that unearthed them and therefore they were not eaten. The spores of the truffles I found were not dried out, so I have no idea why they weren’t eaten, but I’m very glad they weren’t, as their presence allowed me to solve this mystery and see this phenomenon which I’ve been looking for for decades.
It may interest some to know that false truffles and Eastern Hemlocks have a symbiotic relationship. The fungi are attached to hemlock roots, so the minerals and water they absorb are available to the hemlocks. The hemlocks provide the fungi with sugars that they (hemlocks) produce through photosynthesis. Squirrels (and porcupines and white-tailed deer) and eastern hemlocks have a similar mutually beneficial relationship in that hemlocks provide the truffle-eaters with food, and the squirrels, porcupines and white-tailed deer disperse the spores of the truffles they’ve eaten. (Caution: Do not eat false truffles – they are considered toxic to humans.)
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Porcupines Foraging For Acorns
If you live near a stand of Red Oak trees, your chances of seeing a Porcupine this fall are greater than average. At the end of August, when the apple supply has dwindled, Porcupines move on to important new food sources – acorns and beechnuts. While American Beech trees in central Vermont have not produced a bumper crop of beechnuts this year, Red Oaks are experiencing a very heavy mast crop. These acorns provide sustenance for many animals – Black Bears, Red and Gray Squirrels, Eastern Chipmunks and other small rodents, White-tailed Deer and Wild Turkeys, to name a few.
Porcupines are typically one of the first acorn consumers, as they are able to climb oaks and eat the acorns before they drop and are accessible to many of the other animals that are limited to foraging on the ground. If you see the tips of branches nipped off with acorn caps (but no acorns) still attached lying under an oak tree, it’s likely that a Porcupine has been dining in the tree and discarding branches after scooping out and eating the acorns.If the tree is large, the Porcupine may reside in the canopy for several days. (Thanks to Emma for photo op.)
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Gray Squirrels Digging Up Cached Acorns
If you have oak trees in the woods near you, chances are great that their acorns attracted wildlife this past fall, one of which was most likely a Gray Squirrel. Unlike Black Bears, Wild Turkeys and White-tailed Deer, which eat acorns immediately upon finding them, Gray Squirrels tend to cache acorns for winter consumption. They do so by burying them individually, often in fairly close proximity to where they find them. (Red Squirrels also cache food in the fall, but typically bury numerous seeds, mostly conifers and maples, in one spot.) When food becomes scarce, as it usually does this time of year, it is possible to find numerous holes dug in the snow, frequently with leaves and bits of acorn shells littering the snow around them. Tell-tale Gray Squirrel tracks leading to and from these holes identify the excavator.
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Red Squirrels Dining on Black Walnuts
The method in which a nut has been opened depends on both the species of nut as well as the species of animal that opened it. To complicate things further, it can be difficult to ascertain who opened a nut as a given species, such as the Red Squirrel, often has more than one way of opening a nut. However, a given squirrel usually chooses one way to open a nut and consistently uses that method, so that if you come upon a pile, or midden, of nuts eaten by a Red Squirrel, the nuts will most likely all have been opened in the same way.
The beveled edges on the hole in the pictured Black Walnut, the fact that it was opened from both sides (leaving the dividing rib between the two sides intact), and the central location of the holes are indications that a Red Squirrel dined on the nutmeat. The chewing of open, jagged holes on either side of a nut is a Red Squirrel’s most common method of opening a nut. Gray Squirrels tend to remove the entire side of a walnut, as opposed to chewing a hole in it.
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Rodents Recycling
Bones, antlers, skulls, turtle shells – all are recycled relatively quickly by rodents seeking a source of minerals, particularly calcium and phosphorus. All rodents possess four incisors, two in the front of the upper jaw and two opposite these, on the bottom jaw. These incisors, unlike other teeth, never stop growing. By gnawing on hard objects such as bones, rodents keep their incisors paired down. If an incisor is broken or lost, the opposing incisor will continue growing in a circle, having nothing to grind against, causing the rodent to die of starvation or from having its brain pierced (through the roof of the rodent’s mouth) by the ever-growing incisor. In this photograph, a gray squirrel is obtaining minerals and sharpening its incisors on a moose skull that a human wedged into the crotch of a tree.
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Red Squirrels & Sugar Maples
We’re approaching what is often a very stressful time of year for many animals, including red squirrels. In the fall they feed on all kinds of conifer seeds, mushrooms, insects, nuts and the many fruits and berries that are available. They also have caches of cones, which they turn to once there is a scarcity of food elsewhere.
Once these caches are used up, usually by late winter or early spring, red squirrels turn to sugar maples for nutrients. Their timing is perfect, for this is when sap is starting to be drawn up from the roots of trees. Red squirrels are known to harvest this sap by making single bites into the tree with their incisors. These bites go deep enough to tap into the tree’s xylem tissue, which is where the sap is flowing. The puncture causes the sap to flow out of the tree, but the squirrel delays its gratification. It leaves and returns later to lick up the sugary residue that remains on the branch after most of the water has evaporated from the sap.
Not only do red squirrels help themselves to sugar maple sap, but they have developed a taste for the buds, and later in the spring, the flowers, of both red and sugar maples. Red squirrels are not the only culprits – gray squirrels and flying squirrels also make short work of buds and flowers from these trees.
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Gray Squirrels Caching Nuts
Many species of squirrels, including the red squirrel, are “larder hoarders.” Each individual stores its food in one central area that it defends aggressively against invaders. Eastern gray squirrels, however, are “scatter hoarders,” collecting and burying one nut at a time throughout home ranges up to 7 acres in size. It has been estimated that up to 25 percent of the nuts that gray squirrels cache are stolen by other gray squirrels. Researchers have found that gray squirrels engage in “deceptive caching.” Carrying a nut, a squirrel will repeatedly dig a hole and then fill it in, without depositing the nut. They also will cover a spot with leaves, even though they have not buried anything in this location. Where gray squirrel densities are high, the squirrels often keep a cache in its original location for only about three days before moving it to a new location.
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Discerning Eastern Gray Squirrels
In the fall, Eastern Gray Squirrels bury individual acorns from Red and White Oaks to sustain themselves through the winter. The acorns of Red Oaks have delayed germination – they can be stored up to six months before they start germinating. The acorns of White Oaks, however, have no such dormancy, and begin to germinate in the fall, soon after they fall from the tree. Once acorns sprout, they are less nutritious, as the seed tissue converts to the indigestible lignins that form the root. Gray Squirrels, as a means of “long-term cache management,” selectively remove the embryos from White Oak acorns (but not from Red Oak acorns) before burying them. Germination is prevented, and the storage viability of the White Oak acorns is extended by six months, equaling that of the Red Oak acorns.
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Shagbark Hickory Nuts Ripening
Shagbark Hickory, Carya ovata , a member of the Walnut family, is named after the shaggy appearance of the bark on older trees. Shagbark Hickory produces nuts which initially are covered with thick husks. As time goes on, the green husks turn brown and open, exposing the nuts, which fall to the ground if squirrels haven’t managed to eat them while they are still on the tree. It takes about ten years for a Shagbark Hickory tree to start producing nuts, but large quantities are not produced until it’s 40 years old. Nut production continues (a good crop every three to five years) for at least 100 years. Shagbark Hickory nuts are very sweet and highly nutritious. They were a staple food for the Algonquians and squirrels, raccoons, chipmunks, mice, bears, foxes, rabbits, wood ducks and wild turkey also feed on these excellent sources of protein, fats and carbohydrates.
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Red Squirrel Gardens in the Woods
Red and Gray Squirrels remain active year round, and thus, need to have access to food throughout the year. In order for this to happen, seeds and nuts must be stored in the warmer months for consumption during the winter and early spring, when food is much harder to find. While Gray Squirrels tend to bury nuts and seeds individually for this purpose, Red Squirrels often cache numerous seeds (mostly conifers and maples) in one spot, dispersing these caches throughout the woods. During the winter Red Squirrels use their memory (and sometimes their sense of smell) to locate these buried treasures. Inevitably some are overlooked and in many of these cases, the seeds germinate. Finding little patches of multiple seedlings, such as this miniature stand of young Sugar Maples, is a good indication that at least one Red Squirrel overwintered in the vicinity.
Naturally Curious with Mary Holland 
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