Josephine and I were venturing furtively down the peagravel driveway of some unknown neighbor to examine the ground beneath the outermost circumference of a great oak. I had told Josephine we were collecting acorns, but I had an ulterior motive: I hoped to find the half-eaten acorns that served as clues to a mystery I’d discovered in my squirrel books. Josephine was in it simply for the joy of acorns. She delights in the geometric curiosities produced by trees and bushes (seedpods, catkins, drupes) and occasionally will bring them home for me. I keep these gifts on my desk until they burst open or otherwise turn into a mess.
When I’d asked Josephine if she had any interest in joining me in an acorn hunt, she replied, “Of course!”
She had just turned three and was all blond curls and dimples. She was wearing a purple dress with a horse on the front that she’d gotten for her birthday. It was just long enough to hide the dirt on her knees, but not long enough to cover the scabs from the mosquito bites she’d scratched till they’d bled.
The oaks in our neighborhood are coast live oaks, an evergreen species that produces sharp, bulletlike acorns. When young, these acorns are green at the pointed end fading to buttery yellow under the cap. They are silky smooth to the touch.
There were no acorns under the first few trees. Then we came to a big oak hanging over a driveway, and there they were everywhere. I ventured a few steps onto the gravel to retrieve one, and then a few more for another. Josephine scampered ahead of me, between two parked cars. I looked at the acorns in my hand. Just as I’d hoped, each had a bite taken out of it, near the top.
I was looking for something that Michael Steele, a squirrel researcher at Wilkes University, had noticed back in 1986. He was checking on squirrel nest boxes in a forest in the Sandhills of North Carolina when he and his companions noticed something strange. That year, the turkey oaks had produced a “dense blanket of acorns in the leaf litter.” Nut trees and conifers periodically produce these bumper crops in what’s called a mast year. When the researchers knelt to investigate they saw that “each of the thousands of acorns was partially eaten, not in a haphazard way but neatly and consistently from the top,” Steele later wrote. That night, after they’d finished counting squirrels in nest boxes, they sat around and puzzled over the acorns. The mystery was, as Steele wrote, “why would any squirrel, or any animal for that matter, invest the energy to eat a small portion of a single food item, only to pick up another and repeat the process?” The squirrel chips away the tough outer shell to expose the acorn meat, then only takes half the payment promised for its labor. Why?
When they returned to Wake Forest University (where Steele was teaching at the time) they found the same thing: half-eaten acorns beneath the local willow oaks. Steele grabbed a handful of acorns and took them to a university museum, where he found some squirrel skulls. The incisors fit the tooth marks in the acorns perfectly.
When Josephine returned, she carried two more acorns, each marked by what looked like an incisor bite that pierced the shell of the acorn, but then went no farther. It was just a single bite, which was different from what Steele had seen: The acorns he had found were precisely half-eaten. When I asked Steele about the single-bite acorns Josephine and I had found, he said we were looking at something different. “Right now, the acorns are still developing and the squirrels are sampling the tissue,” he said. In other words, squirrels, tempted by not-quite-ripe acorns, opened the shell, took a bite, and (blech!) threw it to the ground.
Steele has blue eyes, a graying goatee, and a gentle manner. He became a squirrel expert almost by accident; his real interest is relationships—the diplomacy and deals negotiated between plants and animals that end up shaping entire landscapes. When Steele began asking around about acorns, he told me, researchers from around the county said they were seeing squirrels—and birds too—leaving acorns half-uneaten, especially during mast years.
On a hunch, the researchers tried sprouting the half-eaten seeds. Lo and behold, they germinated, and for some species, more sprouted from the half-eaten seeds than from the ones left whole. Every species relies on partnerships to survive. It seems that oak trees and squirrels had worked out a deal: The squirrels get to eat acorns, but not the whole nut. In return, the squirrels disperse the seeds, and even bury some of them. Perhaps squirrels are planning generations ahead, planting the next crop of oaks.
The reason for a squirrel is redistribution. It is a great leveler of abundance and scarcity: a shock absorber in rodent from. The squirrel’s body and character were shaped by the overriding factor in their existence: their evolutionary partnership with trees, which produce a lot of their food all at once, and then nothing for the rest of the year. And so everything about a squirrel is focused on the imperative to turn boom and bust into steady living.
Squirrels eat a lot of other things besides tree nuts: plants, underground fungi, insects, bones, sometimes baby birds, and even in some cases each other. Some catch fish. But they have a special relationship with nut trees. When there are plenty of nuts, squirrel populations swell, and when nuts are scarce, they die. Like humans, they make supplies last by harvesting and storing. A lot of animals simply sleep through the lean times by building up fat when food is abundant and then hibernating, but not tree squirrels. The species that live in our cities stay active all winter. They eat as much as they can in the fall and put on a layer of fat, but it only amounts to about 10 percent of their body weight. That’s the equivalent of a 180-pound guy like me gaining 18 pounds—a lot, but not enough to last all winter.
Squirrels are much better at burning fat than gaining it. When temperatures drop, some internal switch flips and they begin to turn fat into heat thirteen and a half times faster than normal. This performance “stands as one of the best among animals,” according to Steele and his fellow squirrel researcher John Koprowski of the University of Arizona. Without even moving, they then can produce energy like a pro cyclist powering up into the Pyrenees.
And so squirrels are able to smooth out the fluctuation between scarcity and abundance, first by hiding away calories in food caches, and then by converting this fuel in an efficient internal furnace.
Hibernation might seem like a safer strategy, but hibernation is inflexible. If someone destroys your home in the middle of a three-month nap, you are dead. As climate change shifts the timing of winter temperatures, many hibernating species are struggling. Belding’s ground squirrels in Yosemite, for example, rely on a thick layer of snow to insulate their burrows during hibernation, and they have been killed when an unseasonable thaw floods their nests. By staying awake, city squirrels are better able to adapt to changing conditions and take advantage of disrupted patterns. Small wonder that they thrive alongside humans, since our survival strategy is the same.
From another perspective, however, it is a great wonder that squirrels thrive alongside us because they were shaped before the first Homo sapiens ever walked the earth. They are identical to the squirrels that lived five million years ago, as far as biologists can tell. This, then, is the second great squirrel mystery: How is it that these ancient beasts have managed to thrive in our cities when so many other species have simply died off?
One cloudy morning I arrived at a coffee shop across the street from the UC Berkeley campus to meet Mikel Delgado. Delgado is a grad student who studies squirrels, which means that, rather than traveling to the rain forest to trap butterflies or scuba diving to observe whales, her subject of research is directly outside her door. Squirrel habitat is almost 100 percent coincident with student habitat.
She was waiting for me at an outside table, wearing a brown Carhartt sweatshirt, a green knit scarf, and purple glasses with gray checked temples. Her hair was black, with a few strands of white, and pulled back. She smiled and suggested we walk to her office.
“I’ve only just begun my research,” I told her. “You can assume total ignorance.”
She scanned for squirrels as we strolled, and seemed disappointed when they did not immediately appear. “It’s still early,” she said. “They may not be up yet. They are adapted to the schedules of the students.”
That is, because the people around them are not early risers, neither are the squirrels. They are attuned to their food sources’ rhythms, whether they be the seasonal production of tree nuts or the time of day at which college students are most likely to flip pizza crusts toward a charming tree kitten.
A pair of crows called from a treetop as we approached, and Delgado explained that squirrels react to crow alarm calls. The crows seem to sense danger a little sooner than squirrels do.
When we got to her lab, Delgado opened a big plastic tub filled with neatly partitioned nuts. She stowed a few handfuls of these in a fanny pack: pecans, walnuts, and almonds, all in their shells.
As soon as we emerged we began seeing squirrels. “Watch this,” she said, tossing a nut to one that approached us. “You’ll see he turns it ’round and ’round in his mouth, and he’s just feeling for what’s the best way to carry it, and maybe also checking for imperfections in the shell. If it’s cracked he might eat it right now rather than burying it and having it go bad.”
“How do they crack something like a walnut?” I asked.
“They have incredibly strong jaws. Before I started studying squirrels I got bitten by one while feeding it, and it really hurt. They have poor close vision, so they can’t see which is the nut and which is the finger. They have relatively clean mouths, they don’t often carry rabies, but they can carry other diseases, so it’s not a good idea to touch them.”
As she was saying this, another squirrel approached and pawed at my pant leg. “Step back!” I cried.
Delgado tossed a walnut directly at the beast’s head. It dodged nimbly and picked up its reward.
“So he’ll turn it,” Delgado said, “and then if you watch carefully, they do this headshake.”
I watched.
“There.”
I had seen nothing.
“It’s very fast. There was a student here, Stephanie Preston”—now a professor of psychology at the University of Michigan—“who first noticed it. All these squirrel scientists had been observing them for years and no one had ever described this.”
It took me a good half hour of close watching before I saw it. A few months later, watching videos of squirrels, I found it had become invisible to me again, and it only reappeared after I watched a video in slow motion.
It’s almost a flinch, a jerk over one shoulder and back. Scientists still aren’t sure why they do this; maybe they get a sense for the quality of the nut by rattling it in its shell. If insects have partially eaten an acorn, a squirrel will eat it immediately (along with the insects) rather than burying it.
Delgado studies the way squirrels store food. Different species have different food-storage strategies. First, there are the larder hoarders, which put all their nuts in one place and defend it. Then there are the scatter hoarders, and city squirrels fall in this category. It’s a diversified investment strategy: If someone else pillages a storage place, they lose just one nut. The problem with scatter hoarding is that squirrels end up with thousands of nuts all over the place, and they have to remember precisely where each one is, or else it’s gone forever.
It’s impossible to compass the enormity of this problem unless you’ve tried to do what a squirrel does. Forget about remembering the locations of thousands of nuts—do you suppose you could remember a single location? And to make things easier, instead of remembering that location for three or four years, as squirrels do, do you think you could remember it for just, say, five seconds? When I tried to do it, it resulted in utter, humiliating failure.
The squirrel had taken Delgado’s nut about fifteen feet away. It scratched at the surface for a couple seconds, deposited the nut, and then bent over to tamp it down with its teeth, arching its back and pumping twice. Then it brushed some dirt and pine needles over the spot and was off. The whole operation was over in a quarter minute.
Delgado suggested we try to find the nut. At first, this seemed a little bit unsporting. After all, I’d never taken my eyes off the spot where the squirrel had been. But I gamely walked over. Then, as I crouched down, something curious happened. The ground in front of me dissolved into an undifferentiated pattern of sticks and leaves and tufts of grass. Had the squirrel been right here? Or was it perhaps a half foot to my right? That actually looked more likely, and that’s where there was a bit of pine needle duff overturned, with the wet underside facing the sun. I brushed this away, but there was no sign of disturbed soil. I dug up a bit of ground with a stick. Nothing. Compacted clay. The idea that a squirrel had just made a hole there seemed impossible. I turned back toward my original spot, but I couldn’t pinpoint it now, and I noticed glumly that Delgado was searching several feet away. I disconsolately turned over more leaf litter. It was utterly hopeless. I’d have to dig up yards of dirt to find this nut. It did make me feel a little better when Delgado came up empty as well. Often she does find the buried nut, but not always. “This is just something that squirrels have evolved to be very good at,” she said. “Hiding nuts is one of their specialties.”
For many years researchers suspected that squirrels actually did not remember where they buried their nuts, and instead simply sniffed the ground until they located any subterranean stash at random. But the leader of Delgado’s lab, Lucia Jacobs, showed that this was not the case. Squirrels do sometimes stumble across (and eat) the nuts of others, but the vast majority of the time they dig up the nuts that they themselves have stored.
Henry Thoreau wondered at this as he tromped through the snow around Concord, Massachusetts. “In almost every wood, you will see where the red or gray squirrels have pawed down through the snow in a hundred places, sometimes two feet deep, and almost always directly to a nut or pine-cone, as directly as if they had started from it and bored upward.”
The problem here is not just that you have to remember that there’s a nut buried under the juniper bush (as it was in this case), you have to remember precisely which square inch under the juniper bush it is. Then multiply that by five thousand. Delgado wonders if it’s based on some kind of geometric mnemonic, with each squirrel filling in dots that sketch a shape, perhaps a giant spiral.
This brings us back to the mystery of the half-eaten acorns. The mystery must touch, in some way, the symbiotic relationship between squirrel and oak.
No matter how good the memories of squirrels, they fail to retrieve some seeds in periods when their larders outlast the hungry times. And when a squirrel dies, its trove might eventually grow into a forest. Squirrels provide a service to trees by distributing and burying their seeds far beyond the patch of dirt where they fell. Acorns buried by squirrels have a much better chance of growing into sprouts than those that fall atop the leaf litter.
But these mutually beneficial deals are never completely harmonious. In nature, no species ever settles on the terms of a partnership for long. Instead, the parties are constantly renegotiating their agreements, always edging for a slightly better deal. The oak and the squirrel aren’t exactly allies. I started thinking of them as a pair of crusty old Hollywood producers: They’ve known each other since they were young, have profited tremendously from doing business together, and they enjoy joshing each other with affectionate obscenities over drinks. But each loves nothing more than finding some devious way to cheat the other.
White oaks, for example, made what looks like a bid to game the terms of the coevolutionary contract by producing acorns that germinate rapidly, sprouting soon after they are buried. To thwart this strategy and still reap the energy in the nutmeat, squirrels eat these nondormant seeds rather than burying them. When they do decide to bury a nondormant acorn, they first gnaw out the embryo, transforming the seed into an inert mass of calories that cannot sprout.
Steele and other scientists investigating half-eaten acorns have found that an acorn has more fats, which squirrels like, in its top half, and in its bottom half, around the embryo, there are more tannins, which squirrels dislike. Tannins—the same chemicals that make wines “dry”—are poisonous in high concentrations. They are a mainstay of plant chemical warfare, used by everything from apples to persimmons. That feeling of all the moisture being sucked out of your mouth when you bite into an acorn or an unripe apple comes from the tannins you’ve just released, which act as molecular vacuum cleaners, hoovering up all the proteins that make your saliva feel slippery. Unlike squirrels, humans can’t eat acorns without processing the tannins.
The researchers thought they’d found the answer: The oak trees are giving the squirrels half of each acorn, yet protecting the important bits. And, it seemed, guiding the squirrels to the more delicious half of the acorn with its shape. When a researcher whittled acorns so the top looked like the bottom and vice versa, the squirrels ate the wrong end: the one containing more tannins, less fats, and most importantly, the embryo. Squirrels use the shape of an acorn to find the tastier end, just as we use the shape of an apple to bite into the flesh rather than the core. If a team of devious scientists reshaped our apples so the core ran widthwise, we might find ourselves inadvertently eating it.
When squirrels are hungry, they always eat the whole acorn. But when there is an abundance of them, they will just eat the best part and discard the rest. This may explain the evolutionary logic behind a mast year: By producing gigantic pulses of nuts, oak trees ensure that some of their acorns will make it past the predators. The same logic drives trees, even in normal years, to produce all their nuts or fruits within a small window of time. The tree evolved toward boom and bust. The squirrel is a shock absorber. By working to bamboozle each other, they work together.
Of course, squirrels eat more than acorns, and their options are especially diverse when they live among humans. Humans frequently put out buffets of seeds from which squirrels can eat their fill. The humans, however, usually intend these seeds for wild birds and view the squirrels as unwanted guests. You probably know some of these humans.
There’s a whole genre of Internet videos and forums dedicated to the contest between humans and squirrels for control over bird feeders. I have a book on the subject: Outwitting Squirrels: 101 Cunning Stratagems to Reduce Dramatically the Egregious Misappropriation of Seed from Your Birdfeeder by Squirrels, by Bill Adler Jr. The fact that humans must summon this much collective brainpower and earnest scheming to match wits with a one-pound rodent says something not so complimentary about us. At the end of his book, Adler urges his readers not to give up and admit defeat:
I have high hopes for civilization. We have survived world wars, the cold war, devastating plagues. We have gone to the moon, and sent probes past the outermost edge of our solar system. We have eliminated major diseases, and we have invented Wheel of Fortune.
But only if we keep up our struggle to outwit squirrels can humankind expect to progress towards the next level of development, whatever that may be.
Late one night, lost deep in the Internet of squirrels, I stumbled across a series of videos by Steve Barley that offered an admirable alternative to the no-holds-barred warfare I’d grown used to seeing, and I was moved to write to him.
Barley, who lives in suburban Hertfordshire, England, entered into his relationship with squirrels in the traditional way: They destroyed his bird feeders, and he got annoyed and started looking for ways to stop them.
His local squirrels severed the rope supporting one feeder, sending it crashing to the ground. Squirrel incisors also made quick work of his plastic feeders. Next, Barley bought steel feeders covered in wire mesh. Of course these didn’t deter them either. But as Barley watched the squirrels dismantling the defenses, instead of growing angry, he began to feel something resembling admiration.
“It was only when I watched them figure out how to hang upside down on the wire mesh “squirrel-proof” ones and then widen a hole low down with their teeth and claws to get the nuts out like in a gumball machine that I began to respect their ingenuity and acrobatic skills,” he told me.
“They were fascinating to watch, especially the way they can reverse their rear claws to hang on with ease, leaving their front paws to do their stuff.”
Squirrels have hinged ankles that rotate 180 degrees. For comparison, imagine a ballet dancer going up on pointe; that’s not quite ninety degrees. This flexibility allows squirrels to drape themselves over the shields and baffles employed by some bird feeders. Squirrels also have the right sort of brain for this sort of thing. They are problem solvers, Delgado had told me, motivated and persistent. And though they lack opposable thumbs, they have good motor skills and dexterous fingers.
As Barley and his son were watching the squirrels empty the feeders, he hit upon the idea of hanging one off a clothesline, just to see how they would manage it. This was not much of a challenge: The squirrels made what had looked like an impossible leap from a bird platform. At this point, Barley’s annoyance ceded to curiosity: How much could these squirrels do?
“We experimented with a piece of trellis,” Barley said, “and they jumped onto that to reach the feeder hanging further down the line.” He and his son were playing with the squirrels now rather than against them, and kept adding bits and pieces to the collection of obstacles: an old ironing board, a plunger, a bicycle mudguard, a lampshade, and on and on.
They filmed squirrels making short work of this obstacle course, and, as is the way with these things, it ended up on You-Tube, where it became a minor sensation.
As amusing as Barley’s contraptions are, they don’t truly test the outer limits of what squirrels are capable of doing. The closest we have ever come to accomplishing that was in 1999, when the BBC built an obstacle course for a series about squirrels called Daylight Robbery (Barley hadn’t seen it when he started building his own in 2010).
To beat this course, squirrels had to climb up through a vertical pipe, leap onto a blade of a spinning windmill, cling to it, and then sail off on the right trajectory to land on a platform. Then they had to go paw over paw upside down along a suspended chain that passed through a series of spinning disks, negotiate a revolving door, run through a slack canvas tube, and keep their balance while crossing a pole covered with slick spinning rollers. From there, it was a six-foot jump to another tunnel, through which they had to ride a sliding vehicle made to look like a rocket ship by pushing it along with their paws. Finally, there was an eight-foot jump to the food.
This challenge took the squirrels a little over a month to figure out. They mastered the obstacles with varying levels of grace—one female learned to complete the course without hesitation or error each time she tried, earning her the starring role in the production.
Despite their skills, squirrels are not known for their cunning, or their athleticism. Squirrels are known for their teeth: They have no canines, so they have their distinctive incisors sticking way out in front and then a honking gap between those and their molars. The incisors have a chiseled edge that’s sharpened by use. These grow continuously throughout life (as is the case with many rodents), and squirrels must wear them down.
Squirrels are also known for their tails. The tail becomes an effective blanket when it is cold, an umbrella when it is wet, and a cooling system when it is hot. In hot weather a squirrel can dilate arteries at the base of the tail to allow blood to rush down its length, where the heat from its core may dissipate.
The scientific name for the squirrel genus is Sciurus, which translates roughly to “shade-tail.” The squirrels in North American cities are eastern grays (Sciurus carolinensis, “Carolina shade-tail”) and eastern fox squirrels (S. niger, “swarthy shadetail”). The eastern grays also come in black—as do many of those around Washington, DC—and there are a few populations that are entirely white.
Eastern grays were the first to populate cities, but fox squirrels, which are larger and have bigger brains, are pushing them out in some places, like my town. Fox squirrels have darker coats, with a ruddy orange fringe along the bottom by their paws.
Outside cities, there are several others: the western gray in the Sierra Nevada, the Arizona gray and Abert’s squirrels in the Southwest, and the Eurasian red across the Atlantic. In England the red squirrels have retreated to the northern conifer forests because they are unable to cope with the diseases introduced by eastern grays—one native American species taking retribution for smallpox and cholera. In North America our conifer tree squirrels are larder hoarders that build and defend towers of cones. In the east there is the red squirrel, Tamiasciurus hudsonicus, the hoarding shade-tail of the Hudson, and in the Pacific Northwest the Douglas squirrel, T. douglasii. But if you see a tree squirrel in a city, it’s almost certainly a fox squirrel or an eastern gray.
Before 1840, cities were pretty much squirrelfree. The historian Etienne Benson has shown that it took painstaking effort to urbanize squirrels. City beautifiers released squirrels first in Philadelphia, then in Boston, and in New Haven, Connecticut. They provided the animals with food and nesting boxes. Children were encouraged to bring them nuts and cakes.
These days we generally discourage kids from feeding wild animals. We want our city wildlife to live parallel to us, never quite touching us. But back then, people wanted to civilize wildlife. Benson relates that George Perkins Marsh, often called the first American environmentalist, applauded the city squirrels, saying their tameness “was a foretaste of the rewards to be expected when man moderated his destructive behavior toward nature.” In other words, once Americans stopped conquering the land, we could settle down to live in harmony with the conquered. That harmony would look a lot like a city park full of gracious trees and squirrels that would eat out of your hand.
And eat they did: A report in 1865 declared that the squirrels in New Haven Green had “become so obese from good living that they are continually missing their hold and falling from the tree tops.” But despite all this effort to feed and house the rodents, the initial squirrel urbanization projects failed. The squirrels died; the environment just couldn’t support them. Presumably, after the initial enthusiasm for feeding squirrels wore off, obesity gave way to starvation. To move in and take over cities, squirrels needed an ally to reshape their landscapes. They found that ally in Frederick Law Olmsted.
Olmsted introduced the idea that cities should contain large tracts of idealized wilderness (his most famous design was New York’s Central Park). It was ideal for reading poetry in the shade or wandering with a friend, but mostly, it was ideal for being a squirrel.
In 1883, six years after sixty-eight squirrels were released in Central Park, it had an estimated population of 1,500. Olmsted is the acknowledged father of American landscape architecture, but it’s not as well recognized that he also is the father of city squirrels. City dwellers unwittingly contributed to the effort by lining the streets with trees and installing elevated squirrel transportation infrastructure in the form of telephone and electrical lines.
In the late 1800s, not everyone approved of Marsh’s vision of wilderness tamed. There were also those who said it was ludicrous to think that nature could ever be conquered and wanted to keep fighting it. This debate was personified on one side by Ernest Thompson Seton, who in 1910 helped start the Boy Scouts of America and wanted to befriend nature. On the other side was Theodore Roosevelt, who wanted to hunt down and kill nature. Both Roosevelt and Seton were fascinated with manliness, and they both believed that communion with wild animals was a crucial part of the mystical process that transformed boys into men of character. But their agreement ended there.
Seton thought squirrels would teach boys to be nurturing and empathetic. “Some day,” Seton wrote, “while a boy is feeding a squirrel, a dog may dash at it with evil design and the child will certainly and naturally try to save the squirrel that he was feeding, and thus cast in his lot with the squirrels against the dogs.”
This would plant a seed of empathy that would blossom into righteousness and chivalry. Seton wrote, “You can rely on work being done by these missionary squirrels whose influence will not end with the boundaries of the city park, but will continue to go as far as the boys go.”
Roosevelt thought squirrels, and all wild animals, were there to teach boys to learn courage. In his view, you’d start by killing spiders and beetles, move on to birds and squirrels, work your way up to bears, and before you know it you’d be a general like him. Ultimately, you’d need a war to truly become a man, and Roosevelt lamented that too much peace was emasculating the United States. Instead of teaching boys to protect squirrels so that they might later protect people, Roosevelt wanted boys to kill squirrels so they might later kill people.
Roosevelt attacked Seton for being a “nature faker,” and the slur stuck because it was true, at least in part. Seton sought to teach morality with animals, but to do this he took outrageous liberties in giving animals human qualities, populating his writing with heroic rabbits, crows that fly in military formation, and rams driven by dandyish pride.
But Roosevelt was just as much a faker. He constructed his macho persona from the ground up. When he first entered public life at the age of twenty-three as a New York state assemblyman, he was a rich kid with soft hands, a squeaky voice, and clothes that were a little too fashionable for his own good. The newspapers gave him nicknames: “Jane-Dandy,” “our own Oscar Wilde,” and “Punkin-Lily.” He went west to shake this reputation. Viewed from this angle, Roosevelt’s entire life looks like one gigantic exercise in overcompensation.
This argument between Roosevelt and Seton over nature and manhood had staying power. To this day, when people argue about saving endangered species or managing wildfires or responding to climate change, you can detect the ghosts of Roosevelt and Seton in the background.
I’ve spent a lot of time considering what lessons I want to pass on to my own kids. I grew up in the Seton mode: I understood that my moral development depended on protecting squirrels rather than shooting them. And yet, I wouldn’t want to pass on Seton’s ideology to Josephine, because it has so little grounding in reality. I’d also like to keep her away from Rooseveltian displays of masculine violence. Rather than conquering nature or giving it fake human morality, I’d want her to simply approach nature with open eyes and curiosity.
One of the benefits of writing about squirrels, as opposed to, say, wolves, is that—thanks to those nineteenth-century civic boosters—you can see them without any effort. There’s one squirrel that likes to eat the rose hips that hang over our wooden fence. It’s a fox squirrel, orange and white underneath and gray on his back. One morning he and I found ourselves face-to-face as I was taking my coffee grounds out to the compost pile. The squirrel was on top of the fence, at eye level about three feet away, gripping a rose hip in his mouth. There was what seemed like an insane intensity in his beady, close-set eyes. He regarded me with a cheeky lack of respect, then scrabbled forward and down onto the vertical face of the fence, all four legs spread. In this gravity-defying position, he traversed to the far end of my backyard.
I can’t help but see human emotions in squirrels. But I try not to go as far as Seton did—I refrain from making up motives and morals, and I strive to watch closely enough that my ideas might be shattered by something a squirrel does.
I don’t feel bad about anthropomorphizing my furry neighbor. That’s just how people work: We project our own expectations and ways of understanding the world onto the creatures around us, be they squirrels or family members. A few days earlier Josephine—at this point three years old, and a genius—had seen the same squirrel running along the same fence.
“Papa,” she said, pointing. “A cat!”
I do the same thing; I just don’t have someone around to correct me. We see what we expect to, what we have a name for, what pops immediately into our heads. But confirmation of the expected is boring, and false. Life only becomes interesting when you watch it closely enough to see something surprising, and with that surprise come a little closer to the real thing. That, I suppose, is the point of this book: to allow people to see past their expectations. When actual seeing pierces the skin of habituation, if only for a moment, it permits a bit of wonder to bleed through. Wonder is the animating ether that allows some lucky few to perceive not just the prosaic, but the most profound laws of the universe at work in the prosaic. I think that’s what the poet Philip Appleman was getting at in the prologue of Darwin’s Bestiary when he wrote:
The habit stays with us, albeit it’s puerile:
when Darwin saw squirrels, he saw more than Squirrel.
I think the hardest part of squirrel life, at least for the males, must be finding a mate. That’s because there are between five and twenty male squirrels for every female. Moreover, that one female is only receptive to males twice a year for a few hours at a time. The males go into a fevered mania during that breeding period, monitoring the females and then joining in daylong contests for their affections. Researchers have seen as many as thirty-three males participating in these competitions. These mating bouts look, Koprowski and Steele write, like “pure and unadulterated chaos.”
The males fight each other for position, often doing serious damage with their powerful incisors and sharp claws. The dominant male then advances on the female. But the female usually has her own ideas and sprints away. The males give chase in single file. If they lose track of her, mayhem descends. They dash back and forth across the female’s territory, chirping in what sounds like a high-pitched sneeze. They will chase, with amorous intent, anything that moves. Researchers have seen frenzied males pursue blue jays, rabbits, crows, and, once, a softball.
A female may initiate these chases for her own safety, because it’s dangerous to mate in front of a lust-crazed mob. Attackers disrupt 20 percent of mating attempts, sometimes knocking the pair out of the tree. Usually the female stops in a safe location (i.e., close to the ground) and mates with the first male to reach her after a chase. If she’s managed to outrun them all, she calls out until a male finds her. The male guards the female for about twenty minutes after mating, but then the maneuvers begin again, and the whole circus can recur several times before the end of the day.
The fall breeding season is hard on males. They come out the other side injured and skinny. As Steele and Koprowski write, “Nothing demonstrated this to us more graphically than when we watched a rather groggy adult male fox squirrel emerge in the early morning hours and fall dead to the ground. Upon conducting a necropsy of this individual, we observed that he had 14 wounds from other squirrels and no visible body fat stores. He died primarily of malnutrition.”
And yet, this sad specimen was a winner: He had copulated five times that breeding season.
Squirrel life isn’t always so competitive. They also cooperate. Eastern gray squirrels may live together in groups of two to nine, cuddling up in big leafy nests and grooming each other when they emerge in the morning. When it’s a group of females, they are usually related, and they keep coming back night after night—there’s an evolutionary benefit in taking care of someone when you share genes. The male groups aren’t as stable, but they are even more remarkable because they nest with compatriots that aren’t closely related. They are able to form alliances with other bachelors without the force of family.
The nests are properly called dreys. When Jo and I went looking for acorns we were looking down at first, searching the ground. But then, while under a big tree, I looked up. The leaves formed a thick layer of green around the farthest extent of the tree, but the interior stems of a coast live oak are bare. Looking up the trunk was like looking into the complicated mechanism of a massive green umbrella. I could clearly see a drey straddling two branches.
“Look, Josephine, do you want to see a squirrel house?”
She dropped the pinecone she’d been picking at and trotted over. “Where?”
I crouched next to her and pointed. “It looks like a big ball of leaves. See it?”
Jo laughed in her low, huffy chortle, which signifies deep satisfaction.
But even as I was pointing, I saw another, smaller drey, and then another, and another. Dreys are a perfect example of the unseen city: Even if you think you’ve never seen them before, you probably have—anywhere there are squirrels, there are dreys, hiding in plain sight. But they are easy to miss because they look so messy, like a mass of leaves lodged high in the tree. But masses of leaves don’t just lodge in trees. That takes intention.
Squirrels start by building a base of leafy forked branches, then pile twigs atop that until it’s at least a foot across. Then, according to squirrel researchers Monica Shorten and Frederick Barkalow Jr., they will “dive and wiggle into the middle of the heap, using hands and mouth to tug and bite, and, judging by what can be seen from a distance, the cavity is shaped by repeated body turns.”
After lining the interior with moss, leaves, shredded bark, and whatever else is handy, the squirrel has a waterproof home with an interior of about the size of a bocce ball, on average. Obviously the drey must be bigger for a larger group.
The entrance to a drey is always covered by leaves, but you can see squirrels coming or leaving if you are willing to spend some time waiting. Just before sunset is a good time to set up watch: That’s when they return to their homes. But unless you are up in the canopy, it’s hard to tell which squirrel is going into which drey. As we were looking up into the live oak’s branches, a squirrel materialized and clambered toward us.
“Does he live in that nest?” Jo asked.
I had no clue; he could have been lurking in the upper branches, so I answered with another question. “Maybe, but Josephine, how do you know it’s not a girl?”
“Because, Papa,” she said, laughing at my ignorance, “he’s not wearing earrings.”
Here’s how you determine the sex of a squirrel: Wait until it stands on its hind legs, and then look for nipples or testicles. Josephine was right about this particular squirrel—it was almost certainly a male, because it had no nipples. If you look closely, they are clearly visible, unless the female is less than a year old and hasn’t had babies yet. The males are trickier: They have pendulous scrotums, but they retract into their bodies during July and August, between mating seasons (in eastern gray squirrels).
Learning to recognize individuals is an important step in becoming a good field observer of squirrels, the researchers say, and learning to see which are males and females helps with that. Then you can begin to look for more subtle details, such as variations in color, patterns, or scars.
Individuals can also be identified by their behavior. The morning after we found the dreys, Josephine pointed out that our backyard squirrel had joined us for breakfast. It was perched on the fence a few feet from the dining room window, eating rose hips. I was sure it was the same squirrel, not because I could see any identifying marks, but because of the rose hips and his manner. Just as before, he was fervently unafraid. He continued shelling the pulp off the rose hips, then cracking the seeds inside, even when I opened the window and Josephine leaned out over the sill, not five feet away.
He returned the next day during breakfast, and the next. There was no doubt that it was the same squirrel. After finishing each rose hip he paused to wipe his short muzzle against the fence, first one side, then the other. He steadily depleted the supply of rose hips, clambering farther out into the hanging brambles to procure those he couldn’t reach from the fence. His movements were not particularly graceful. Twice I saw him fall, but he always caught himself immediately. Perhaps squirrels favor resilience over precision: Instead of calculating each movement like a rock climber, they just scramble forward and trust in their strong claws if a foothold fails.
After a week, there were no more easily accessible rose hips. There was one branch laden with red fruit, but it extended too precariously for our squirrel. He tested his weight on it and then retreated to eat the black rose hips of years past instead.
I picked one of the fresh rose hips to see what our squirrel was after. Inside were eleven slick seeds, each about the size and shape of a lemon seed. They were tremendously difficult to crack, and each time I succeeded in breaking through the husk with a knife, the pieces scattered across the kitchen. The black rose hips I picked contained only a couple of fat seeds, the rest being withered and thin. I picked a few of the fresh rose hips from the forbidden bough and left them along the top of the fence to see if our neighbor would take them, or if he now preferred the older vintage.
The next day my offering was reduced to bits. I replaced it with several more rose hips, but these remained untouched atop my fence. Another puzzle. The squirrels gave me a clue the next morning. Often, I’ll hear squirrels—their claws on bark, or a tumult of clattering branches—before I see them. As I sat on the stoop lacing my running shoes, I became aware that there were at least two squirrels in the oak tree across the street. One bounded directly at me, and when it reached my front yard I could see that it held an acorn in its mouth. Perhaps the acorns had ripened and rose hips were suddenly passé.
The squirrel buried the nut and I kept my gaze fixed on the tuft of grass that marked the spot. Koprowski and Steele had written that “ultimately, the squirrels’ decision of what to eat and what to cache may determine the structure, composition, and population biology of our oak forests.” I would add that it’s not only our forests, but also our yards, medians, and city parks. I’d noticed two small sprouts emerging from the earth beside our house, both of them coast live oaks, and I realized it was entirely possible that this very squirrel had planted them. There was news breaking in my neighborhood that was going unreported: news of the squirrels’ plans for the long-term development of the urban forest, news of acorns ripening and the relative size of the year’s crop, news of the way the replacement of the eastern grays by fox squirrels had changed the rhythms of these cycles within cycles. I could see just enough to see what I was missing. I crossed the sidewalk and resolutely excavated the turf where I’d seen the squirrel bury the acorn. It was nowhere to be found.