The contemplative pleasures of getting to know my natural neighbors is a middle-class luxury. I don’t think I’d be taking the time to learn and taste my weeds if I was a single parent hustling to get my kids fed and into bed. I might, however, have the time if I were a child of that single parent—like Gibbons. There’s often at least one person in a household who could make time to forage if they knew how, or had a good mentor.
There’s a sense of satisfaction that comes with finding food to help support your family. I’m not talking like a survivalist here; there’s no way people in West Oakland are going to get the bulk of their calories from weeds anytime soon. I’m just pointing out that a small helping of foraged greens each day could make people healthier, even if it’s layered on a fast-food hamburger to provide some crunch.
There are many evangelical books, usually based on little science, extolling the healing benefits of wild plants. There’s no need to make airy claims about the superpowers of plants when we can instead point to the well-established benefits of eating leafy green vegetables. We’d all be healthier, poor and middle class alike, if we could open our eyes to the natural world around us and see the richness there that we usually miss. If by foraging we simply hope to harvest a little pleasure and a connection to the wild, the chances of success are good. But the likelihood of success declines if we’re primarily gathering food for the body rather than the soul.
Can we harvest our way to health, equality, and justice from the wild things around us? Not with weeds alone. That would require concerted political action. But we’d be well served by foraging among the weeds for symbols to fuel that action. The garden the Obamas dug into the White House lawn became a symbol of the struggle to get fresh, healthy foods into the hands of ordinary Americans. I’m a supporter of gardens in general, and of that garden specifically. But I’d like to point out that it was preceded by other symbols on the White House lawn. Once, many years before anyone knew the name Obama, Euell Gibbons put his arm through the fence surrounding the White House to pick four different edible plants. The food is there, and so are the symbols, if we have eyes to see them.
SQUIRREL
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.
SQUIRRELS AND TREES
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 f
ellow 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?
Memory
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, some
times 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.
Squirrels versus Trees
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.
Unseen City Page 6