"Take a deep dive into the world of these surprisingly brainy, aerodynamic, nut-crazed critters" by Katherine J. Wu

 

There are a lot of weird squirrel stories floating around out there. These nut-crazed little critters have been spotted canoodling car engines and casually snacking on discarded egg rolls. There’s little squirrels won’t sink their teeth into—and their taste for electrical wiring has infamously triggered citywide power outages. Squirrels have even sparked an international rivalry through the color of their fur alone: For years, five North American towns have been vying to be hailed as the “White Squirrel Capital of the World” (the title is supposedly held by Olney, Illinois). But that shortlist of shenanigans is just the tip of the bushy-tailed iceberg. Here are six stupendous snippets of squirrel science to help you celebrate squirrels today and every day.

1. Tree squirrels might give investment bankers a run for their money.

The moment a squirrel first encounters a tasty morsel of food, it has to make an important decision: Is it better to eat this now, or will it be more valuable in the future? A lot goes into answering that question, says Amanda Robin, who studies squirrel behavior at the University of California, Los Angeles.

Depending on the season, food might be scarce, making the prospect of a little nosh extra appealing. The nut itself could be highly perishable, and not worth a laborious dig. Or there could be lurkers nearby, waiting to poach a hastily buried treat. Many squirrel species make a ritual out of hoarding snacks—not unlike us humans. These rodents may not be ticking items off a grocery list or stashing leftovers in a refrigerator, but their food-storing strategies are no less sophisticated.

Recent work from a research group led by Lucia Jacobs, a behavioral biologist and squirrel expert at the University of California, has shown that fox squirrels (Sciurus niger), arboreal squirrels native to the eastern half of North America, will cache anywhere from 3,000 to 10,000 nuts each year. And the stockpiling isn’t done willy-nilly: The squirrels meticulously categorize their treats by source, variety, quality, and even preference as they bury them in various locales.

“Even if you give squirrels a random series of nuts, they will put the almonds here, but the hazelnuts there,” Jacobs says. This technique, called “chunking,” essentially bins important bits of information into manageable blocks, and is thought to help squirrels keep track of their yearly inventory. It’s the same mnemonic device that makes a phone number easier to remember when it’s written out as 867-5309 rather than 8675309.

And that’s only part of the squirrel sorting scheme: When they chance upon larger, more valuable nuts, squirrels will also venture farther from foraging sites before settling down to dig. The idea is that more far-flung locales might be tougher for competitor squirrels to find and pillage. Jacobs likens the process to investment banking, with each new find triggering a fresh round of caching calculus. The more precious a food item, the more important it is to stow it away with care. In other words: have nut, will travel. “These are economic decisions,” Jacobs says. “They just want to minimize that risk-return ratio.”

2. With so many nuts to keep track of, squirrels need astoundingly good memories—and oh, do they deliver.

Once a squirrel learns a trick, it won’t hesitate to use it again and again. It’s a lesson learned the hard way by certain homeowners, who pray in vain that the next screen door or bird feeder won’t be torn to shreds.

In 2017, Pizza Ka Yee Chow, a squirrel researcher at Hokkaido University in Japan, put this mental longevity to the test with a group (or scurry) of eastern gray squirrels (Sciurus carolinensis), which are native to the eastern half of the United States and southeastern pockets of Canada. Chow presented her squirrels with a tricky task: pressing levers to access big, juicy hazelnuts. The critters quickly finagled their way through, and Chow took the puzzle away. But even after nearly two years had passed, the same squirrels, which hadn’t seen the contraption in the interim, still knew how to nab the nuts.

They even proved handy when offered a modified puzzle that also relied on levers, but looked completely different. After a brief moment of hesitation, the squirrels realized that even with this new challenge, the same logic applied. Considering that 10 years old is a ripe old age for your garden-variety tree squirrel, a 22-month memory ain’t too shabby. “Their memory is just excellent,” Chow says. “It’s really amazing.”

3. Squirrels are marvelously mischievous.

Stop a dog on the street, and chances are it has a bone to pick with a squirrel. These critters are known to tease and deceive—and their penchant for mischief truly knows no bounds. Many of Chow’s experiments have been at least partially foiled by roving bands of squirrel saboteurs. “They’ve bitten off the screws and nails on our puzzle boxes,” she says. “And they’ve destroyed some of our cameras: They’ll bite off all the buttons… and then I have to use a pencil to get at the start and stop record buttons.” And, Chow adds, as the squirrels fiddle with the equipment, they end up taking a lot of selfies. That last one sounds funny—but those glamour shots can get in the way of recording real data.

Even amongst their own kind, squirrels are master manipulators. When eastern gray squirrels forage in the presence of others, they’ll sometimes engage in what’s called deceptive caching: If it senses a hungry interloper, a squirrel will fake the act of burying a seed, all the while keeping the true prize tucked away in its mouth. A squirrel can get pretty elaborate with the ruse, making a big show of packing the hole with soil and leaf material, before bounding off to deposit the actual seed elsewhere. The second squirrel, of course, raids the decoy only to be disappointed. “Up until the point where we found it in squirrels, this kind of tactical deception was thought to only occur in primates,” says Michael Steele, an evolutionary biologist and squirrel expert at Wilkes University. “To discover it in [what people consider] a lowly rodent was pretty exciting.”

According to Chow, squirrels are so clever that, in theory, we could probably get these tiny titans of trickery to use their powers for good (à la these trained crows that are solving France’s litter problem one theme park at a time). But that doesn’t mean we’ll necessarily be seeing recycling rodents in our near future. “They’re so impatient,” Chow says with a laugh. “They’re just like, ‘Give me the nuts!!’”

4. Squirrel speak is all kinds of complicated.

Squirrel chatter might sound like a blur of nonsense, but that couldn’t be farther from the truth. Within that fast-paced gobbledygook is actually an intricate repertoire of vocalizations that—depending on the species—might involve anything from come-hither calls to signaling the presence of a predator.

Even arboreal squirrels, which tend to be fairly solitary creatures, will still raise the alarm when threatened by a passing hawk or a particularly ornery dog. And many of these sounds have impossibly delightful, onomatopoeic names: The “kuk” is short, low, and repetitive—the standard scolding you’d get from a disgruntled squirrel that’s recently been driven up a tree. The “quaa” is higher and more protracted, while the third sound, the moan, is even shriller and more ululating.

And it seems squirrel body language is just as important. These rodents’ fluffiest appendages often offer the most tell-tail signs of danger. Two common tail movements are the twitch—which looks something like a shudder—and the flag, which engages the tail in a rhythmic whipping motion, almost like a revolving dough hook. Combined with a stern flick of the tail, a reproachful chitter from a squirrel might portend the approach of one type of predator over another. Scientists are still hard at work deciphering the squirrelly code—but while some progress has been made, much of the jargon has proved a tough nut to crack. Say quaat?

5. Squirrel sashays and shimmies could someday inspire new-and-improved search and rescue technology.

Though not all squirrels are entirely aerodynamic, for those that live amongst the trees, their day-to-day movements can put the best Cirque du Soleil shows to shame. “They’re so agile, leaping from tree to tree,” Chow says. “They’re like little monkeys.” Chow recalls seeing a tree squirrel on one of her first trips to England and being struck by its agility and flexibility. “The squirrel was very goal-oriented,” she says. “It made me want to understand how they maneuver in this world.”

They may pale in comparison to their flying squirrel relatives, but even tree squirrels are equipped with extraordinary anatomical adaptations that enable them to clear ten-foot gaps between branches and stabilize on uneven surfaces. Gray squirrels’ hind legs, for instance, are exceptionally powerful, packed with muscles that can propel their light bodies forward over large distances. They’re also equipped with hyper-mobile ankles, allowing them to rotate their paws and grip onto surfaces in nearly any orientation. “Their ability to navigate through trees and balance so well is kind of a superpower,” Robin, the UCLA researcher, says. “At least, it’s one that I don’t have.”

These aerodynamic feats are reason enough to give squirrels their due. But a team of researchers led by Robert Full at the University of California, Berkeley is putting their appreciation to work in pursuit of even loftier goals. By studying how squirrels move through space, Full and his colleagues are figuring out how to build bio-inspired robots that might power the search and rescue operations of the future.

                                             A Squirrel I Call Rocky

6. Sometimes, it seems like squirrels are everywhere. You’re not wrong (unless you’re in Antarctica).

To date, there have been nearly 300 species of squirrels discovered worldwide. And these globe-trotting goobers come in all shapes and sizes, ranging from the aptly named African pygmy squirrel (Myosciurus pumilio), which runs just five inches from nose to tail, to the glorious, technicolor Malabar giant squirrel (Ratufa indica), whose three-foot-long body can be seen soaring through the lush green canopies of Indian forests.

These raucous rodents are native to every continent, with the notable exceptions of Antarctica and Australia (though due to the deliberate introduction of two species in the late 19th and early 20th century, the outback is technically no longer squirrel-free). But travel far back enough along the squirrel family tree, and you’ll find that squirrels appear to have originated in just one place: North America. “They evolved here—they’re ours,” Jacobs, the UC Berkeley behavioral biologist, says. “Then they spread all over the world.”

For better or worse, squirrels are here to stay. You don’t get to be one of the most successful invasive species on the planet without some serious know-how… or without stepping on a few toes along the way. At the end of the day, though, whether squirrels have wriggled their way into your bird feeder or your heart, they’re worthy of respect—grudging though it might sometimes be.

-Katherine J. Wu

“Six Stupendous Reasons to Appreciate the Heck Out of Squirrels: Take a deep dive into the world of these surprisingly brainy, aerodynamic, nut-crazed critters”

PBS/Nova

 

                                             My Squirrel-Proof Bird Feeder