We used peanuts and a climbing wall to learn how squirrels judge their leaps so successfully – and how their skills could inspire more nimble robots


We used peanuts and a climbing wall to find out how squirrels decide their leaps so efficiently – and the way their expertise may encourage extra nimble robots

How do they stick their landings? Alex Turton by way of Getty Photos

Tree squirrels are the Olympic divers of the rodent world, leaping gracefully amongst branches and buildings excessive above the bottom. And as with human divers, a squirrel’s success on this competitors requires each bodily energy and psychological adaptability.

The Jacobs lab research cognition in free-ranging fox squirrels on the Berkeley campus. Two species – the japanese grey squirrel (Sciurus carolinensis) and the fox squirrel (Sciurus niger) – thrive on campus landscapes and are keen members in our behavioral experiments. They’re additionally masters in two- and three-dimensional spatial orientation – utilizing sensory cues to maneuver by means of house.

Squirrel perches in a tree.
Fox squirrel in eucalyptus grove on the campus of the College of California, Berkeley.
Judy Jinn, CC BY-ND

In a newly revealed examine, we present that squirrels leap and land with out falling by making trade-offs between the space they should cowl and the springiness of their takeoff perch. This analysis offers new insights into the roles of decision-making, studying and conduct in difficult environments that we’re sharing with researchers of human motion and with engineers. At current, there isn’t a robotic as agile as a squirrel, and none that may be taught or make choices about dynamic duties in complicated environments – however our analysis suggests the sorts of skills that such robots would want.

Pondering on the go

Whereas a squirrel’s life might look easy to human observers – climb, eat, sleep, repeat – it entails finely tuned cognitive expertise. Squirrels are specialised seed dispersers: They harvest their winter’s provide of nuts and acorns throughout a six- to eight-week span within the fall, bury every nut individually and depend on spatial reminiscence to retrieve them, typically months later.

We all know that squirrels arrange their caches hierarchically. When supplied with 5 nut species in a random order, Berkeley fox squirrels buried nuts in clusters in response to species. As a result of bigger nuts comprise extra energy, squirrels make investments extra closely in them, carrying them to safer areas and spacing their hiding locations farther aside.

We additionally found that a squirrel assesses the worth of a nut by flicking its head with the nut in its mouth, simply as a human would possibly bob a pencil in her hand to evaluate its weight. And we all know that they create their cache maps based mostly on components that embrace the shortage of meals in that season, the amount of nuts already cached and the chance of being noticed caching by different squirrels.

Squirrel reaching down into a hole, head obscured.
Grey squirrel rummaging by means of its nut cache in late fall.
Mark Gunn/Flickr, CC BY

Together with observational research, we’ve got additionally assessed how squirrels carry out summary spatial duties. For instance, we’ve got measured how effectively they can inhibit a lunge towards a remembered meals location – a part of a world examine on the evolution of self management. In one other experiment, we put squirrels by means of a vertical maze that mimicked the branching choices they face when navigating in bushes to see how they return to areas that they bear in mind.

We even have discovered that whereas squirrels have been fixing a tabletop reminiscence puzzle, their cognitive flexibility peaked through the intense interval of storing their winter meals provide. This explains why Berkeley squirrels are capable of swap extra simply between sorts of landmarks through the caching season.

Going airborne

Our new examine introduced collectively squirrel psychologists and comparative biomechanists to ask whether or not squirrels’ cognitive decision-making extends to dynamic modifications in locomotion – the well-known squirrel leap. How do squirrels’ perceived capabilities of their our bodies and their guesses in regards to the stability of the atmosphere form their choices about motion?

Robert Full from the PolyPEDAL Laboratory is famend for research that extract basic design rules by means of experiments on locomotion in species with distinctive specializations for motion, from crabs to cockroaches to leaping lizards. Graduate college students Nathaniel Hunt, who’s skilled in biomechanics, and Judy Jinn, skilled in animal cognition, took on the problem of assessing how a leaping squirrel may reply to sudden modifications within the location and adaptability of experimental branches.

To review this query in wild squirrels, we designed a magnetic climbing wall that may very well be mounted on wheels and rolled out to the well-known Berkeley Eucalyptus grove to fulfill the squirrels on their very own turf. We introduced high-speed cameras and peanuts for persuading squirrels to patiently wait for his or her activate the wall.

Our aim was to steer squirrels to take off from a versatile springboard connected to the climbing wall and soar to a set perch protruding from the wall that held a shelled walnut reward. And as soon as once more, squirrels stunned us with their acrobatics and innovation.

Judy Jinn trains a fox squirrel on the Berkeley campus. Video by Nathaniel Hunt, UC Berkeley.

By growing the springiness of the springboard and the space between it and the aim, we may simulate the problem a squirrel faces because it races by means of tree branches that fluctuate in measurement, form and adaptability. Squirrels leaping throughout a niche should resolve the place to take off based mostly on a trade-off between department flexibility and the dimensions of the hole.

We discovered that squirrels ran farther alongside a stiff department, so they’d a shorter, simpler soar. In distinction, they took off with only a few steps from versatile branches, risking an extended leap.

Utilizing three branches differing in flexibility, we guessed the place of their takeoff by assuming equal danger for leaping from an unstable department and soar distance. We have been mistaken: Our mannequin confirmed that squirrels cared six instances extra a few steady takeoff place than how far they needed to soar.

Subsequent we had squirrels leap from a really stiff platform. Unbeknownst to the squirrels, we then substituted an identical-looking platform that was thrice extra versatile. From our high-speed video, we calculated how distant the middle of the squirrel’s physique was from the touchdown perch. This allowed us to to find out the touchdown error – how far the middle of the squirrel’s physique landed from the aim perch. Squirrels rapidly realized to leap from the very flexible department that they anticipated to be stiff and will stick the touchdown in simply 5 tries.

A fox squirrel studying to leap from a versatile platform. Video by Nathaniel Hunt, UC Berkeley.

Once we raised the ante nonetheless additional by elevating the peak and growing the space to the aim perch, the squirrels stunned us. They immediately adopted a novel resolution: parkour, actually bouncing off the climbing wall to regulate their pace and achieve a swish touchdown. As soon as extra, we found the outstanding agility that permits squirrels to evade predators in one among nature’s most difficult environments, the tree cover.

A fox squirrel parkours off a vertical floor to extend stability for touchdown. Video by Nathanial Hunt, UC Berkeley.

Thousands and thousands of individuals have watched squirrels resolve and raid “squirrel-proof” fowl feeders, both dwell of their yard or in documentaries and viral movies. Like Olympic divers, squirrels should be versatile each bodily and cognitively to succeed, making speedy error corrections on the fly and innovating new strikes.

With the funding this mission attracted, we’ve got joined a staff of roboticists, neuroscientists, materials scientists and mathematicians to extract design rules from squirrel leaps and landings. Our staff is even on the lookout for insights into mind operate by finding out leap planning in lab rats.

Our evaluation of squirrels’ outstanding feats can assist us perceive learn how to assist people who’ve strolling or greedy impairments. Furthermore, with our interdisciplinary staff of biologists and engineers, we try to create new supplies for probably the most clever, agile robotic ever constructed – one that may help in search-and-rescue efforts and quickly detect catastrophic environmental hazards, comparable to poisonous chemical releases.

A future imaginative and prescient for our efforts? First-responder robotic squirrels, geared up with the bodily and cognitive toughness and adaptability of a squirrel at a fowl feeder.

Judy Jinn, who participated on this examine as a graduate scholar, is a quantitative UX Researcher at Fb.

Lucia F. Jacobs receives funding from a Multi-College Analysis Initiative (MURI) from the Military Analysis Workplace (ARO).

Nathaniel Hunt receives funding from the Nationwide Institutes of Well being.

Robert J. Full receives funding from a Multi-College Analysis Initiative (MURI) from the Military Analysis Workplace (ARO).

The Conversation

This text appeared in The Dialog.

Lucia F. Jacobs

visitor writer

Lucia F. Jacobs is a Professor of Psychologya on the College of California, Berkeley

Nathaniel Hunt

visitor writer

Nathaniel Hunt is an Assistant Professor of Biomechanics on the College of Nebraska Omaha

Robert J. Full

visitor writer

Robert J. Full is a Professor of Integrative Biology on the College of California, Berkeley



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