New high-speed videos show squirrels performing daring, parkour-like stunts — all in pursuit of peanuts.
In a new study, published Thursday (Aug. 5) in the journal Science, researchers at the University of California, Berkeley tested the agility of fox squirrels (Sciurus niger) on the university campus. Their goal was to learn how the squirrels maneuver through the tree canopy, bounding between branches of different sizes while consistently sticking the landing.
To recruit their bushy-tailed study subjects, the research team ventured into their campus eucalyptus grove armed with peanuts and a squirrel-size apparatus with fixtures for the animals to climb over. The apparatus could be fitted with different rods, meant to simulate tree branches, for the squirrels to leap from. On the other end of the apparatus was a landing perch with an enticing cup of peanuts stuck to its end. The squirrels quickly learned to leap from the rod to the landing perch in order to reach the peanuts, and the researchers adjusted the distance between the rod and the perch, to give the rodents a challenge.
When faced with rods of varying bendiness and gaps of different widths, the squirrels quickly adapted their leaping strategy, the team found. "When they leap across a gap, they decide where to take off based on a tradeoff between branch flexibility and the size of the gap they must leap," first author Nathaniel Hunt, who was a doctoral student at Berkeley during the study, said in a statement. (Hunt is now an assistant professor of biomechanics at the University of Nebraska, Omaha.)
For instance, when launching from a relatively stiff rod, the squirrels started their leap closer to the end of the rod, to minimize their jumping distance to the peanuts. But when launching from a bendy rod that curved under their weight, the squirrels began their leap sooner, presumably to take off from the sturdiest point on the "branch" and reduce the bending motion.
When leaping across a wide gap, the squirrels sometimes under- or overshot their jumps, but none ever fell, the authors noted in their report. "If they miss, they don't hit their center of mass right on the landing perch; they're amazing at being able to grab onto it," Hunt said in the statement. "They'll swing underneath; they'll swing over the top. They just don't fall."
But when faced with a really huge gap — measuring roughly three to five squirrels long — the rodents took an "unexpected" approach, the authors wrote. The squirrels used the back of the climbing apparatus — a flat, vertical wall — to execute an impressive parkour move, wherein they ricocheted off the wall and quickly reoriented their bodies to land squarely on the peanut perch.
Not only does the new study highlight the remarkable athleticism of squirrels, but someday, the data could be used to design agile robots, according to the statement. Several authors on the paper belong to a consortium funded by the U.S. Army Research Office, and their collective goal is to create the world's first robot with squirrel-like capabilities. Such a robot would be able to make split-second judgments to move nimbly through its environment — just like a squirrel does as it leaps across tree branches.
Originally published on Live Science.