Olympic gymnasts amaze the world with their performances on the uneven bars. Fortunately, they don’t have to compete with squirrels.
Suppose that instead of the uneven bars, human gymnasts would have to fly through the treetops, jumping gaps of different distances, from branches of different thicknesses, some stiff, others bouncy. And every landing would be different, from trunks to branches.
Oh, and then there are the hawks to watch out for.
What Makes Squirrels So Good?
Cognitive scientists and biomechanics experts from the University of California, Berkeley, set out to test both the agility and decision-making of wild fox squirrels in a eucalyptus grove on the edge of campus. This is a different species from the common eastern gray squirrel, but both are experts at navigating the canopy of trees.
Not only did the researchers record the squirrels ‘jumping and landing, but they were also able to analyze the animals’ decisions about how and where to jump. In one part of the experiment, the animals invented parkour-like movements in the middle of a jump to hit a vertical wall and adjust their speed and distance, which messed up the original purpose of the test.
Lucia F. Jacobs, a cognitive psychologist who has studied extensively with squirrels and who was one of the authors of a report on the work in Science, said, “In some ways, this isn’t very surprising as a squirrel biologist. If we were to hold a Squirrel Olympics, it wouldn’t even be the qualifying meeting. “
But it was unusual for cognitive and biomechanical minds to come together to conduct a joint investigation.
Nathaniel H. Hunt, the lead author of the article, initiated the project as a PhD student and led the actual squirrel events with Judy Jinn, a student in Dr. Jacobs’ lab and co-author.
Dr. Hunt, now at the University of Nebraska, Omaha, said that many previous biomechanics studies focused solely on the structure and movement of animals, but this group wanted to understand decision making, learning, and creativity related to physical challenges.
Squirrels are a good choice because, in addition to their sportiness, they “also have a great ability to make decisions, solve puzzles and learn”.
Dr. Robert J. Full, a biomechanics expert and another writer, said the first question was how does the squirrel weigh the variables of distance and flexibility of a branch in making a jump. Going out to the end of a branch, where one branch is very flexible, can provide a very short jump to the next branch. But pliable branches don’t provide a solid platform bounce, so you can’t rely on using your muscles efficiently.
The squirrels (all wild, all free to come and go) were trained to jump on perches for a peanut reward. The team made various perches or artificial branches that looked the same from the outside, but had different spring forces along the length of the branch and between the branches.
The researchers found that the stiffness of the launching branch was most important to the squirrels. “They care more about a stable starting position, about six times more than they care about the height they have to jump,” said Dr. Full.
Squirrels also learned quickly when a stiff branch was replaced by a similar springy branch. And they never fell during exams, mainly because they made acrobatic landings: swinging under, swinging over, hanging on their front legs. All the maneuvers known to anyone who has ever tried to set up squirrel-proof bird feeders.
The researchers also changed the length of the jumps and the height of the takeoffs to see if practice and learning would increase some squirrels’ overall proficiency. But the squirrels only changed the way they jumped. “You decide to park by the wall and land on the pole,” said Dr. Full. They adjusted their jump in the middle and increased or decreased their speed.
The test subjects were definitely unimpressed by the new challenge, said Dr. Full. “They look at us like, ‘We’re squirrels …'”
David Hu, who studies animal movements at Georgia Tech, said he found the ingenuity of parkour movement interesting. “There should be more work like this – examining the animal creativity involved in accomplishing tasks that cannot be accomplished without innovation.”
He also loved the way the squirrels deal with mistakes. They are not perfect at all and often exceed or fall short of their target. But they can land anyway.
“Squirrels are used to making mistakes (the jumps are split-second decisions, after all),” he said in an email, “but they succeed because they are experts in correcting themselves when landing.”
“I think there is a moral for all of us,” added Dr. Hu added. “Don’t worry about a wrong jump, as long as you can relax like a squirrel you will be fine.”