Friday, December 3

Scientists wanted to understand how a squirrel jumps. And he surprised them doing ‘parkour’ | Science


Filmmaker Alfred Hitchcock used to say that you shouldn’t work with children or animals (or with Charles Laughton); the result was too unpredictable. The same is true of experiments carried out by scientists, as the group trying to understand how squirrels jump can show. This team of researchers challenged the rodents to test their ability to jump, trying to get them to fail. Not only did they not fall, but they innovated with pirouettes of parkourdeciphering the evidence in ways so surprising that they have deserved their achievements to be they publish in the magazine Science. Along with their superb strength and agility, it is their intelligence that enables them to examine, learn, and decide successfully.

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To simulate the natural difficulties of trees, the scientific team led by Lucia Jacobs, from the University of California at Berkeley, placed the squirrels on flexible branches that did not allow the naked eye to identify their resistance. Some firmer, others softer, the squirrel had to find the ideal point to jump from the false twig to the prize of its target. Closer to the base of the branch gives more consistency to the jump, but forces fly further away; closer to the target gives less momentum stability. The squirrels preferred the first option and to ensure greater firmness under their feet when propelling themselves. The scientists moved the target on which the animal was to land, to observe how it modulated its response to the changing challenge. And then the surprise came.

“It was a total surprise: our squirrels on the Berkeley wooded campus had no prior experience with a vertical surface.”

Lucia Jacobs, University of California at Berkeley

“Unexpectedly, the squirrels perceived the vertical surface of the device as an additional possibility,” explains the study. They used an innovative strategy: instead of jumping directly from branch to branch, they incorporated the vertical wall that held them in order to perform “a maneuvering maneuver against it. parkour”, The street sport that consists of taking advantage of urban architecture to move around with jumps and capers.

Jacobs acknowledges by email that they were not expecting it: “It was a total surprise: our squirrels, born and raised on the wooded campus of Berkeley, had no previous experience with a flat vertical surface placed near a branch” and had never observed a squirrel using the tree trunk in this way. “Therefore”, deduces this specialist in animal cognition, “we interpret this as another example of selective pressure for innovation in trees in this species, which has adapted so well to living in diverse habitats, for example urban ones.”

A squirrel jumps against the vertical wall to complete the jump with greater control over speed.
A squirrel jumps against the vertical wall to complete the jump with greater control over speed.Nate Hunt, UC Berkeley

The trap with which they overcame the challenge was a test of their intelligence. “Despite our best efforts, the squirrels never fell because they adapted very quickly to any disturbance. This included adding a movement of parkour when we increased the vertical height of the target: the squirrels bounced off the climbing wall, to control their speed and land precisely on the target, ”explains Jacobs. With this maneuver, they redirected their momentum, generating forces that allowed their speed and trajectory to be modulated. “His performance thus demonstrates the importance of cognition in physical performance in a wild animal under semi-natural conditions”, concludes the neuroscientist.

This is the first study to study how squirrels learn to jump, and the importance of doing so is due, according to Jacobs, to their ability to overcome sudden challenges in the environment. East superpower The squirrels to go from branch to branch through the trees at high speeds in an unstable and changing scenario must have arisen from strong pressure by natural selection, since squirrels must escape the attacks of raptors in that context.

The superpower of squirrels to go from branch to branch at high speeds arises from natural selection: it serves to avoid raptors and to mate

“It’s probably also determined by sexual selection: male squirrels compete with each other for access to females during intense mating chases, which last for hours,” adds Jacobs. The female mates with the winners of that race, so the males must run fast and jump accurately through the foliage. “This is the only time I have seen an adult male squirrel fall to a significant height from a tree when participating in this competition,” says the Berkeley expert. During the experiment, the squirrels did all kinds of pirouettes in the air or when landing on the branch, hanging by the hind legs, but they were always able to avoid falling.

As described in the study, carried out by Nathaniel Hunt, “The synergy between the biomechanical energy management and the information learned for the jump and the landing probably determines the way of jumping and the way through the foliage”. That learning is the piece they want to fit in now, a part of the study that was interrupted by the pandemic: how they learn to jump as young. “We hope it is due to an instinct to learn, the motivation to jump shaped by constant learning from trial and error,” says Jacobs.

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