Male Spiders Are Attracted to Female Planets Orbiting a Star – ScienceDaily

The small male golden orb-weaving spider faces a major challenge when looking for a mate. It is a fraction of the size of the massive female, but must tread carefully and approach her without being noticed, as the cannibalistic female will kill and eat him if he makes one wrong move on her web. Add to this gamble the competition he faces from other men, including in the delicate arena of the web, and you have a complex optimization problem that even human analysts would find daunting. Yet these little spiders hardly have what we would recognize as brains. How do they arrange it then? This is a question that has fascinated Alex Jordan and members of his lab at the Max Planck Institute of Animal Behavior for more than a decade. Now that they are collaborating with researchers at the Weizmann Institute of Science, they are closer to an answer.

The solution seems to lie in animal magnetism, or rather, in the effective physical forces that males and females experience on the elastic surface of the spider’s web. “Our original concept was to explore the idea that these spiders moving on the web behave like electrons orbiting a nucleus, or planets orbiting a star,” said Jordan, who leads the Integrative Behavioral Ecology Lab at the Max Planck Institute of Animal Behavior, and is co-senior author of the study. From this initial idea arose a research program that led the two teams to develop a physical model and conduct experiments in the Panamanian rainforest.

Competitive Web Arena

Although the details of the precise physics eventually diverged from both atomic and cosmic levels, the concept proved useful. “Imagine electrons orbiting a nucleus or a massive star in space so large that it generates its own gravitational field and pulls objects around it — the gigantic, cannibalistic female can be seen the same way,” Jordan says. “Now imagine smaller planets, satellites or comets coming close to this attractive force – these are our little brave men.” Approach the star (or woman) too quickly, or at the wrong angle, and you risk getting caught up in her alluring appeal. On a cosmic scale, this will result in a cosmic collision that will vaporize the planet. For the intrepid male, a wrong approach means falling into a fatal attraction and ending up as prey.

“While working in the rainforests of Panama, I have often seen overzealous males fall victim to the cannibalistic females, especially when they take the wrong path or approach the female too quickly,” said Sylvia Garza, co-author of the study. who spent months in Panama as a master’s student recording the behavior of male and female spiders, then using machine learning approaches to track their every move.

Vibrating Signals

Just as the smaller planets have their own gravitational pull, the males also attract each other, initially approaching the observed rival. The males also begin to repel each other as they get closer, acting much more like electrons around a nucleus in this way.

“The movement of these males resembles interactions between particles that attract or repel each other, depending on the distance between them,” said Amir Haluts, a physicist by training and lead author of the study at the Weizmann Institute of Science. Co-senior author Nir Gov, also of the Weizmann, says: “We use models to map the effective physical forces experienced by men, allowing us to explain their movement on the web, as well as the competition dynamics of men of different sizes. ” As the males orbit each other, they will eventually get too close and bump into each other in open fights. All of this takes place on the surface of the web, which acts as a channel for the vibrations that males use to communicate, but can also alert the female to their presence and lead to a deadly attack.

The team’s research shows that the seemingly complex decisions men make, balancing risk and reward, life and death, do not require advanced intelligence or understanding of the game they are playing. Instead, the same solutions can be achieved by sensing vibrations on the web and responding to the physical forces of attraction and repulsion, just as physical particles might. “Early on, I was stunned by our initial results, which showed that these men could apparently solve these complex tasks without the required cognitive machines,” Jordan says. “I joked with Nir that it almost seems like these males are electrons orbiting the female ‘nucleus’. This led us to coin the term ‘Atomic Spiders’ and it turns out it might not be that far from the truth.”

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Materials supplied by Max Planck Society. Note: Content is editable for style and length.

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