Science News

Could you climb like Spider-Man?

Fri, 22nd Jan 2016

Felicity Bedford

Researchers this week have shown that Spiderman can't exist, unless he has SpidermanUK size 89 feet. 

In the animal kingdom lots of animals are capable of sticking to vertical surfaces and climbing to escape from predators or hunt.

For a human, like Spider-Man, to stick to a vertical surface they would require adhesive feet, taking advantage of weak molecular forces of attraction between their body surface and the wall, much like a gecko. 

Unfortunately, however, according to researchers at the University of Cambridge, Peter Parker would meet a tragic end as the ability to climb using sticky pads seems to be limited to animals with smaller body sizes.

Publishing in PNAS this week, David Labonte and colleagues looked across the animal kingdom to see if the species which have sticky pads have anything in common.

"There’s only a range of sizes that actually use sticky pads, so you find tiny mites, you find big geckos, you find frogs and spiders and many different insects in between," author David Labonte explains. 

The reason that larger animals, including humans, can't use sticky feet is because of the relationship between their body size and surface area. 

As animals get larger their volume increases rapidly. However, the equivalent surface area increases at a much slower rate. 

For a small creature, like an ant, which has a small volume, it can use a relatively small proportion of its surface area to support its weight and stick to a surface using its feet. 

Larger animals would need to use much more of their body as a sticky surface. To take this to extremes, it is difficult to imagine an elephant climbing using sticky feet!

Climbing animals maximise the surface area of their feet not only by making them larger but also by using arrays of microscopic hairs or cushions covering their foot pads. 

These structures are found across very different animal groups, which indicates this is an extremely effective strategy as it has evolved independently multiple times. 

Even using the complex structures found on sticky pads a real life Spider-Man would need to have UK size 89 feet in order to support the weight of a human sticking to a vertical surface.

But, the comic book hero might be able to try a different animal strategy to remain sky high.

"Larger animals also see the world in a different way," says David Labonte. "If you think of an ant, a twig is effectively flat for the ant, whereas if you think of a monkey, the monkey can grasp around the twig."

If you are a large animal, having appendages which can grasp and grip your environment is a much more sensible evolutionary strategy than giant sticky feet!

 

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