Woodpecker Bodies Cushion Collision Impact On Bird Brains
(Inside Science) -- Woodpeckers are some of the most industrious birds in nature. Their intense tapping -- all an elaborate effort to procure food -- can happen as rapidly as 20 pecks per second, with each strike transmitting a seemingly brain-rattling force of up to 1,200 times the force of gravity at Earth's surface.
Yet, despite those repetitive impacts, woodpeckers typically show none of the typical signs of head trauma. How do their brains endure this?
Their remarkable ability to absorb shock has made woodpeckers a favorite species to study for biology-inspired materials and design. Now, a new analysis shows that the bird's body stores most of the energy created in the pecking – and the understanding could lead to better helmets, cars or armor.
Wu Chengwei, a mechanical engineer at Dalian University of Technology in northeastern China, used CT scans of the birds' bodies to create a precise 3D model of the creature. Working with colleagues, he ran computer models and found that 99.7 percent of the energy generated in pecking was stored in the form of strain energy, which spread out the force over the bird's body. Only a tiny leftover fraction of the energy went into the bird's brain.
Beyond the obvious direct impact, there are other consequences of pecking at a tree. The repeated effort heats up the woodpeckers' heads. This is part of why they often take an interval of rest between bursts of furious tapping.
"The very special structure of the skull and the interval pecking method (for the heat dissipation) of the woodpecker is the key for [its] safe pecking," wrote Chengwei in an email to Inside Science. He added that he was inspired by speaking to a brain surgeon friend about the fragility of human brains. The results of the study were published in the journal Science China Technological Sciences in June.
Other researchers believe that woodpeckers have the right stuff for better materials. In 2011, two University of California, Berkeley engineers proposed a shock-absorbing system to protect tiny commercial devices from unwanted rattling and jiggling, inspired from a spongy bone contained within a woodpecker's skull.
Lakiesha Williams, an assistant professor of agriculture and biological engineering at Mississippi State University in Starkville, also studies woodpeckers, beginning after a student asked about them when working on a project about football helmets. Williams said that the new research is a good start in the right direction -- but she believes the analysis should have separated the beak into its three component parts -- keratin, bone and foam. The beak's outer layer is comprised of tiny scales of the protein keratin. The middle layer is a foamy material, and the inner layer is dense bone, which guides the concussive jolts toward the bird's body.
"Each of these parts [plays] a unique role in mitigation," she said.
Researching woodpeckers can be challenging, especially when it comes to obtaining enough material from specimens to dissect and analyze.
"We usually have to obtain them from the wildlife department, if someone there picks one up and stores it in the freezer," explained Williams. "They've been hard to come by and they're so small -- these beaks are a couple centimeters long so we really have to optimize our use."
Though the woodpecker packs a punch, it's not particularly bulky -- the biggest types weigh in at less than a pound.
"We tend to think stronger, tougher materials will always be better, but from an engineering view, they're usually heavy and costly to create," she said, adding that woodpeckers are able to maintain a large force with a small mass.
The applications of woodpecker understanding go beyond football helmets.
"What about vehicular design?" said Williams. "We may not use the exact components - foam, bone, and keratin -- to design cars, but what about the architecture of the beak?"
Chengwei pointed out that woodpecker-inspired materials have more applications, like an anti-shock car bumper on automobiles, or shock-proof space suits for astronauts.
Williams said that because woodpecker beaks strike wood at a lightning-fast 6-7 meters per second, the tech could also be applied to soldier armor, helmets, and military vehicles -- which all must be designed to absorb flying bits of shrapnel with similar velocities.
"Nature does it best when it comes to optimizing resources," she said.