Why Don’t Woodpeckers suffer TBI?

August 09, 2022, Kitchener, Ontario

Posted by: Robert Deutschmann, Personal Injury Lawyer

In humans TBI is caused most often by a blow to the head which ‘jiggles’ the brain resulting in damage to the brain tissue. So why don’t woodpeckers who seem to jack-hammer trees for their entire lives get brain damage? Can we learn from their physiology to better protect humans?

This publication from Smithsonian Magazine considers this exact questions. In short the researchers determined that the birds can withstand sudden brain/head movement much better due to their small size. Think about a fly. When it hits a window it simply bounces away and keeps flying.

In the woodpecker’s case, their brain is 700 times smaller than human brains. According to the models the birds would need to strike wood twice as hard as they do in order to injure themselves.

In this case, humans cannot adapt the woodpecker’s protection method.

You can read the entire study in Current Biology. Here is the summary of the report:

Woodpeckers minimize cranial absorption of shocks

Sam Van Wassenbergh, Erica J. Ortlieb, Maja Mielke, Christine Böhmer, Robert E. Shadwick, Anick Abourachid

Highlights

• Woodpecker heads behave very stiffly during in vivo pecking impacts
• Shock deceleration of the braincase is not reduced relative to the beak
• Absence of cranial shock absorption is adaptive to improve pecking performance
• Inertial loading of woodpecker brains is below primate concussion thresholds

Summary

The skull of a woodpecker is hypothesized to serve as a shock absorber that minimizes the harmful deceleration of its brain upon impact into trees and has inspired the engineering of shock-absorbing materials and tools, such as helmets.

However, this hypothesis remains paradoxical since any absorption or dissipation of the head’s kinetic energy by the skull would likely impair the bird’s hammering performance and is therefore unlikely to have evolved by natural selection. In vivo quantification of impact decelerations during pecking in three woodpecker species and biomechanical models now show that their cranial skeleton is used as a stiff hammer to enhance pecking performance, and not as a shock-absorbing system to protect the brain. Numerical simulations of the effect of braincase size and shape on intracranial pressure indicate that the woodpeckers’ brains are still safe below the threshold of concussions known for primate brains. These results contradict the currently prevailing conception of the adaptive evolution of cranial function in one of nature’s most spectacular behaviors.

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