How woodpecker avoids brain injury?

Abstract

It has long been recognized that woodpecker is an excellent anti-shock organism, as its head and brain can bear high deceleration up to 1500 g under fast pecking. To investigate the mechanism of brain protection of woodpecker, we built a finite element model of a whole woodpecker using computed topography scanning technique and geometry modeling. Numerical results show that the periodical changing Young's modulus around the skull affects the stress wave propagation in head and makes the stress lowest at the position of the brain. Modal analysis reveals the application of pre-tension force to the hyoid bone can increase the natural frequency of woodpecker's head. The large gap between the natural and working frequencies enable the woodpecker to effectively protect its brain from the resonance injury. Energy analyses indicate the majority of the impact energy (99.7%) is stored in the bulk of body and is utilized in the next pecking. There is only a small fraction of it enters into the head (0.3%). The whole body of the woodpecker gets involved in the energy conversion and forms an efficient anti-shock protection system for the brain.