A Natural Stress Deflector on the Head? Mechanical and Functional Evaluation of the Woodpecker Skull Bones

Abstract

The brain is one of the most important and complicated organs, but it is delicate and therefore needs to be protected from external forces. This makes the pecking behavior of the Woodpecker so impressive, as they are not known to sustain any brain injury due to their anatomical adaptations (a specialized beak, skull bone, and hyoid bone). However, the relationship between the morphology of the woodpecker head and its mechanical function against damage from daily pecking habits remain an open question. Aided by recent technical advancements, these questions can be explored by applying new materials science concepts of bioinspiration and This article is protected by copyright. All rights reserved.3 bioexploration to identify adapted structures/materials in a design that results from millions years of evolution. Two main features, including the beam-like bar structure of the jugal bone acting as a main stress deflector and the high natural frequency of the skull bone of woodpeckers can teach two lessons for potential materials development as well as engineering applications: protection of a delicate internal organ occurs by redirection of the main stress pathway and a large mismatch of the natural frequencies between the skull and brain avoids resonance and reduces the overall load experienced by the brain.

Multiscale Toughening Mechanisms in Biological Materials and Bioinspired Designs

“…The keel feature of Aristotle's lantern was modeled and found to contribute to the resilience of the sea urchin tooth. The impact resistance through stress deflection in the woodpecker skull was explored by placing a 3D printed woodpecker skull in a drop tower apparatus shown in Figure a,b) . The influence of a structural feature known as the frontal overhang was investigated by producing two types of additively manufactured prototypes: one with the frontal overhang present and one without.…”

“…Copyright 2015, American Association for the Advancement of Science. b) Reproduced with permission . Copyright 2019, Wiley‐VCH.…”

Woodpeckers minimize cranial absorption of shocks

“…Since the lifestyle of woodpeckers inevitably subjects these birds to high decelerations of the head, 20 multiple studies have sought adaptations related to shock absorption within the cranial musculoskeletal system of woodpeckers. [1][2][3]12,23 The spongy bone in a woodpecker's skull, which is particularly well developed at the frontal region of the skull just posterior to the naso-frontal joint between the upper beak and the braincase (Figure 1), has been identified as a prime candidate for shock absorption. 10,12,13 Impact energy could also be absorbed through eccentric or isometric contraction of the protractor muscles of the quadrate and lower beak (e.g., musculus protractor pterygoidei) if the lower beak is pushed posteriorly relative to the skull when impacting a tree.…”

“…This is explained by the demonstrated lack of adaptive value of evolving a built-in shock absorber (Figures 3C and S4C). Consequently, the zones of spongy bone at both the coup and contrecoup side of the braincase (Figure 1) probably serves an important role in ''resisting'' impact forces without failing 23,28 rather than ''absorbing'' impact energy by elastic deforming.…”

Implementing Fabrication as a Pedagogical Tool in Vertebrate Anatomy Courses: Motivation, Inclusion, and Lessons

“…2 ). A student athlete built a novel football helmet inspired by woodpecker skull anatomy and the shock-absorbing features of its morphology (e.g., Jung et al 2019 ). Kangaroos are a popular structure–function choice and one student taught themselves to use Fusion 360 software to design a digital model of the hindlimb ( Fig.…”