The skull of a woodpecker has long been thought to serve as a shock absorber that minimizes the harmful deceleration on its brain while pecking hard woods. Researchers at the University of Antwerp, Belgium recently used a Mikrotron EoSens TS3 camera to challenge this hypothesis.

Sept. 12, 2022 - In the scientific community, the skull of a woodpecker has long been thought to serve as a shock absorber that minimizes the harmful deceleration on its brain while pecking hard woods. This theory has inspired the engineering of products ranging from impact-absorbing foams to bike helmets, automobile shock absorbers, and airbags.   Researchers1 at the University of Antwerp, Belgium recently challenged this hypothesis based on the premise that any absorption or dissipation of kinetic energy by the skull would likely impair the bird’s hammering performance. If the prevailing theory held, in other words, the more shock a woodpecker's beak absorbed, the harder the bird would have to peck for the same result, therefore significantly reducing penetration of the beak into the tree.   University of Antwerp researchers used a Mikrotron EoSens TS3 camera in their efforts. This compact, versatile camera acquires images up to 500 frames-per-second (fps) at 1280 x 1024 resolution, or up to 20,000 fps at reduced resolutions, to help in the analysis of extremely fast-moving processes in science, biology, and sports movement analysis. The 7-inch touchscreen display on the back of the camera allows instant playback in the field.    To obtain the most representative sample, the researchers tested several woodpecker species on a variety of wood types at different camera speeds, angles and resolutions. First, high-speed videos of two Black Woodpeckers (Dryocopus martius) were recorded in an uncompressed 10-bit monochrome format while pecking on hardwood tree trunks. The first black woodpecker was recorded at 2698 fps at a resolution of 512 × 410 pixels, while the second was recorded at 4000 fps at 402 × 322 pixels. Next, two Great Spotted Woodpeckers (Dendrocopos major) were filmed at 3000 fps using the Mikrotron camera at 480 × 384 pixels resolution while pecking on a bamboo stick. Finally, pileated woodpeckers (Dryocopus pileatus) were recorded in uncompressed 32-bit color at 1600 fps at 1280 × 800 pixels during pecking on spruce beams. In all cases, shutter speeds were set to the inverse of the frame rate to eliminate motion blur.    A total of 109 videos were captured. To accurately perform frame-by-frame tracking of the movement of head and beak movements during and following impact, researchers tagged the video with anatomical landmarks on each bird's beak, its eye, and on the skin covering the skull posterior of the eye. Analysis was then performed using Didge 2.3 and XMAlab 1.5.5 software. Coordinates of the anatomical landmarks were continuously tracked approximately every 12 milliseconds. Applying the results of the video analysis, researchers built mathematical models of the penetration of each woodpecker's beak into the wood that were later simulated using Simscape Multibody from Mathworks.   Findings revealed that the heads of woodpeckers function as stiff hammers during pecking. Consequently, the zones of spongy bone at the sides of a woodpecker's braincase probably serve a role in “resisting” impact forces, rather than for “absorbing” impact energy by elastic deforming as has been long believed.   According to the researchers, the study's insights expose a long-standing misconception about the presence of shock absorption in woodpeckers which has infiltrated both common belief and scientific research. The study also opens up new avenues for research to help better understand the mechanics behind cranial stiffening during pecking in birds. For example, how do woodpeckers manage to achieve this high stiffness in their cranial system without concussions? How is the suspension of the lower beak fixed during pecking? The University of Antwerp researchers plan on continuing to pursue these questions in future work.

Mikrotron GmbH, established in 1976 and located just outside Munich, Germany, provides a full range of high-end imaging solutions for challenging applications in industry, engineering, science and sports. The company designs, produces, and commercializes high-speed and high-resolution cameras, image recording cameras and systems, software and image processing components. Mikrotron's slow-motion recording enables customers to optimize manufacturing processes, improve product design, revolutionize quality management and analyze motion. Mikrotron is ISO:9001 certified. Mikrotron is operated as a business unit of TKH Visions.

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