The woodpecker spends the day beating the bark of trees with its small skull in search of food. However, he does not suffer brain damage. How is this possible? The explanation that had been given so far was that the animal has a series of spongy bones that absorb continuous impacts, preventing the brain from being destroyed. The muscles in your neck would also protect you. A new study published in Current Biology points rather to the reduced size of the brain as a protective element.
Woodpeckers can move their heads up to 20 times per second , experiencing forces of up to 1,400 g. Forces of only 90-100 g are needed to concussion a human being. If, in addition, we take into account how small the brain of this bird is, how does it not break like a walnut?
Previous research concluded that the woodpecker has a series of body adaptations that would help reduce the impact on brain tissue. We are talking about spongy bones and the muscles of the neck . These features appear to be designed to absorb shock, but it is less clear how they reduce the forces experienced by the bird’s head when rapidly accelerating and decelerating.
“By analyzing high-speed video of three species of woodpeckers, we found that they do not absorb the shock of impact with the tree,” says Sam Van Wassenbergh, a biomechanics researcher at the University of Antwerp, Belgium.
For the investigation, more than one hundred high-resolution videos were used in which six woodpeckers of the species Dryocopus martius , Dryocopus pileatus and Dendrocopos major were seen. The scientists looked at the birds’ eyes to measure the deceleration that occurred in them when hitting the trunk of a tree. Since the eyeball is a good substitute for the brain, the researchers calculated the physics of a decelerating skull. What they saw was that the little woodpecker’s head moves as a whole, with little variation of maximum deceleration between the eye and the bill. “Their heads basically function like stiff, solid hammers during pecking,” says Van Wassenbergh.
As for the bodily adaptations designed to absorb the impacts, the biomechanical models carried out by the scientists showed that they did not absorb much of the impacts between the tip of the beak and the brain, rather what they managed was not to fracture. By not breaking into a thousand pieces, the bird’s work is more efficient. “If the beak were to absorb much of its own impact, the unlucky bird would have to hit even harder,” the researchers explain.
An earlier study argues that a lifetime of headbanging takes its toll on woodpeckers. Van Wassenbergh and his team think otherwise. Based on their simulations of the intracranial pressure of the woodpecker, the researchers do not see the constant blows as serious because the brain is small .
“The absence of shock absorption does not mean that their brains are in danger during seemingly violent impacts,” says Van Wassenbergh. “Even the strongest shocks of the more than 100 pecks that were analyzed should still be safe for woodpecker brains, as our calculations showed brain loads lower than those of concussed humans.”
These findings would be key to understanding why woodpeckers didn’t evolve to be larger. Although at first you might think that the bigger, the more power to hit and find food, a heavier brain could not withstand the pressure and would fracture.
Referencia: Van Wassenbergh, S. et al. 2022. Woodpeckers minimize cranial absorption of shocks. Current Biology. DOI: https://doi.org/10.1016/j.cub.2022.05.052
