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Woodpeckers and concussion
A woodpecker hammers its beak into the limb of a tree to search for insects to eat, to create storage space, or to audibly advertise for a mate. During the impact, the rate at which the head slows is about 1000g’s (1000 times gravitational acceleration). Such a deceleration rate would be fatal to a human or at best severely damage the brain and leave the person with a concussion. Why then doesn’t a woodpecker fall from a tree either dead or unconscious every time it slams its beak into the tree?
The ability of a woodpecker to withstand the huge deceleration when it hammers at a tree limb is not well understood, but there are two main arguments. (1) The woodpecker’s motion is almost along a straight line. Some researchers believe that concussion can occur in humans and animals when the head is rapidly rotated around the neck (and brainstem), but that it is less likely in straight-line motion. (2) The woodpecker’s brain is attached so well to the skull that there is little residual movement or oscillation of the brain just after the impact and no chance for the tissue connecting the skull and brain to tear.