The braincase of a skull may well be,as advertised,a strongly built and cleverly engineered structure,but listening to all that incessant banging coming from the direction of the crab apple tree in the garden,one has to wonder: Is it really strong enough to keep a woodpecker from having the most terrible headache?
And what about those rams you see butting heads with such determined ferocity? The crashing sounds,the visions of extreme violence,the frequent tangling of hornshow do animals with an instinctive need for such brutish behaviour prevent their brains from turning into rice pudding?
Some answers are to be found in the upstairs bedroom of a decidedly unremarkable suburban house on the outskirts of the city of Coventry,in the English Midlands. This is where a collector named Alan Dudley has spent the last four decades bent to a curious obsession. By day he works selecting veneers for gluing to the dashboards of expensive automobiles. After work,he collects skulls.
He now has thousands,from the great hulk of a hippopotamus skull to the tiniest and most delicate tissue-like skull of a wren,and his collection makes up one of the finest and most comprehensive known. Included in it are many skulls of creatures that do strangely violent things to their headsthe ram and the woodpecker among them.
Both creatures happen to have very dense skulls,especially in that rounded rear area known as the braincase,where they are built like armoured cars. Crucially,their braincases are also unusually smooth inside.
The brains of most animals that are prone to head banging these include deer and other antlered mammals,as well as various birdsare relatively small and smooth-surfaced; and theyre bathed in only small amounts of cerebrospinal fluid,leaving little room for the brain to move and be shocked by the sudden decelerations and accelerations of their weaponised heads.
Moreover,both rams and woodpeckers are scrupulous in the precise fashion in which they smash their heads into things,whether trees or one another: The aim is such that theres very little side-to-side torsion exerted on the brain,none of the movement that induces whiplash injury and other kinds of damage.
Gannets have solved a similar problem. These magnificent seabirds,with wingspans of as much as 6 feet,catch fish by spectacular dives into the ocean. Starting from heights of 100 feet or more,they enter the water at 60 mph and hurtle downward far beneath the surface,pursuing their chosen fish underwater using their wings to swim.
It’s an awesome performance not least because they are so successful as hunters: They are eagle-eyed and they have true binocular vision,which helps them lock on target. However,their fishing success is one thing. Their survival is quite another. To dive into water from 100 feet may not be lethal for a gannet,but it would,or should,get a fearful migraine. Yet that doesnt seem to happen. Gannets manage to bob to the surface with all their mental faculties intact,their brains entirely unhurt.
And how? Skull modifications,just as with the ram and the woodpecker. In this case,to mitigate the brain-shattering trauma of the collision with a wall of water,air sacs built into the gannets face act as cushion; its extremely long and narrow beak helps the bird enter the water with only a very stealthy kind of impact; and it has no nostrils that would allow water to gush inward and do serious damage to the delicate tissues inside.
Modifications of the skull are many,all produced by evolution to give each animal maximum advantage in adapting to its environment.
As always when at a loss,animal behaviourists like to say that the rams carry out their butting for reasons of power,territory or sexual ritual. Their skulls give nothing away,other than being stronger than usual. The rabbit skull,however,is awash with clues as to how this particular animal behaveswhich makes it a rather more intellectually satisfying skull to collect,if perhaps not as spectacular to have on display in Dudleys upstairs bedroom.