Profitable Wonders
James Le Fanu
There are, it is estimated, an amazing thirty million moles in Britain. Who would have thought it? Their earthworks might be familiar enough but few people are privileged, like Captain Sidney Rogerson of the West Yorkshire Regiment, to meet a mole face-to-face. In November 1916, as the Battle of the Somme was drawing to a close, Capt Rogerson was briefly diverted by a scuffling in the wall of his trench out of which tumbled a plump velvety mole. ‘It appeared as one of Nature’s miracles that this small blind creature could have survived in ground so pounded and upturned,’ he remarks in his memoir of life at the front, Twelve Days on the
Somme. Having ‘marvelled at the strength of those tiny limbs’, he relocated his accidental visitor ‘to find its way back whence he had come’. ‘A few clawings at the earth and he had disappeared … how I wished we could dig ourselves in so easily!’
The back-breaking labour of trench excavation would certainly be vastly less onerous were we to possess the mole’s astonishing tunnelling skills whereby each of the string of molehills that erupt seemingly overnight on lawn or field is the equivalent, in human terms, of excavating a mound of earth twelve feet high and twenty feet in diameter – without the aid of shovel or wheelbarrow.
The secret life of this furious bundle of energy concealed from human gaze in its network of subterranean passages hundreds of metres long ranks among the strangest in the natural world. The practicalities of its soil-shifting prowess reside in a unique series of adaptations, most obviously its characteristic spadelike hands. The short stubby fingers and sharp claws bound together by a tough web of skin are widened still further by an extra sickle-shaped sixth digit, an enormously expanded modification of the minuscule sesamoid bone at the base of the thumb. The palms facing outwards and backwards so as to sweep against the tunnel wall are powered by half a dozen athletic muscles tethered to the bones of the upper limb, again specifically modified to facilitate digging – massive shoulder blades projecting far above the spine and the shortened but solidly built humerus.
Thus equipped, the mole can shift 150 times its own weight of earth in less than an hour. Braced by its hind limbs, the mole digs first with one hand and then the other before turning around to shovel the recently excavated soil back along the tunnel and then up into a previously constructed ventilation shaft to form a mole hill. The energy expended in the Herculean task of tunnelling up to twenty metres a day is estimated to be 4,000 times greater than traversing a similar distance above ground.
Back in the 1980s, zoologist Dr Martyn Gorman of Aberdeen University trapped, with considerable difficulty, fifteen moles on the Haddo Estate and by attaching a tiny radio transmitter to their tails was able to track their movements. Moles are solitary creatures, and sure enough, though living in close proximity, each patrolled its own exclusive network of tunnels, foraging for any worms, their staple food, that may inadvertently have burrowed their way in. The only diversion from this uneventful wellprovisioned life comes in early spring at the onset of the mating season. In a frenzy of activity, the males dig a further set of straight tunnels radiating outwards in the hope of breaking into the home range of a receptive female. ‘Such social contact is brief indeed’, Dr Gorman writes, and, coition completed, the males retire back to the solitude of their previous existence. Their offspring, once weaned, spend a few months exploring their mother’s domain before being unceremoniously evicted to fend for themselves as best they can.
It is very difficult, impossible, to imagine what it must be like to be a mole, almost blind, living alone in a state of perpetual darkness, cut off from the sights and sounds of our familiar world. But Capt Rogerson’s brief encounter would never have happened were the mole not a great survivor acutely attuned to the demands of its unusual existence. The mole’s salvation lies in its pink snout, reputedly the most sensitive mechanosensory organ of perception in the animal kingdom. It comes covered with tens of thousands of tiny raised papillae, ‘teletactile receptors’ that can detect minuscule changes in air pressure, temperature and infra-red radiation. Meanwhile, the movement of the sensory bristles (or vibrissae) under the chin, on the side of the face, and on tail provide the essential information by which the mole navigates its way through its domain. ‘It is very likely that the mole’s world of touch is as rich in detail as a dog’s world of smell,’ writes Dr Gorman, ‘and just as incomprehensible to a visually oriented species such as ourselves.’