British Wildlife of the Week

Mole

With an estimated population of over 40 million, the European mole is one of the most common mammals in the British Isles. Yet it is one that we hardly, if ever, see. The only clues that might give away its presence are the odd clumps of soil that we call molehills. Of course, it’s hardly surprising that the mole is so elusive because it spends virtually the whole of its short but active life underground, safely hidden from predators above.

There are few animals more supremely adapted to a subterranean existence than the mole is. Although it’s not completely blind as people often assume, its tiny, rudimentary eyes, practically useless underground, have become covered in fur and can do little more than recognise light and dark, and detect some movement. The mole’s main sensor is, instead, its nose. Covered with many sensory bristles, it is an organ of both smell and touch.

Meanwhile, the animal’s short, soft, velvety fur, which is almost uniform in length over its whole body, has no particular grain so that it points in all directions. This means a mole can move forward and backwards through its tight passageways with equal ease. As it does so, its tail points up like a flagpole to feel the way, which is especially useful when the creature needs to shift into reverse.

The tunnel system that an individual mole lives in can cover an area the size of four football pitches, and its inhabitant will traverse these passages daily in its search for food. Thanks to its strong shoulders, stocky forelimbs and flat, spade-like hands, which are almost as broad as they are long, the mole is a superb digger and it is frequently expanding its tunnels. It works in four-hour shifts, alternating between frantic digging/eating and sleeping deeply. It has been calculated that in just 20 minutes, a single mole can shift 6 kg of soil – the equivalent of a human moving four tons in that time.

Excavated soil is pushed up vertical shafts and out onto the surface in heaps, creating the familiar molehills that infuriate proud lawn-owners, farmers, and the keepers of golf courses so much. Each molehill weighs 1-2 kg – more than 10 times the weight of the animal that built it. It’s little wonder that the word ‘mole’ comes from the Old English mouldwarp, which means ‘earth-thrower’.

This extensive network of underground passageways is not only a home for a mole; it also acts as a food trap, with worms and other soil-dwelling invertebrates simply falling in through the walls and ceiling. The resident mole scurries up and down every stretch of its tunnel system, capturing these creatures before they can escape. If the mole wishes to eat a worm then and there, it first removes all the dirt and earth from the worm’s skin and then pulls the worm tightly through its forepaws so that the dirt in the worm’s gut is also squeezed out, rather like we squeeze toothpaste from a tube.

Vast numbers of worms can be consumed every day. On the occasions when so many worms collect in the tunnels that even a mole’s considerable appetite is sated, this little mammal gathers up the surplus, immobilises them with a quick bite to the head, and then stores them away, still alive, in an underground larder for later consumption. Larders with over 1,000 paralysed worms are not unheard of. 

The mole is a solitary and belligerent animal that is extremely territorial over its tunnels. Should another mole intrude on its territory, the original inhabitant will viciously attempt to expel it. Female moles even develop testicular tissue, which produces the testosterone they need to aggressively defend their home. Only in the spring, for a couple of weeks a year, do the testosterone levels of both sexes go down. It is then – and only then – that they tolerate the presence of others of their kind, coming together peacefully, albeit briefly, to reproduce.

Despite being so plentiful, moles remain little studied and their behaviour is among the most mysterious of any British mammal. They are very difficult to see and almost impossible to observe for any length of time. Sadly, your best chance of seeing a mole is if you own a cat, since your pet may bring back live victims to play with. But soggy winters can also sometimes yield more frequent sightings because wet, heavy soils bring worms to the surface, prompting moles to dig much shallower runs. Rain also causes tunnel collapses, forcing moles to temporarily flee their underground homes.

Unfortunately, although I’ve seen many molehills in my life, I’m not yet among the privileged few that have come across a live mole. Of all British mammals, it is perhaps the one I would most like to see. I’ve always had a particular fascination with these secretive but determined diggers – and because of that, The Nature Nook is designating January as ‘Mole Month’. For the next three weeks, we’ll be bringing you articles on just a few of the weird and wonderful members of the mole family from around the world!

The European mole may be one of our most common mammals, but in the next British Wildlife of the Week, we’ll be looking at one of the rarest. Perhaps surprisingly, it is the black rat.