Mad About Moles

A welcome post from Julian Wormald:

It’s the time of the year when one really notices moles. 

Particularly obvious if you have meadows, or pasture, and always more noticeable in early spring. I knew that this was mating time for moles, but what else did I know about these hidden mammals? What do I and others make of their (literally) handiwork? Does it drive us mad? Do we curse? Do we yearn for the tiny amber glass strychnine pot, which I remember my G.P. father using, carefully with gloved hands, dipping a few worms into the crystals, before dropping them into the vertical shaft holes having cleared the molehill soil away, before covering the shafts over again, and leaving the poor worms to find their toxic bait. Fortunately, strychnine use was banned in 2006, but that still leaves a huge range of methods employed to exterminate these hidden animals – traps of many designs, toxic gas pellets, other poisoned baits. But aside from the unsightly appearance of piles of soil, what are the downsides to moles?

Reasons mentioned mainly seem to focus on damage to the aesthetics of lawns; or to cutting machinery blades when hay or silage making from the stony molehill soil; or from the risk of contamination of silage with soil present bacteria, like Listeria, which can cause disease in animals eating the silage; as well as the potential loss of grazing, in pastures covered with many molehills.

But against these negatives, apart from the usually sensible in the longer term, live-and-let live approach to nature and ecosystems, are there any positives to having a local mole population in a garden, or pasture? It’s actually quite difficult to find meaningful information on this. We seem so determined to exterminate them, and there are real gaps in our understanding of their ecology and lifecycles. With this in mind I bought one of the few books on the life of the mole – “Moles” by Rob Atkinson, in the British Natural History Collection of books.

Well worth a read, and here are a few snippets to share about these fascinating creatures, which you may or may not already know:

  • Moles live almost entirely solitary lives, in their own independent system of tunnels, which is typically around 1.1 km in length, and will have required about 2,000 kg of soil to have been removed to create this, the mole’s territory.
  • The area that this territory covers will depend on how many invertebrates there are in the soil it’s working through.
  • Moles sleep in specially constructed nests, lined with dry material and located away from the edges of the territory.
  • Mole tunnels lie anything from 5 to 150 cms below ground surface level.
  • The tunnels are dug by alternating between the two huge hands, whilst the mole braces with its rear legs against the tunnel wall, using a shearing action on the soil at the tunnel face. The loosened soil is pushed behind the mole, using the rear feet and legs, and every so often the mole swivels around in the narrow tunnel, and pushes the loose soil spoil back down the tunnel in front of it, to an access shaft which it’s dug previously to the surface at an angle of about 45 degrees. The mole then pushes the soil up the shaft with one hand, and onto the surface as a mole hill. As much as 6kg of soil can be shifted in this way within 20 minutes. This is the equivalent of a man of average size, pushing an elephant out of an uphill tunnel, onehanded, within 20 minutes. This is hard physical effort for the mole, and bouts of digging usually last for less than 10 minutes. To dig a metre of tunnel, requires as much energy, relative to bodyweight as a 10 stone woman running at 7.5 m.p.h. for 2 hours.  
  • All this effort is fuelled by its diet based on earthworms and other invertebrates, and insect larvae which it encounters whilst digging, or more typically, which fall into one of the mole’s tunnels.
  • Sometimes moles will create larders where they store partially bitten earthworms, which may even be paralysed by some sort of venom, and these stores will help sustain a mole in times of food shortages, as can occur in periods of extreme drought.
  • Most of the year, all moles live entirely independently and only rarely come within even one metre of another mole in their separate tunnel networks, but at mating time, from February to March, male moles will actively seek out females. 
  • Meanwhile the female mole’s body has been changing. They are unique amongst mammals in having an ovotestes, and not simple ovaries. For most of the year, the ovary is small and the testis large, producing testosterone which means that the female mole is perfectly capable of fighting a male which strays into her territory. Before coming on heat, the testis shrinks in size, the ovary enlarges, and the uterus begins to enlarge from its previously shrivelled state. Even more remarkably, as she nears mating time, she develops a new opening in her skin, which communicates with her vagina. For most of the year, no such access to the vagina and uterus exists. After mating, this opening in the skin heals up and leaves a small scar.
  • Pregnancy lasts about 4 weeks and the mole pups are born with reddish skin and no hair.
  • The typically 4 pups grow phenomenally fast, fed by the lactating mother, and stay in the nest for the first several weeks. Their tiny eyes open around day 22 after birth, by which time they’re covered in silvery fur. 
  • The mother must leave them at regular intervals, hunting for food in her tunnels, before returning to let them suckle.
  • After a month or so, the young moles will begin to venture into the tunnel system and over the next few weeks start to eat solid food.
  • By week seven, the pups stop feeding on milk, but stay within the mother’s tunnel system, finding their own food, and beginning to venture onto the surface occasionally at night, eventually sleeping in separate nests, before finally being evicted and leaving the maternal territory of tunnels in early June.
  • Each pup is now on its own, and travelling above ground at night, it must find either a new unexplored territory and begin to dig, or with less effort, an abandoned tunnel network, in which to set up its own territory and try to carve out its own independent living space. This transition is a risky time for young moles, and many will be predated, by for example, foxes, stoats, and owls. 

Thinking a little more about the increase in their numbers here, does this reflect growing numbers of earthworms and soil invertebrates, as we gradually move our meadows back to more diverse plant communities?

Or is it linked to us not using any pesticide/vermicide treatments on our sheep for a few years, which has led to a greater number of worms and invertebrates? Or because none of the fields have received any slurry, muck or NPK in recent years? We’ve noticed in the light of these thoughts, how few molehills are ever obvious in slurry treated or intensively managed grassland. but is this because the farmers are killing all their moles anyway?

Finally, we’ve observed how we’re finding more molehills not just on our sloping fields, but also the valley bottom ones, where they’re pushing into peaty areas, which are still remarkably free of the all-pervasive Soft rush, Juncus effusus, which is steadily taking over our neighbour’s field across the stream.

Are moles providing an invaluable system of free, and self-maintained, below the ground, drainage channels with no need for heavy diesel powered equipment, to create them?

See what a British manufacturer of “The Magic Mole” writes;

Why Mole Draining is Important:
The TWB Magic Mole Drainer can play a crucial role in helping to achieve the potential of your soil. On the right soil type and when installed correctly, mole draining can help reduce waterlogging problems substantially. Heavy soils with low rates of water movement need regular drainage to improve soil structure and productivity. The aim of mole draining is to fracture and crack the soil and construct unlined mole channels at consistent depth and even spacing which allow flow paths for water to drain unhindered into gravel filled collector drains or dykes. The TWB Magic Mole skid design allows the leg to fracture and crack the soil without leaving excess surface disturbance, forming a mole channel to a smooth gradient evening out small surface contours and irregularities.

To recap “modern” thinking –

The moles increase in numbers. The fields drain better.

But we HATE the moles. We want them gone. We kill the moles. We celebrate our wisdom.

The rain worsens, the fields flood more, the drainage deteriorates.

So, we use a heavy tractor. The ground is compacted even more. With a mechanical “Magic Mole” we tunnel artificial mole drains.

To solve the problem.

Never mind whack-a-mole, whacky-or-what?

Here, we’ll try to play the long game for a while and see what happens. Use a bit of mole hill soil for compost and deep beds. Rake out a few of the nuisance ones in the hay meadows well before hay cutting time. Value the exercise, and the extra soil aeration the tunnels will create, and seed exposure to light. And germination. Watch the meadows change, and insects return, and try to leave the moles alone.

Julian Wormald

6 thoughts on “Mad About Moles

  1. What a fascinating article! I believe that moles also play a role in the biodiversity of meadows, especially those which are not grazed. As we know, many wildflowers need bare soil in which to germinate; where does this bare soil come from without grazing, if not from molehills? I have noticed that our molehills are currently covered with seedlings.

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  2. Totally agree with the last paragraph. I’m slowly raking out almost six acres of hay meadow covered with mole hills, so that there will be fewer obstructions to scythes later in the year. I’m not exactly dancing with joy about doing it but I’m not going to kill the moles. I’m sure you’re right that the moles are both indicators of healthy invertebrate and worm populations and providing us with services we don’t fully appreciate. And mole hills are great in the garden. Great mole background info – thanks!

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  3. Another thought provoking article Julian. I hadn’t thought of the water draining effects of moles.
    As we manage our grasslands at the National Botanic Garden of Wales for biodiversity, we leave the moles alone. I suspect moles help wildflower seed to spread across newly restored meadows, as do badgers when they scrape the ground looking for grubs and worms. I also tried out an experiment last autumn of hand pressing wildflower seed I’d collected into the loose soil of mole hills to encourage their spread.
    In the 1990s, an old boy naturalist suggested to me that greater number of mole hills we were seeing in winter indicated global warming – the soil is less frozen and so more movable. Might be rubbish but it’s a thought.

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  4. Just brilliant – thanks so much for bringing this to our attention. We look after a heritage apple and pear tree orchard in an former intensively grazed and managed field and the moles have steadily been increasing our side of the fence but not in the adjacent fields. We just rake or kick the mole hills over in the spring before scything in early June – otherwise they’re left alone and we love them!

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  5. Thank you …. I’m deffo gettin’ me monies worth with this club An SA32er

    On Wed, 7 Apr 2021 at 10:29, Carmarthenshire Meadows Group – Grŵp Dolydd Sir Gaerfyrdd

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  6. Thank you for the insight. I removed my 2 traps this afternoon after reading this feeling very guilty. All very very interesting. Thank you!

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