There’s a Leech at the Bottom of my Garden

Horse Leech

I was digging in my garden a few weeks ago, in a pretty damp area. After some considerable huffing and puffing, the small bush I was removing came out, root and all. The clay soil was not keen to let the bush go, but I eventually came out on top. As I wiped the sweat off my brow and examined the hole left by my labours, I noticed a very stunted earthworm. Well at least that is what I thought it was. It was about 3 cm long and 1 cm thick. At first I thought I must have severed it in two. Closer examination revealed that it was curled into a horseshoe shape. At one end the worm was thickened, as though it had a sucker.
That final observation clinched it for me. This was not an earthworm, but a leech. My experience of leeches is restricted to ponds, where the biggest I had seen were perhaps no longer than 4 or 5 cm fully extended. My immediate thoughts were “medicinal leech”, as I rushed over to show it my wife. She too was digging in the garden. “I found a small one of those earlier. I thought it was a slug” she said “So I squashed it”. Non-plused by her heavy handedness and her lack of identification skills I headed indoors to discover more about it.
I was well aware that a medicinal leech is something of a rarity in the UK. Identification of a curled up stump is always going to present problems, so I thought I’d encourage the monster to reveal more of himself by putting it in a container of water. It is astonishing how a bit of water can make a leech grow! Like Pinocchio’s nose it grew longer and longer, until it finally stopped at somewhere between 13 – 15cm. I realised that this was potentially an exciting find.
I live in East Sussex, about 25 to 30 miles from Dungeness. Dungeness is one of only a dozen or so sites in the UK to host a population of Medicinal Leeches (Hirudo medicinalis). H. medicinalis is the European medicinal leech, there being a few other medicinal leech species around the world. The European medicinal leech is a protected species due to its rarity, partly because of its over-collection in the 19th Century, for the bleeding industry (blood-letting by doctors), and partly due to loss of habitat.
I wondered if a leech could find its way to my back garden from Dungeness. They are unlikely to swim or even crawl such a distance, but they are not averse to hitching a lift on an avian host. Lots of Dungeness water birds are capable of such a trek.
I have a few freshwater invertebrate books in my collection, but they are of limited value for identification purposes. So I decided to check out the Internet. I checked Wikipedia and got some reassuring information there. Other sites revealed how limited its range is. I was starting to think I had found something special. However, it was obviously now time to call in the experts. My hands were shaking, as though I’d found a Viking gold haul in my back garden. A phone call to Romney Marsh Countryside Project started badly, all I got was an answerphone message. I decided to keep my excitement in check and left a message in a matter-of-fact voice. No point in getting too excited, especially when they have a few thousand of the little beasts in their own back garden.
Who should I try next? I decided on English Nature, or is it Natural England? After 10 years I still get mixed up between the names. I got a lady on the switchboard, who was unaware of what a medicinal leech is. This was disappointing, but at least she passed me to someone who did. He suggested I contact the Natural History Museum. This I did, my excitement now turning to frustration. They too were unexcited by my leech, but at least asked me to send a photograph. I suppose they get all sorts of public ringing up with ‘rare’ sightings. Anything from “there’s a green parrot in my apple tree” to a sighting of the Beast of Bodmin.
Most of ‘Joe Public’ have little idea of what British wildlife is, let alone if it is rare or not. I used to run an environmental education centre in Canterbury and often had distraught ladies telling me “I’ve got a snake in my toilet. What should I do? Will you come and take it away?” I usually passed them on to Kent Amphibian and Reptile Group. Now it was my turn to get the same treatment.
Fortunately, at that moment Romney Marsh Countryside Project rang me back. A very helpful gentleman called Owen asked me a few questions and told me quite a bit about leeches and their local distribution. Lack of funding meant that they no longer conducted medicinal leech surveys, but he suspected that they were to be found in water courses spread between Romney Marsh and Pevensey Levels. This picked me up, as I live within that range. He then went on to ask me if it had a mouth shaped like an upside-down Mercedes sign (in which case it was a medicinal leech), or an ‘O’ shaped mouth. Of course I had no idea. I offered to send him a photograph, which he agreed to look at.
No sooner had I put the phone down, then I was on my hands and knees next to the pot of water in which my leech was still thrashing around, trying to stare down the throat of this vicious monster, in order to ascertain its facio-maxilliary morphology. You can imagine my disappointment when the little beast could only form its mouth into a simple vowel sound. Not a Mercedes in sight!
I despatched my photograph and within an hour or two Owen rang back. No it was not a medicinal leech, which normally have some distinct patterning along their bodies. Apparently it is more likely to be a horse leech. These creatures do not (of course) eat horses, despite their prodigious size. Neither do they parasitise them. “So what do they eat?” I asked. “Mostly small worms” Owen advised.
On Owens advice I decided to return the leech to my garden, into a small pond I have there. Being a resourceful chap I am sure he will find plenty of invertebrates to eat either there, or perhaps on one of his forays hunting worms in my vegetable patch.
A large area of woodland backs onto my garden. At night time strange screams can sometimes be heard coming from out of the blackness. Probably a dying rabbit or unfortunate squirrel in the wood. My thoughts however turn to my leech on these occasions and by a prodigious leap of imagination I wonder if it has grown still further, and if so how big, and if so what might it eat? People have reported seeing large shadowy shapes in the woodlands of the High Weald. Some suggest perhaps a black panther.
Of course I realise that a huge carnivorous leech is a highly unlikely candidate. Nonetheless, I confess that on these occasions I give a shiver at the thought and hastily returned indoors!

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david horne

I am a Forest School leader, interested in developing a love of the environment amongst children. Forest School and related educational activities draw children outside to enjoy the natural world. This is essential if they are to be the next generation of environmental guardians. I have a degree in Botany/Geology and have been in environmental education since 1979 working for a number of organisations, such as the Field Studies Council, Canterbury Environmental Education Centre, Essex Wildlife Trust, London Wildlife Trust, Wat Tyler Centre, Surrey Wildlife Trust, Bromley Environmental Education Centre and Wilderness Wood. I currently work freelance with schools and other organisations. I would like to write regularly for children and those interested in their education, looking at the world through the eyes of a child, rather than as an expert.

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1 Response

  1. I liked your article, but wonder about the identification. I’ve seen lots of horse leeches (Haemopis sanguisuga) but don’t recall one with two faint longitudinal stripes down the back, which yours shows clearly. It’s interesting that it was found some distance from a pond, too. I wonder if it might be Trocheta subviridis, which is another large species, semiterrestrial (breeds in ponds but wanders), is often striped, and has a body with segments alternating 3 broad and 5 narrow segments. It’s not easy to see in the photo, but I can almost convince myself that the part nearest the ruler, where the segments are clearest, that there are some wide and some narrow ones. I’ve not seen the species myself, and there are not many records of it, e.g. https://data.nbn.org.uk/Taxa/NBNSYS0000022376/Grid_Map but then, leeches are quite poorly recorded…

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