Animal

Country diary: finding a shapeshifter in the stream


The children dabbled in the stream, welly boots filling with water as they pushed their transparent pots into the cool flow. Soon we had a collection of freshwater shrimps of varying sizes; spindly crustaceans that danced in the water like seahorses.

But what was that? A shapeshifter morphing: dark gelatinous blob one moment; long, reaching worm the next. A leech – the size of a pound coin or, stretched out, about 10cm long. The immediate reaction was disgust mingled with fascination – it must be the knowledge that it can feed on our blood. We eyed it warily, as if it might somehow leap out of the pot and do just that.

Leeches are mostly aquatic and usually live in freshwater, although there are some saltwater species. Their vampiric reputation is only partly accurate – many UK leeches survive on small worms, tadpoles or larvae, eating them whole. Others latch on to ducks or fish. Only the medicinal leech, the largest British species, feeds on humans. Used for bloodletting in the middle ages, they were over-collected and are now designated a “near-threatened” protected species in the UK. They are still farmed for medicinal purposes – the anticoagulant they produce can be used to prevent blood clots following surgery.

I overcame my initial caution and placed our leech on the back of my hand for a closer look and with a perverse curiosity to see what it would do. It raised one suckered end, waving and probing the air blindly. The other sucker firmly gripped my skin. I held my breath, anticipating the engagement of several hundred tiny teeth, wondering if I would scream. But nothing happened. It flattened down, blob-like again, releasing any hold. Maybe it wasn’t peckish – a full feed on a mammal can sustain a leech for months – or, most likely, it wasn’t the type to feed on humans. It was probably a horse leech (Haemopis sanguisuga), whose name refers to their relatively large size rather than preferred dinner; they eat midge larvae and snails, although they will venture on to land to predate on earthworms.

I told my grandfather about our leech. He used to keep the medicinal variety as pets in the 1930s, letting them feed on his arm until they fell off, sated.



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