A hunter’s leftovers had been discarded around the shores of a farm reservoir close to the river. It looked like the aftermath of a messy banquet. Furnished with clues, I began playing nature detective.
The first piece of evidence beckoned out of the long grass, the pearly saucer of a freshwater mussel shell, spacesuit silver with glints of yellow, blue and paraffin pink. Its other half, close by, lay sunny side down, the dull grey-brown outer coat speaking of the muddy bottom of the lake from where it was grabbed. Living in those dark depths of the shallows, camouflaged by its drabness, it would have kept its shiny here-I-am interior shut.
But an animal had found, fished and prised this mussel open, unhinging its two inseparable parts. And, as I quickly discovered, the predator had repeated the trick many times. I followed a litter trail of broken shells down to the water’s edge.
Just below the surface, some complete shell halves had bedded down on a weedy blanket of hornwort and milfoil. Others were strewn along the beach. There was a morass of faint, smudged and half-obliterated footprint impressions in the bare clay, and stinky big clues as to their owner. The irregular piles of uniformly coloured and frankfurter-sized fibrous poo pointed to a regular dog walk and a habitual toilet. But no dog would be capable of trawling a lake bottom for molluscs.
I scouted around the lake, the surrounding banks and meadow, and felt the story coming together. All the shells lay at the north and north-west sides of the reservoir. The farther away from water, the more broken the shells. It suggested an animal on a regular beat that would carry away those mussels that it could not lever apart and eat immediately, to the grass above, where it could sit down and pulverise them.
One of those smashed shells was still hinged but looked like a book that had been bitten in half and then spread open to show mirror-image bite marks on facing pages. Big bite marks too, the kind that might have been made by an otter or a mink. Whatever animal left its mark, it had a voracious appetite for shellfish.
