The River Greet, a tributary of the R, Trent, rises in Belle Eau Park near Bilsthorpe, Notts. About two miles from its source it has been deepened and yridened to form the lake within the grounds of Kirklington Hall. The water from the lake passes over a weir into the stream which flows under the main drive, and then under the main A6l7 Mansfield to Newark road. Anodonta anatina (L.) lives at the lower end of the lake in association with Sphaerium corneum (L.), Potamopyrgus ,jenkinsi (Smith), Planorbis leucostoma, Millet and Lymnaea peregra (Muller).
After heavy or prolonged rain the sluice gate by the weir is opened, and the rush of water carries both mud and mussels into the stream, the latter as far as the main road bridge. These Anodonta anatina show a great deal of variation in size and shape.
During the first two weeks of May 1957 I spent a considerable amount of time in the grounds of Kirklington Hall. I was able to make observations and record incidents of herons, moorhens and rats preying on A. anatina. Usually about mid-morning a pair of herons would fly over the lower end of the lake and alight in the stream. They would soon secure a mussel, carry it in their beaks into the adjacent field where the mussel would be firmly clamped to the ground by the foot before being pecked open. Sometimes the herons would take flight and drop the mussels from a height of 20 feet, whether by accident or design I cannot say - but the bird would always make a rather ungainly descent and proceed to feed on the mussel. The moorhens were content to attack and feed on the smaller specimens of mussels living on beds of shingle in very shallow water. These birds attack the mussels very aggressively about the ventral margin, to make an opening large enough to be able to peck at the soft parts of the mollusc.
On the right bank of the stream, I noticed several rat runs, which went towards two yew bushes at the rear of out-buildings of the adjacent farm. Around the rat holes were living and dead mussel shells. From the evidence of dead shells which lay about, the pattern of attack was much the same as that of the moorhens, part of the ventral margin and the posterior portion of the shells had been gnawed away. A few of the mussel3 had only a small portion of the posterior end gnawed away, but the hole thus made was large enough to see the mollusc within. May be something had disturbed the rat when it was earnestly preparing to make its meal. I have seen the water- vole taking young Anodonta for food, in the River Meden, Thoresby Park (see TJ.C.', Vol. 23, Ho. 10, p.338).
C. W. Pitchford