Zig-zag track on rocks in the tidal zone. NOT thought to be either periwinkle or limpet.
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I would say limpet grazing, I'm interested to know why you think it isn't made by limpets?
The feeding track of the limpet is a zig-zag track as shown and as I said the last time this question was offered. The limpet also leaves a broader movement track and a resting position which fits a bed in the rock and to which the animal returns when resting (say between tides.) It is possible at times to trace the zig-zag to the feeding limpet.
That is what I was told anyway.!!!
We are not told of the tide level at which the observation was made but on a Northumberland shore there isn't much else apart from Patella that could make a trail of this size and pattern.
Lat/Lng: 55.576258331129, -1.6439151763916
OS grid ref: NU225314