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The theoretical basis of my research project examines how rocky shore exposure to wave action at Jetty beach and Castle beach, Pembrokeshire, affects the length to aperture ratio of dog whelks at 4 metres above chart datum. The factors affecting the desiccation of dog whelks are temperature, relative humidity, wind speed and light intensity. These abiotic factors may cause the dog whelks to migrate up or down the shore depending on the varying conditions. Predation and feeding are definitely biotic factors affecting dog whelks. Crabs and birds are common predators and thicker and longer shells provide protection against crabs on sheltered shores. The reason dog whelks stay on the lower shore relative to the upper shore may be for protection against birds so they may not be seen.
Apart from the environmental factors affecting the dog whelks’ shells, genetic factors may also affect the shape of their shells. Human activity may also disrupt the species habitat. Crothers explains that dog whelks spend hours on top of their feed in order to digest it, therefore I returned them to their original spot to minimize disruption to their feeding cycle when I was measuring their shells.
Keywords: Dog-whelks, shell size, exposure
