Dog whelks are carnivorous and like to feed on mussels – if you find a mussel with a hole in its shell, it has been eaten by a dog whelk. They use their razor-like tongue to drill through shells. This is pretty gruesome, mussels get their own back by spinning out their byssus threads onto the dog whelk. The dog whelk is unaware of this so once they have finished eating and they try and slither off to find more food, they realise they are stuck fast and die of hunger. Dog whelks are cooked the same way as periwinkles and have a liver-like flavour.