more efficiently. Feeding habits Its adaptations include a modified radula (a toothed chitinous structure) to bore holes in the shells of prey, complemented by an organ on the foot which secretes a shell-softening chemical. When a hole has been formed paralysing chemicals and digestive enzymes are secreted inside the shell to break the soft body down into a 'soup' which can be sucked out with the proboscis. The plates of barnacles can be pushed apart with the proboscis, and the entire individual is eaten in about a day, although larger animals such as mussels may take up to a week to digest. Feeding only occurs when conditions are conducive to such an activity, and during these times the dog whelk consumes large quantities of food so that the gut is always kept as full as possible. This allows shelter until more food is required, when foraging resumes. If waves are large or there is an excessive risk of water loss the dog whelk will remain inactive in sheltered locations for long periods. Mussels have developed a defensive strategy of tethering and immobilising with byssus threads any dog whelks invading their beds, leading to the whelks' starvation. Life cycle Predators Predators of the dog whelk include various species of crabs and birds. Protection against predation from crabs which attempt to pull the soft body out through the shell aperture can be afforded by growing teeth around the edge of the aperture. Many predators cannot smash the strong shell of an adult dog whelk, but juveniles are vulnerable to attack from many predatory species. Eider ducks and various other birds simply swallow the entire body with its shell, while oystercatchers and various crustaceans are often capable of crushing or breaking the shells. In the winter they endure more predation from purple sandpipers and similar wading birds, but in the summer crabs represent a greater threat. In general, the dog whelk can be thought of as being vulnerable to birds when emersed, and to crabs when immersed. Human use The dog-whelk can be used to produce red-purple and violet dyes, like its Mediterranean relations the spiny dye-murex Bolinus brandaris, the banded dye-murex Hexaplex trunculus and the rock-shell Stramonita haemastoma which provided the red-purple and violet colours that the Ancient World valued so highly. Bede mentions that in Britain "whelks are abundant, and a beautiful scarlet dye is extracted from them which remains unfaded