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Species - Whelk, dog
Whelk, dog (Nucella lapillus)
Shell is usually about 3 cm high and 2 cm wide, but may grow to 6 cm. Rounded with a pointed spire, a short, straight siphonal canal (a groove on the underside of the shell) and a deep anal canal. Overall shape varies according to degree of exposure to wave action on the shore where a population lives, but the body whorl (largest section of the shell where the majority of the visceral mass is located) is usually around 75% of total length. The aperture is usually crenulated in mature dog whelks, less often in juveniles. Shell surface can be fairly smooth interrupted only by growth lines or, when the snail is living in more sheltered areas, can be somewhat rough and lamellose. The surface is spirally corded. The outer lip is dentate and ridged within. The columella is smooth. External shell colour is usually whitish grey but can be orange, yellow, brown, black or banded with any combination of these colours. They are occasionally green, blue or pink.
Dog whelks gather for mating in spring. Eggs are laid in yellow capsules in rocky crevices during April and May; about 5 capsules per female, each with about 600 eggs. The young feed on unfertilised eggs, which are in the majority, before emerging as small replicas of the adults. Juveniles are susceptible to drying out if exposed above the waterline at low tide, and a large proportion die in this way. Maturity is attained after three years.
Diet consists of mussels and acorn barnacles. They have special drilling mouthparts to bore through the shells of other molluscs. Predators include several species of crabs and birds. Eiders and some other birds simply swallow body whole with shell, while oystercatchers and crustaceans often crush or break the shells first.
The dog-whelk can be (has been) used to produce red-purple and violet dyes,