Sets of Nucella canaliculata egg capsules were collected from Bodega Marine Reserve (n = 18) and Soberanes Point (n = 4) in 2020. The dogwhelks from Soberanes Point were used as a control because previous research showed that this population consists of individuals with strong drilling phenotypes and little variation among individuals (Sanford & Worth 2009). Egg capsules from the same cluster were held together in laboratory tanks in mesh-sided containers and considered 'families' of dogwhelks. Dogwhelks were hatched at Bodega Marine Laboratory and dogwhelks from each family were split into four mesh-sided containers. For the first 3 weeks, all dogwhelks were fed a diet of thin-shelled Mytilus trossulus collected from Bob Creek, Oregon. Early life mortality of dogwhelks during this life stage can be very high (Spight 1975) so this time interval was necessary to prevent mortality from being too high, as this diet is known to result in high survival (Sanford & Worth 2009). After 3 weeks, all dogwhelks were switched to one of the four early-life diet treatments: a control diet of thin-shelled M. trossulus, M. californianus from Soberanes Point, M. californianus from Bodega Marine Reserve, or acorn barnacles (Chthamalus dalli). The two M. californianus treatments were meant to represent differences in shell thickness because preliminary research had shown that adult M. californianus from Bodega Marine Reserve have thicker shells than those from Soberanes Point. Containers were checked weekly to replace food and remove any dead dogwhelks. After 3 months on the experimental diets, total mortality was determined.