In Pacific Grove, California, western gulls Larus occidentalis prey on chitons Nuttallina californica. This is shown by presence of identifiable shell plates in 28% of the gulls’ regurgitation pellets.  A rough estimate by the author based on number of gulls present in the area at the time of the study, frequency of regurgitation of pellets, and number of N. californica regurgitated in a pellet suggests that up to 1000 individual chitons could be consumed by this small population of 18 gulls during their 90-day breeding period.  This would represent a yearly demise of 15% of the total N. californica population that is estimated to be in the area.  In comparison, western gulls seem not to prey on another similar-sized species Cyanoplax hartwegii in this area.  Whether the differential predation on Nuttallina californica over Cyanoplax hartwegii reflects the camouflaging value of algae in the latter’s habitat, the generally more exposed position of Nuttallina on the tops of rocks, or perhaps distastefulness of Cyanoplax, is not known.  Moore 1975 Veliger 18(Suppl): 51; see also DeBevoise 1975 Veliger 18(Suppl): 47. Photograph of Nuttallina californica courtesy Ron Wolf, California and calphotos.

NOTE  out of a total of 102 pellets examined.  Shell remains of 2 other chitons Katharina tunicata and Mopalia muscosa are also identified in 8 of the pellets and in 1 pellet, respectively)