title for learn-about sections for chitons in A SNAIL'S ODYSSEY
  Predators & defenses
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Vertebrate predators


Vertebrate predators such as birds and sea otters are considered in this section, and INVERTEBRATE predators in another section.

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Research study 1

photograph of western gull Larus occidentalisIn 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 individualchitons 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.photograph of chiton Nuttallina californica

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)

Nuttallina californica 1.5X

  Sea otters & humans
Research study 1

photograph of black leather chiton Katharina tunicata courtesy Linda Schroeder, Pacific Northwest Shell Club, SeattleBlack leather chitons Katharina tunicata on the Kenai Peninsula in south-central Alaska have historically been harvested by indigenous peoples.  This tradition has continued to the present day, but recent declines in population numbers of Katharina have prompted researchers from the University of Washington and the Sugpiaq Native Village, Kenai Peninsula, Alaska to investigate possible causes.  Comparison of current fishing activities and natural predation at 11 rocky intertidal sites on the Peninsula suggest strongly that the decline owes to a combination of human exploitation and sea-otter Enhydra lutris depredation.  The authors find good correlation between annual per capita harvest effort by the local peoples and Katharina density, and between sea-otter presence and chitons.  Basically, at the sites where fishing pressure from humans is high, sea-otter and chiton densities are low, and where sea otters are common but human fishing-pressure low, chitons are also sparse.  Other predators, such as birds and sea stars, and other environmental conditions, such as wave exposure and temperature, seem not to be involved in the decline.  Salomon et al. 2007 Ecological Appl 17 (6): 1752. Photograph courtesy Linda Schroeder, Pacific Northwest Shell Club, Seattle PNWSC.

NOTE  the authors cite early anthropological reports that indicate that chitons have been harvested in the area for at least 3000yr.  Sea otters began to recolonise the area from the 1960s

NOTE  first noted 10-15yr ago

Research study 2
  photograph of black-leather chitons Katharina tunicata ready to be eatenAn account by a researcher doing archaeological studies of midden sites along the coast from southeastern Alaska to northwestern Washington indicates that chitons Katharina tunicata have been consumed by indigenous peoples from at least 10,000ybp. Most meat yield from a chiton is, of course, from the foot, but gonads and other parts of the gut are not only tasty, but also likely more nutritious than the foot musculature. Indigenous elders say that soaking a live chiton in freshwater not not only straightens it through swelling, but also makes the flesh more tender. Eating uncooked foot muscle is likened to chewing gum. Meat yield from common midden food invertebrates is ranked in order: California mussels (highest), then black-leather chitons, butter clams, and littleneck clams, and this order generally reflects their ranked order of appearance in middens. Croes 2015 J Northw Anthropol 49 (1): 13; photograph courtesy the author.