Analysis Of The Size, Shape, And Modeled Age Of Common Limpets (Patella Vulgata) From Late Norse Middens At Sandwick, Unst, Shetland Islands, Uk: Evidence For Anthropogenic And Climatic Impacts

Zooarchaeological faunal remains are commonly examined to investigate harvesting behavior. We determined limpet (Patella vulgata) shell size and shape, and estimated shell age from several middens at the Late Norse Sandwick South Site, Unst, Shetland, UK, whose strata represent distinct occupational phases (Phase 1: AD 1100-1200, Phase 2: AD 1200-1250, Phase 3: AD 1250-1350). Our goal was to determine if the many limpets found there could provide insight into Norse harvesting behavior. Shell length, conicity, and modeled age all declined between Phases 1 and 2, suggesting intensive, size-selective harvesting of limpets and a shift to harvesting lower in the intertidal zone between phases. Length and conicity varied in Phases 2 and 3 and no major changes seem to have occurred over these periods, indicating that harvesting maintained the limpet population at an impacted level throughout the later phases. The conicity decline between Phases 1 and 2 may also have been caused by increased storminess that accompanied the onset of the Little Ice Age. The mean length of modern limpet populations near the Norse site did not differ from the archaeological phases, but did vary among collection years. Limpets were 26% larger in 2015 than in 2012 and 2013, indicating that large interannual variations in population structure can occur over short time periods. Potentially the result of extreme storms removing small limpets, this result raises the possibility that size and conicity changes during the Sandwick South Site occupation, as well as in other early populations, could also be the result of environmental factors rather than human harvesting alone. We feel, however, that the most parsimonious explanation for the patterns we document is human harvesting.