IMPACT OF HUMAN PROVISIONING FROM THE CHATHAM FISH PIER ON THE ECOLOGY OF GREY SEALS (Halichoerus grypus) (2016)

Undergraduates: Rachel Voorhis, S.M. Sharp, J.H. Moxley, A. Barratclough, A. Bogomolni, R. DiGiovanni, M.O. Hammill, D.W. Johnston, K.M. Moore, M.J. Moore, W.B. Sharp, G. Waring, M. Polito, L. Sette

Faculty Advisor: Rachel Noble
Department: Environmental Science

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Human provisioning (feeding) of otherwise wild animals has been shown to significantly alter their body condition and behavior as compared to other members of the population. However, the vast majority of these studies tends to focus on either physiology or behavior, and thus do not provide a holistic assessment of the impact of provisioning. The recent population boom of grey seals (Halichoerus grypus) in the western Atlantic and their proximity to humans makes them an ideal candidate for such a study. Morphological data was collected and GPS tags deployed for several seals in Chatham Harbor, Massachusetts in June 2013. Movement analysis that suggested one seal was provisioned via the Chatham Fish Pier, and the assumption was later verified by photo identification. The provisioned female (#709) was particularly small in terms of length, weight and girth for her age, and exhibited significantly decreased blubber thickness compared to other female seals in the study. Stable isotope analysis determined that #709 was foraging (or was fed) prey items from a higher tropic level than normal, as well as indicated high levels of inshore feeding. Home range, trip and behavioral analysis generated by GPS tag data suggest that the provisioned seal deviated from 'normal' patterns of movement including number, location and length of foraging trips, home range size and location, and breeding behavior. The cumulative analysis is limited by a small sample size, but implies that further research of this type could support a direct link between human provisioning and significant deviations in grey seal ecology.