An Analysis of Gray and Harbor Seal Strandings in Cape Cod, Massachusetts from 1999 to 2012.
Abstract
In recent years, the number of gray seals, Halichoerus grypus, inhabiting Massachusetts
has increased dramatically. In Canada and Scotland, similar increases in gray seal
abundance have been accompanied by a concomitant decrease in numbers of sympatric
harbor seals, Phoca vitulina. It has been hypothesized, although not confirmed, that
interspecific competition between the two species led to a decrease in harbor seal
populations. The present study addressed the question of whether gray seals and harbor
seal populations are interacting in Cape Cod, MA by analyzing stranding data from
Cape Cod in the period from 1999 to 2012, provided by the International Fund for Animal
Welfare (IFAW). Gray seal strandings increased 2.9% annually from 1999 to 2012. Harbor
seal strandings, on the other hand, increased 8.5% annually until 2004, after which
the increased stopped and the number of strandings varied interannually. Strandings
were best predicted by species, age class, and month, although age class only affected
harbor seal seasonal stranding trends. Seasonal trends in the number of gray and harbor
seal strandings caused by human interactions were significantly different. These differences
in the stranding record suggest that the two species are interacting ecologically
in Cape Cod.
Type
Master's projectPermalink
https://hdl.handle.net/10161/8533Citation
Frungillo, Jaime (2014). An Analysis of Gray and Harbor Seal Strandings in Cape Cod, Massachusetts from 1999
to 2012. Master's project, Duke University. Retrieved from https://hdl.handle.net/10161/8533.Collections
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