<P> Breeding occurs in California from March to May, with pupping between April and May, depending on local populations . As top - level feeders in the kelp forest, harbor seals enhance species diversity and productivity . They are preyed upon by killer whales (orcas) and white sharks . </P> <P> Considerable scientific inquiry has been carried out by the Marine Mammal Center and other research organizations beginning in the 1980s regarding the incidence and transmission of diseases in harbor seals in the wild, including analysis of phocine herpesvirus . In the San Francisco Bay, some harbor seals are fully or partially reddish in color, possibly caused by an accumulation of trace elements such as iron or selenium in the ocean, or a change in the hair follicles . </P> <P> Although some of the largest pupping areas harbor seals are found in California, they are found north along the Pacific Coast of the US in both Oregon and Washington . Large populations move with the season south along the West Coast of Canada and may winter on the islands in Washington and Oregon . </P> <P> Harbor seals are normally found along the Atlantic Coast and islands from Maine southward to Massachusetts . Occasionally, areas further south in Connecticut, Long Island, New Jersey, and even North Carolina have reported small populations or stranded seals have been found in and near islands or on beaches . Harbor seals move south from eastern Canadian waters to breed along the coast of Maine in May and June, and return northward in fall . Massachusetts is the southernmost point of known pupping areas along the Atlantic Coast . </P>

What is the average weight of a seal