Habitat selection and distribution of harbor seal females with pups in Glacier Bay National Park, Alaska

Mathews, E

Understanding the distribution during, and timing of, reproductive activities is a crucial aspect of managing wildlife populations. Harbor seals (Phoca vitulina richardsi) are the most common marine mammal in the Pacific Northwest (Hoover, 1994) as well as in Glacier Bay National Park in Southeast Alaska. More than 7,000 seals currently use waters and haulouts in the Bay, and Park waters appear to be particularly important during pupping and mating periods (Calambokidis, Steiger et al. 1984; Mathews 1995). Johns Hopkins Inlet, a glacial fjord in Glacier Bay, has the largest known breeding aggregation (~4,000-5,000) of seals remaining in the State (Hoover-Miller 1994; Mathews 1995). A primary goal of the work described in this report was to identify and rank the importance of haulouts where harbor seal females rest and nurse with their pups in Glacier Bay. I also set out to begin characterizing the habitat type of haulouts used during pupping and breeding. Information from this study may be used to determine if the Park Service's seasonal closures to boats and foot traffic are appropriately located to minimize the likelihood of disturbance at prime pupping and rearing sites. The specific objectives of the work described in this report were to: 1)develop methods to determine which haulouts were used by mothers and pups during June, 2)categorize these haulouts by the number of mother-pup pairs observed, 3)categorize them according to the proportion of pups present, and 4)determine if females with pups were more likely to haul out on rocky substrates or if they were more common on sandy beaches or reefs. An additional objective was to begin building a GIS (Global Information System) database with information on the locations of June and August haulouts, numbers of non-pups and pups found at each haulout during June surveys, and the substrate type (glacial ice, rocky intertidal, and sandy intertidal) of each haulout. I was also interested in assessing whether females with pups tended to prefer haulouts of one type of substrate over another.