Thesis (M.A.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 123-127). Also available via the Internet.

Thesis (Ph. D.)--University of California, Davis, 2004. / Degree granted in Molecular, Cellular, and Integrative Physiology. Includes bibliographical references. Also available via the World Wide Web. (Restricted to UC campuses)

A conceptual model is proposed that describes the dynamics of the Pribilof Islands North Pacific fur seal (Callorhinus ursinus). It is suggested that fur seals are regulated most strongly at population levels close to the limits set by the availabilities of food and breeding space. Population growth appears to be primarily regulated by changes in the rates of survival, reproduction, and dispersal of young animals. The proposed conceptual model is used to shape a mathematical formulation that incorporates basic fur seal life history features. The simulation analysis is able to explain the decline of the Pribilof Islands population by reconstructing pup estimates and counts of adult males over the period 1950 to 1980. Simulation results show that commercial female harvesting and a series of poor juvenile survival rates were responsible for the observed decline in pup production on Saint Paul Island. The lower number of bulls counted during the last two decades can be accounted for if adult male survival was higher during the 1950s. The decline in adult male survival, possibly due to debris entanglement, does not appear to be equally true of females. The major driving variable of the fur seal system and the key factor that accounts for the overall decline of the Pribilof herd is the survival of juveniles. In this regard, the continued population decline through the 1980s appears to be maintained by exogenous factors that are independent of current management practices. Model results are considered reliable if simulation parameters (particularly adult survival) contain little error. A detailed procedure for analysing the sensitivity of model output to errors in simulation parameters is described in an adjoining appendix as is a revised procedure for estimating the survival of juvenile fur seals. The thesis concludes with recommendations for future research. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 97-117).

Thesis (M.S.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (February 16, 2010) Includes bibliographical references (p. 82-86)

Thesis (M.F.A.)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: Ronald Tobias. Includes DVD. Includes bibliographical references (leaves 29-31).

This thesis builds a demographic profile of the Northern Fur Seal (NFS) population being consumed at DfSi-4 and DfSj-23 to determine if a NFS rookery existed within close proximity to both sites. A demographic profile of the death assemblages found at each site was built using visual identification, a non-linear growth curve algorithm developed by Michael Etnier (2002) and ancient DNA analysis. This study uses the demographic profile to evaluate the existence of a NFS rookery within the Barkley Sound area. Ultimately the existence of a rookery depends on demonstrating the existence of four age categories: fetal/newborn, juvenile, adult and adult male. Results indicate that a rookery likely existed near DfSj-24A, but there is much less certainty for DfSi-4. Further inquiry is now possible into the economic and ecological relationships that existed between the Toquaht and the NFS within the Barkley Sound area. / February 2016

Data collected from Pribilof far seals, Callorhinus ursinus, on land (1911-89) and at sea (1958-74) are analyzed to establish biological relationships and distinguish ecological patterns that are relevant to understanding and managing northern fur seal populations. The thesis follows the development of the fur seal from conception and birth through to sexual maturity and finally to a synthesis of the earlier material in terms of population regulation, management, and reasons for the decline of the Pribilof herd. Growth curves show that male fetuses grow faster and larger than female fetuses, and that fetal size is influenced by the age, size, and reproductive history of the mother. Juvenile and adult fur seals experience pronounced seasonal increases and decreases in body length and mass. Rapid gains in mass and growth occur during a brief 1-3 month period as the population migrates through the coastal waters of northern British Columbia and Alaska on its way to the Pribilof Islands. Body mass is gradually lost during the rest of the year while fasting on land and wintering along the coasts of Washington, Oregon, and California. The timing of migration and pupping is highly synchronized from year to year and may be related to the effect of climatic conditions on pup survival during the breeding season. Predictions from a thermal budget developed for pups and the results of a seasonal decomposition of weather patterns on the Pribilof Islands show that the synchronism of births in early July corresponds to the start of three months of conditions that are optimal for growth and survival of pups. Long term fluctuations are noted in pup mass and subadult growth rates which may be related to underlying, large scale natural changes in prey abundance. Changes in the physiological condition (body growth) and vital rates (survival and reproduction) are analyzed for the period 1911-89 as the population increased and decreased. Few density dependent relationships could be demonstrated. Two hypotheses concerning the current decline of the Pribilof population are reviewed and a new, third hypothesis is proposed. The thesis also examines biases in data collection related to the effects of tagging and the handling of fur seals and outlines some directions for future research. / Science, Faculty of / Zoology, Department of / Graduate

I examined the population trends of northern fur seals (Callorhinus ursinus) using an age-specific metapopulation model that allowed migration between rookeries. Mortality and birth rates were modified to simulate future population trends. I also examined the early migratory behavior and habitat associations of pups from Bering Island (BI), Russia. I instrumented 35 pups with Mk10-AL satellite tags and stomach temperature telemeters which provided diving, foraging and location data. I hypothesized that some aspects of pup behavior from the stable BI population differed from the behavior of pups from the unstable Pribilof Islands (PI). The population model revealed that emigration did not contribute significantly to the current PI population decline. However, large source populations contributed significantly to population growth in newly colonized rookeries. A stabilization of the PI population was predicted with a 10 to 20 percent reduction in both juvenile and adult female mortality rates. The diving behavior of pups showed a general progression towards longer and deeper dives as pups aged, particularly between 1600 – 0400 (local time), that was similar to PI pup behavior. However, unlike pups from the PI, I found three main diving strategies among BI pups: 1) shallow daytime divers (mean depth = 3.56 m), 2) deep daytime divers (mean depth = 6.36 m) and 3) mixed divers (mean depth = 4.81 m). The foraging behavior of pups showed that most successful ingestion events occurred between 1600 – 0400, with successful ingestion events lasting 25.36 plus/minus 27.37 min. There was no significant difference among the three strategies in the depth of successful foraging dives. I also examined the foraging search strategies in adult females and pups. Both pups and adults conducted Levy walks, although pups foraged in smaller patches (1 km scales). Using a logistic model to determine habitat associations, I found that pup locations were positively correlated with increasing chlorophyll a concentrations, distances from shore, and sea surface temperatures, and were negatively correlated with depth. There was no significant relationship between all pup locations and the regions (peripheries or centers) or types (cyclonic or anti-cyclonic) of eddies, but ingestion event locations were related to mesoscale eddy peripheries.

This study found evidence of intermittent, multi-year residency periods in northern fur seals (Callorhinus ursinus) using stable isotope ratios in vibrissae and canine teeth. Northern fur seals migrate from the Bering Sea during summer months to lower latitudes and slightly warmer waters of the northeastern Pacific Ocean and California Current in the winter. To determine the length of time spent away from the Bering Sea, growth rate was estimated using the covarying oscillations δ13C and δ15N, estimated to be 0.09 mm/day. The δ13C and δ15N in vibrissae from 30 male fur seals showed a minimum of 13 separate periods of stable covariance covering 3.25+ cm, indicating at least 1 year in warmer, less productive waters of the northeastern Pacific Ocean. The vibrissae isotope ratios were used in conjunction with δ18O from tooth dentin growth layer groups of 20 male northern fur seals; they showed significant enrichment in δ18O in 50% of the animals at age 1-2 years, which indicates extended periods of time spent in lower latitudes in the North Pacific Ocean as δ18O is typically enriched in warmer, less productive waters. Significant changes in δ18O were found to be ~ 0.2‰ enrichment per 10º south latitude, while longitude was found to have 0.2‰ enrichment per 50˚ East longitude. These data show that latitudinal changes, those related to the southerly migration from the Bering Sea to the northeastern Pacific Ocean, are a stronger factor in the shifts in dentinal δ18O than longitudinal shifts. These intermittent periods of occupation are important when estimating population abundance of northern fur seals, especially pups and juveniles.