Thesis (Ph.D.) in Biological Sciences--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaves 136-165).

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Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 71-77).

vii, 55 leaves : ill. ; 28 cm Typescript. (Another copy on microfilm is located in Archives) Thesis (M.S.)--University of Oregon Includes vita and abstract Bibliography: leaves 52-56 University of Oregon theses, Dept. of Biology, M.S., 1981

Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 84-90). Description: xiv, 90 leaves : ill. ; 29 cm.

Harbour seals throughout their range are known to "haul out" onto land according to a daily cycle, which has never been fully investigated. This cycle may represent a tradeoff between the need to forage and the need to avoid aquatic predators; if so, seals should forage when prey availability is greatest and remain hauled at other times. A model based upon these premises accounted for approximately two thirds of the variation in observed hauling behaviour at a harbour seal colony in the Strait of Georgia, once other environmental effects had been filtered from the data. Some such effects could not be corrected for; since air temperature and solar radiation follow the same general pattern as that predicted by the hauling model, the possibility that hauling occurs in response to thermal conditions could not be excluded. This issue was addressed by correlating hauling activity at three seal colonies with "flux" Fs, an index of heat exchange between a seal and its environment. Once time of day and tidal effects were accounted for, there was no evidence of a positive correlation between hauling and Fs. However, under warm summer conditions there was a steep negative relationship. This is consistent with the possibility that hauled harbour seals are vulnerable to hyperthermia due to their adaptation to an aquatic lifestyle; the same blubber layer which keeps them warm when immersed may make it difficult for them to lose excess heat when on land. This was confirmed by a series of controlled experiments. Captive seals overheated when exposed to a radiant thermal environment similar to that in which wild animals stopped hauling. These data allowed me to derive an equation which described the rate of change in a seal's core temperature as a function of both present core temperature and Fs. I incorporated this function into a simulation model which described hauling behaviour in terms of a foraging/predator-avoidance tradeoff. The model performed well when used to predict the haul out durations of a sample of wild radio-tagged harbour seals in a known thermal environment. However, it is apparent that the processes which constrain hauling in this species are somewhat better understood than those which presumably cause it. An understanding of the foraging efficiency of harbour seals throughout the day, and of the predation risks they face, is probably fundamental to an understanding of hauling; yet these issues remain virtually unexplored. / Science, Faculty of / Zoology, Department of / Graduate

Worldwide harbour seal populations are showing differing and fluctuating trends in abundance, but the drivers of change remain uncertain. Within the Moray Firth, NE Scotland, count surveys carried out over the last 20 years highlighted the development of a new breeding site, providing a unique opportunity to carry out an individual-based study of harbour seal demography and pupping phenology using photo-identification techniques within a mark-recapture framework. Sightings of individual seals suggested that a large proportion of harbour seals are year-round residents at haul-out sites. Both sexes displayed high levels of between-year breeding site fidelity as well as seasonal variation in their haul-out behaviour. Apparent sex-specific survival rates (0.89♂, 0.97♀) and birth rates (0.88) were high. There was a strong correlation between lactation durations and the timing of pupping, suggesting that shifts in pupping phenology are a result of energetic constraints. This highlights the potential for using the timing of pupping as an indicator of ecosystem conditions. This study provided the first concurrent real-time estimates of survival and fecundity in a naturally regulated population of harbour seals. Demographic parameters and physiological responses indicate that prevailing conditions within the Moray Firth are favourable, and that this population should be recovering. However, observed patterns may also be an artefact of the long-term decline having caused an increase in per capita food availability through the reduction in intra-specific competition. This study highlights the current and long-term importance of individual-based data in understanding population dynamics. Through the identification of sentinel sites around the world, harbour seals could provide a single-species indicator of coastal ecosystem conditions in the Northern Hemisphere.

Thesis (Ph. D.)--Oregon State University, 1987. / Bibliography: leaves 153-177. Also available on the World Wide Web.

Thesis (M.Sc.) -- Memorial University of Newfoundland, 1984. / Bibliography : leaves 86-90. Also available online.

Thesis (M.S.) in Wildlife Ecology--University of Maine, 2005. / Includes vita. Includes bibliographical references (leaves 60-64).