This study aimed to investigate possible functions of the sounds produced by herring-eating killer whales in the Northeast Atlantic. In this study, I investigated the whistle repertoire of killer whales, which had previously only been studied in British Columbia, where it appeared to be restricted to the audible range. However, I show that high frequency whistles (> 17 kHz) were detected in Northeast Atlantic populations but not in Northeast Pacific populations. These results indicated substantial intraspecific variation in whistle production in killer whales. Little variation was observed in high frequency whistles recorded from three different sites in the Northeast Atlantic, suggesting this signal has a similar function across locations. The estimated active space of high frequency whistles and burst-pulse calls suggested that these are short-range signals used for within-group communication. Source levels of burst-pulse calls were lower than what was previously described in British Columbia, which possibly reflected the fact that these sounds do not need to propagate far because distances between group members are generally short. Calls, high frequency whistles and herding calls produced at different depths did not appear to suffer effects due to increased pressure, such as changing frequency or duration characteristics. Feeding appeared to take place below 10 m of depth, as suggested by the localisation of depth of production of feeding-related sounds. These depths were consistent with those at which tailslaps were produced in Dtags attached to individual whales. Feeding periods were characterised by deep diving, increased sound production and highly non-directional movement. These findings suggested that killer whales in a herring spawning ground use a feeding strategy different from carousel feeding used in herring overwintering grounds. These findings showed that Northeast Atlantic killer whales have a different sound repertoire to other populations, and suggested that they may employ different feeding strategies depending on prey behaviour.

For the majority of social species, group composition is dynamic, and individuals are interconnected in a heterogeneous social network. In this study I investigate the mechanisms underpinning social structure in the endangered southern resident killer whale (Orcinus Orca) population using a long term dataset, and explore the consequences of these. My results demonstrate that resource availability may be an important determinant of social network structure. A significant relationship between the connectivity of the social network and salmon abundance occurred, with a more interconnected network in years of high salmon abundance. As networks are non-random, highly connected individuals may play a key role in population processes such as information and disease transmission. While associations occurred both within and between matrilines, females had a significantly higher number of associates than males, as did older individuals of both sexes. Older males played a more important role in interconnecting the network. The attributes of group leadership were then investigated in matrilines and in individuals. Leadership was not a factor of size or mean age of matriline. However, there was a significant relationship between leadership score and the matriline sex ratio. Individually, females had higher leadership scores than males, and there was a positive correlation between leadership score and age in both sexes. I suggest that the oldest females have the highest 4 leadership scores due to increased ecological knowledge that comes with a prolonged lifespan. Using multi-generational records for two populations of killer whales, I show that both reproductive and post-reproductive mothers increase the survival of offspring, particularly in older male offspring. This is consistent with theoretical predictions, and may explain why female killer-whales have evolved the longest post-reproductive lifespan of all non-human animals. Given the role that individuals of high network centrality can play in population processes, understanding the driving forces behind social network structure is vital when designing effective conservation and management plans.

Although Icelandic and Norwegian killer whales are thought to have been in contact prior to the collapse of the herring stock in the 1960s, the Northeast Atlantic killer whales currently seem to show high site fidelity. So far, photoidentification data have suggested movement of a few individuals between East Iceland and North Scotland, and two calls have been shown to be shared by the Icelandic and Norwegian populations. Based on previous and newly analysed call samples, the aim of this study was to describe the geographic variation in the vocal repertoire of the Northeast Atlantic killer whales. Recordings have been conducted off Southwest Iceland in the summers 2004, 2008 and 2009 using sound recording tags attached using suction cups (Dtags), a 4-element vertical hydrophone array and a 2-element towed hydrophone array. From the 57 hours of recording analysed, 1742 calls were classified. In total, 56 distinct call categories composed of 35 call types and 31 subtypes were identified. This discrete call repertoire contained less biphonic calls but more calls composed of buzzes and/or clicks than the Norwegian repertoire. The reasons for these differences remain unknown. One Icelandic call subtype was defined as a compound call, a type of call that is common in the Norwegian population. The comparison of the different vocal repertoires of Northeast Atlantic showed four good or likely call matches in herring-eating killer whales (one between Southwest Iceland and Shetland, one between East Iceland and Norway, and two between Shetland and Norway). No matches were found between Southwest Iceland and East Iceland. I suggest that the four shared calls are most likely to have come from a common ancestral pod and have been transmitted through vocal learning. Over time, geographic isolation of the groups induced by changes in the migratory patterns of the herring might have been accompanied by divergence in their call repertoires.

A study was conducted using data compiled from two sources to test the hypothesis that killer whales display seasonal variability in their occurrence in the Galapagos Marine Reserve (GMR), Ecuador. Three questions arise from this hypothesis: 1) do killer whale sightings display temporal variability; 2) are sightings spatially associated with resources; and 3) if sightings are spatially associated with resources, does the spatial association change temporally? I combined and evaluated two sets of GMR killer whale sighting data (n=154) spanning a twenty-year time frame collected via opportunistic sightings by an observer network and shipboard line-transect surveys. I tested for a (a) correlation between the total annual sightings and bi-annual seasonality (upwelling versus non-upwelling); (b) correlation between the total annual sightings and the Multivariate El Nino Southern Oscillation Index (MEI); (c) correlation between sightings, the MEI, and seasonality; (d) spatial association between sightings and resources; and (e) spatial change in sightings with seasonality. Sightings were roughly equally distributed between non-upwelling (56%) and upwelling seasons (July-December). No direct correlation was found between sightings and the MEI. Sightings occurred more often than expected by chance during the peak upwelling months of August-November when the MEI was within one standard deviation of the average (binomial z=2.91, p<0.05). Sightings were spatially associated with areas of high chlorophyll a values (binomial z=4.46, p&lt;0.05), pinniped rookeries (binomial z=6.03, p&lt;0.05), and areas with high combined resource value (binomial z=5.36, p&lt;0.05). The spatial distribution of sightings did not shift with seasonality, with the exception that sightings occurred less often than expected in areas of low combined resource value during the upwelling period (binomial z=-3.17, p&lt;0.05). Though variability in observer effort should be considered when evaluating these data, these results do not suggest a strong pattern of seasonal occupancy or that killer whales are responsive to El Nino Southern Oscillation events. Further research is needed to determine if killer whales in the GMR comprise a single resident population, multiple resident and transient populations, or if killer whales observed in the GMR are part of a population inhabiting the eastern tropical Pacific region, which visit the area at various times.

Thesis (Ph. D.)--Joint Program in Biological Oceanography (Massachusetts Institute of Technology, Dept. of Biology, and the Woods Hole Oceanographic Institution), 2000. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution Joint Program in Oceanography/Applied Ocean Science and Engineering, 2000. / "Funding was provided by grants from WHOI's Rinehart Coastal Research Center and Ocean Ventures Fund, a National Science Foundation graduate fellowship, grant CC-S-611002-001-C from the Office of Naval Research, and broad financial support from WHOI's Education Department. Includes bibliographical references.

The purpose of this study is to explore the implications of the historical perspective when it is linked to the ecological concept of adaptive management. The vehicle for this exploration is a genetically distinct population of killer whales (Orcinus orca), whose core coastal habitat includes the inland waters of Georgia Strait, Juan de Fuca Strait and Puget Sound; a geographic region referred to as the “Salish Sea.” This stock of killer whales, known as the Southern Resident Community, is unique in having a detailed scientific record that spans over two decades and recently this population was listed as “threatened” by the Committee on the Status of Endangered Wildlife in Canada (April 1999). The goal of this study is to take account of the specific ecological history of this killer whale population, and provide an assessment of the resiliency of this stock to withstand present levels of human impacts. In Chapter 1 the academic concepts of historical ecology and adaptive management are reviewed in preparation for their application as theory. Chapter 2 is an inventory of the ecological domain, in which the focal population is assessed by temporally measurable indicators o f its ecological status: population dynamics, feeding ecology, and habitat use. In Chapter 3 temporally measurable indicators of stress such as predation, disease, food resource depletion, toxic exposure, surface disturbance, and underwater noise are examined for their impact upon the carrying capacity of the environment of the whales. Chapter 4 plots both sets of indicators historically as trends in variation from the Sample Mean at different time scales (months, years, decades, centuries), and indexes them in terms of perturbations from the historical norm. In Chapter 5 four basic types of historical trends in environmental impacts are identified that are directly relevant to evaluating the resilience of the management unit. These are: (1) Relic impacts - potential impacts that are no longer present, but may account for present conditions. (2) Adapted impacts - potential impacts that have been around long enough for the management unit to have adapted to them. (3) Cumulative impacts- potential impacts that accumulate slowly in the environment or life history of the management unit before exerting environmental resistance. (4) New impacts - potential impacts with which the management unit has not had previous experience. These four historical criteria allow the manager to identify the most sensitive impacts for present conditions, and identify scales of management for restorative intervention. This resiliency index should have application for most types of ecological systems, or management units, because it describes very generalized types of temporal outcomes, independent of scale and life history pattern of the management unit. In terms of the focal population of killer whales in this study, the historical assessment suggests that: 1) these whales are presently a remnant population due to killing and capture by European settlers from the turn of the century to the 1970s; 2) they have bio-accumulated toxins during the highest historical periods of environmental pollution in the Salish Sea, and this toxic exposure will continue to increase for the whales over the next few decades; 3) this killer whale population has never previously experienced a lack of salmon, so diminishing salmon stocks are potentially a new stress on them; and 4) these killer whales have adapted to vessel traffic and noise for several decades in relation to vessel-based salmon fishing operations, and that this influence has recently been replaced by record levels of whale watching traffic, which potentially poses more severe impacts than fishing vessels because the boats follow the whales, rather than their prey. This historical assessment facilitates the application of “adaptive management” strategies for these whales by providing the basis for predicting the current “resiliency” of this population to adapt to environmental conditions. / Graduate

Marine mammals are in a precarious conservation position because of anthropogenic impacts and historic perceptions that they are a consumable commodity. In light of changing abiotic conditions, further evaluation is needed on the habitat use, behavior, and interactions among marine mammals. Conservation legislation has helped protect species, but the greatest ground swelling may be the advent of the commercial whale watching industry. The feeding grounds in Alaskan waters have made this area a prime tourism location, and these nutrient-rich waters have resulted in a confluence of marine mammal species, including the appealing and abundant humpback whale (Megaptera novaeangliae) that may associate with three ecotypes of killer whales (Orcinus orca). These species are interesting because they may travel together to feed on prey or be adversaries in a predator-prey relationship. Using whale watching as a platform, this study evaluated the effects of the presence of these two species separately and together, and of the type of interaction between them, on human perception. Data were collected via opportunistic observations and a retrospective pre- and post-survey instrument. Differences in humpback whale distribution and group size patterns were found relative to killer whale occurrence, although humpback whale behavioral states were unchanged. Changes in passenger conservation attitudes could not be attributed to species and behaviors but they were important determinates to whale watching satisfaction. Overall, more positive conservation attitudes and an increase in knowledge about marine mammals were reported after whale watching. These tours provide an opportunity for collecting meaningful scientific data and providing more in-depth education such as enhancing the appreciation for ecosystem services provided by marine mammals.

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

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 331-339).