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This thesis examines sound production of eastern gray whales (Eschrichtius robustus) in the wintering lagoons to determine whether sound use is a function of social context. Proportions of sounds used, parameters of each sound class, and rates of sounds were compared among social contexts. Data revealed the strong possibility of context-specific use for particular sound classes. Additionally, sound parameters and rates of production varied by social context. These results reflect similar variations in gray whale repertoire throughout their range that may be due to changes in social and behavioral contexts. Gray whale sounds are classified into several classes based on aural and visual characteristics. This study verifies the classification system determined in previous studies, with the exception of class 8, and supports the division of class 1 into subclasses 1a and 1b. Class 1 appeared to be critical during sexual contexts and all highly social contexts, regardless of age and sex class. Although highly recognizable, its parameters exhibited much variation among social contexts; therefore class 1 may communicate graded emotional states in short-range interactions. Other classes of sounds may be utilized for long-distance communication, as startle responses, or "precursors" to the adult repertoire. Frequency-related parameters of all sound classes showed variation among social contexts, but duration demonstrated very little variation. Calf-containing contexts exhibited greatest and most varied frequencies; this is to be expected if gray whale's sound mechanism is related to body and tracheal length. Variation also may indicate that physical maturity or learning play a role in the repertoire development. The lowest and least varied frequencies were observed in adult contexts. Sound production rates also varied by social context. Active adults produced sounds at high rates during short intervals; mixed/unknown contexts were often silent. Calf-containing contexts produced sounds at intermediate rates and were never silent. The correlations demonstrated here between social context and use of sounds will allow for acoustics to be an indicator of group composition, seasonal movements, and social patterns, thus relieving dependency on difficult visual observation. Additionally, such correlations provide preliminary information for determining sound functions.

A small number of eastern north Pacific gray whales (Eschrichtius robustus), known as the Pacific Coastal Feeding Group (PCFG) forage during the summer months in the coastal waters between California and Alaska. Although several studies have analyzed the population structure of the PCFG, maternal learning and predator/prey dynamics have not been studied in detail. In this study I characterize fine scale habitat use and site fidelity of eastern north Pacific gray whales in one foraging site within the PCFG’s foraging range. I approach this study by examining site fidelity to Clayoquot Sound in increasing detail at different time scales. Using the variability recorded in 17 field seasons of whale census surveys (1997-2013) as a proxy for fluctuations in prey, I suggest that the combination of physical properties of the study area and the life history characteristics of the primary prey species type enable Clayoquot Sound to persist as a foraging site through time. The analysis of photographic identification data collected between 1998-2013 indicates that Clayoquot Sound is one site within a larger foraging range, and that annual fluctuations in prey density are related to site fidelity and residency time. By identifying cow/calf pairs using photographic identification data collected between 1998-2013 I characterize internal recruitment via maternal learning within Clayoquot Sound. A calf’s site fidelity is related to its mother’s site fidelity, but its residency time is related to annual fluctuations in prey density. In contrast, a cow’s residency time is not related to changes in prey, but increases in duration when accompanied by a calf. The interplay between fluctuations in prey productivity, and the age and gender of individuals, are the variables that most likely influence the distribution of PCFG whales intra- and inter-annually. / Graduate / 0306

In this study, I present a new approach to prey quantification in the context of the predator-prey relationship between an apex marine predator, the gray whale, (Eschrichtius robustus) and one of its primary prey, mysids (Family Mysidae) in a tertiary foraging area, in Clayoquot Sound, on the west coast of Vancouver, Island, British Columbia. With the use of a remote acoustical sounder, I first quantify mysid patches in the presence of foraging gray whales. Second, I address the biomass in those patches using a new approach to quantification. By creating an estimate of total biomass of mysids in the study area concurrently with the presence of gray whales, I demonstrate the effect that the foraging whales have on their prey. Tracking the changes of the number of whales and the number of patches, including the overall biomass of the patches provides evidence for this relationship. As the number of gray whales in the study area increases steadily from May to July, 2004, the number of mysid patches and biomass decrease during the same period. The number of foraging whales located in the study area ranged from only five in May to thirty-one on July 18th, in a region covering only 25 km of the southwest coast of Flores Island. After this period of foraging, the whales deserted the study area completely, and only one whale was seen during the month of August. The mysid population regroups slightly after the pressure of foraging whales is released, the number of patches and biomass increase a small amount, exhibiting the expected behavioral response of the prey to re-aggregate into tight swarms. The acoustic method for prey quantification is described in detail as this is a first application of this technology to the mysid-gray whale relationship. In this approach, l demonstrate that the Distorted Wave Borne Approximation model (DWBA) is useful to estimate mysid populations. This study provides a key piece in the progression of eight years of ongoing research on the foraging ecology of gray whales in Clayoquot Sound, British Columbia.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

The abundance of gray whales along the coast of Flores Island, BC, varies on an annual basis. This thesis searches for a relationship between gray whale abundance in this area and environmental forcing factors. Regression analysis was used to search for relationships, using gray whale abundance as the dependent variable and sea-surface temperature, salinity, wind speed, upwelling indices and hours of bright sunlight. Independent variables were also lagged against gray whale abundance to search for time lags between variables. When combine in a multiple regression model, wind speed and upwelling lagged two years explained 89.6% (p = 0.004) of the variance in gray whale abundance. A possible pathway for this relationship may exist through local kelp populations, which have the ability to affect gray whale prey abundance.

Understanding the ecology of an organism is fundamental for defining conservation and management priorities for wildlife and natural ecosystems. The most basic ecological framework identifies the key components of an organism's habitat, and the scale for measuring the quality of those features. How these core needs are expressed and vary in the surrounding ecosystem changes over time and space. In marine systems, the physical environment has few strict boundaries, and variations regularly occur on a scale from days to decades. The dynamic and patchy nature of marine habitat makes defining the ecological roles of an animal difficult, even where baseline data exists. In this study I analyze long term field records on the ecological interactions between foraging gray whales (Eschrichtius robustus), and their mysid prey (Family mysidae) in Clayoquot Sound, B.C. By looking at spatial and temporal shifts at both trophic levels, I measure foraging responses and requirements, and assess prey resource availability and resiliency in the marine environment at a series of scales. Appreciation for bottom-up and topdown trophic interactions provides the foundation for identifying natural variability in marine habitat, and a baseline for conservation measures that seek to use marine predators as a barometer of broader ecosystem health.