Lack of knowledge regarding beaked whale biology restricts our ability to evaluate their vulnerability to anthropogenic threats. This work addresses critical data gaps in Blainville's beaked whale social structure and communication systems. Social analysis shows that Blainville's beaked whales in the Bahamas exhibit group living through a harem structure characterised by a single male accompanying a group of females for up to a year. This study also reveals that females preferentially associate with conspecifics in the same reproductive state, remaining together for up to three years. I show what may be the first example of social philopatry in beaked whales, with adult males possibly providing protection for kin. Analysis of data from acoustic tags reveals previously undescribed sexually distinctive vocalisations. These sounds might serve a communicative function helping to form and maintain groups. Acoustic data also reveals a distinctive double click pattern in Blainville's beaked whales that is likely physiological in nature. The same pattern is also shown in two other deep diving species, Cuvier's beaked whales and sperm whales. Species differences in the frequency of production of these double clicks may be providing a window into the evolution of odontocete echolocation. Data from a bottom-mounted hydrophone array reveals a lack of sex and / or age specific information in this species' echolocation clicks. Analysis of mother-calf pairs indicate calves from at least three months of age echolocate using clicks similar to those of adults. This work provides the first comprehensive study of possible communicative sounds in an elusive deep-diving cetacean species exhibiting a complex social structure that lies somewhere between stable groups and fission-fusion societies. Understanding the interaction between communication and social organisation enhances our ability to predict the effects of anthropogenic disturbance on this species.

I examined the dynamics of an endangered population of northern bottlenose whales over a 23-year period during which its prime habitat, the Gully canyon, was made a Marine Protected Area (MPA). Using mark-recapture techniques on photo-identifications I estimate a current population of 116 animals (95% CI=101-130). The population size and sex-ratio have remained stable since before the MPA designation suggesting this population is persisting. I used photo-identifications and high definition videography to examine the social organization of northern bottlenose whales, including behavioural synchrony. Relationships are highly variable; most associations are short-lived, but there are also long-term preferred associations lasting from several years (female/immature dyads) to over a decade (mature male dyads). I found little, if any, division of the social community. Synchronized breathing is common, precise, and appears to vary with behaivoural context. Although speculative, synchronized breathing might play a role the maintenance of general social relationships within this population.

An important step for protecting Endangered species is the identification of critical habitat. This can be especially challenging for deep ocean species. Northern bottlenose whales (Hyperoodon ampullatus) are deep-diving beaked whales of the North Atlantic. A population of this species occurs along the edge of the Scotian Shelf primarily in three submarine canyons that have been identified as critical habitat for the population: the Gully (the largest submarine canyon off eastern North America), Shortland Canyon and Haldimand Canyon. The Scotian Shelf population is considered Endangered mainly due to its small numbers and the anthropogenic threats it faces. The primary objective of my research was to further identify critical habitat of the population using passive acoustic monitoring, increasing knowledge of how the whales use the canyons and adjacent areas throughout the year. A review of the literature on cetacean associations with submarine canyons indicates that various mechanisms may act to attract cetaceans to these features. While many different species occur in canyons globally, they appear to be particularly important habitat for beaked whales. I developed an automated click detection algorithm customized for detecting northern bottlenose whale echolocation clicks, and long-term acoustic recordings were analyzed to examine the presence and relative abundance of northern bottlenose whales on the Scotian Slope over various spatial and temporal scales. The whales occurred in the area consistently throughout the year and all three canyons, as well as the area between canyons, appeared to be important foraging grounds for the population. The whales displayed diurnal foraging patterns. I also investigated niche separation between northern bottlenose whales and sperm whales (Physeter macrocephalus), another deep diving species. The presence of the two species was positively correlated over all spatial and temporal scales examined. These results indicate that areas within and adjacent to the Gully are important foraging grounds for northern bottlenose whales throughout the year. Furthermore, in addition to the canyons themselves, the shelf-edge areas between the Gully, Shortland and Haldimand canyons may constitute critical habitat for the whales. This research will be used to inform management measures relevant to the protection and recovery of this Endangered population.

The Littoral Acoustic Demonstration Center has collected passive acoustic monitoring data in the northern Gulf of Mexico since 2001. Recordings were made in 2007 near the Deepwater Horizon oil spill that provide a baseline for an extensive study of regional marine mammal populations in response to the disaster. Animal density estimates can be derived from detections of echolocation signals in the acoustic data. Beaked whales are of particular interest as they remain one of the least understood groups of marine mammals, and relatively few abundance estimates exist. Efficient methods for classifying detected echolocation transients are essential for mining long-term passive acoustic data. In this study, three data clustering routines using k-means, self-organizing maps, and spectral clustering were tested with various features of detected echolocation transients. Several methods effectively isolated the echolocation signals of regional beaked whales at the species level. Feedforward neural network classifiers were also evaluated, and performed with high accuracy under various noise conditions. The waveform fractal dimension was tested as a feature for marine biosonar classification and improved the accuracy of the classifiers. [This research was made possible by a grant from The Gulf of Mexico Research Initiative. Data are publicly available through the Gulf of Mexico Research Initiative Information & Data Cooperative (GRIIDC) at https://data.gulfresearchinitiative.org.] [DOIs: 10.7266/N7W094CG, 10.7266/N7QF8R9K]

Bottlenose dolphins (Tursiops truncatus) and other odontocete cetaceans rely on sound for communication, navigation, and foraging. Therefore, hearing is one of their primary sensory modalities. Both natural and anthropogenic noise in the marine environment could mask the ability of free-ranging dolphins to detect sounds, and chronic noise exposure could cause permanent hearing losses. In addition, several mass strandings of odontocete cetaceans, especially beaked whales, have been correlated with military exercises involving mid-frequency sonar, highlighting unknowns regarding hearing sensitivity in these animals.Auditory evoked potential (AEP) methods are attractive over traditional behavioral methods for measuring the hearing of marine mammals because they allow rapid assessments of hearing sensitivity and can be used on untrained animals. The goals of this study were to 1.) investigate the differences among underwater AEP, in-air AEP, and underwater behavioral heari ng measurements using two captive bottlenose dolphins, 2.) investigate the hearing abilities of a population of free-ranging bottlenose dolphins in Sarasota Bay, Florida, using AEP techniques, and 3.) report the hearing abilities of a stranded juvenile beaked whale (Mesoplodon europaeus) measured using AEP techniques.For the two captive dolphins, there was generally good agreement among the hearing thresholds determined by the three test methods at frequencies above 20 kHz. At 10 and 20 kHz, in-air AEP audiograms were substantially higher (about 15 dB) than underwater behavioral and underwater AEP audiograms.For the free-ranging dolphins of Sarasota Bay, Florida, there was considerable individual variation, up to 80 dB between individuals, in hearing abilities. There was no relationship between age, gender, or PCB load and hearing sensitivities. Hearing measured in a 52-year-old captive-born bottlenose dolphin showed similar hearing thresholds to the Sarasota dolphins up to 80 kHz, but exhibited a 50 dB drop in sensitivity at 120 kHz.Finally, the beaked whale was most sensitive to high frequency signals between 40 and 80 kHz, but produced smaller evoked potentials to 5 kHz, the lowest frequency tested. The beaked whale hearing range and sensitivity were similar to other odontocetes that have been measured.