Browsing by Subject "whales"
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Item Open Access A Multi-Modal Approach for Investigating the Physiological Responses to Breath-Holding in Diving Mammals(2023) Blawas, Ashley MarieThe ocean environment poses several adversities to usual mammalian function. Perhaps most consequential to life is the lack of air underwater. For marine mammals, like whales and dolphins, that are required to perform breath-hold dives to forage for prey, this necessitates a unique set of adaptations to efficiently manage oxygen resources while diving. In an era of global environmental change, this hostile habitat is expected to become increasingly challenging for air-breathing mammals; warming waters will necessitate deeper foraging trips and noisier oceans may compel unplanned dives to evade perceived threats. An understanding of marine mammals’ solutions to the physiological challenges of a dually-constrained lifestyle is therefore important not only to reveal how marine mammals are built to thrive where other mammals, particularly humans, falter but also the extent to which these adaptations may scale in a changing ocean environment. In this dissertation, I explore the physiological adaptations, particularly those of the cardiovascular and respiratory systems, that this taxon has evolved to mediate the challenges associated with breath-hold diving. I take a multi-scale approach to investigating these physiological traits, exploring hypotheses at the molecular, tissue-specific, and organismal scales. Accordingly, I leverage both familiar and emerging methodologies in the field of marine mammal physiology to examine adaptations that support the extended dive capacities of whales and dolphins. Cellular and molecular responses to environmental stimuli influence tissue-specific and organismal physiological responses. Despite the inextricable link between molecular and organismal physiology, studies of the molecular adaptations of marine mammals for diving are limited, in part due to the logistical complexity of obtaining molecular samples from this difficult-to-study group. To fill this gap, my collaborators and I deployed RNA-seq and enzymatic assays to examine the molecular-level changes that occur in bottlenose dolphins (Tursiops truncatus) performing extended breath-holds (Chapter 1). We demonstrated that dolphins exhibit transcriptomic and proteomic changes that occur in a time-dependent fashion during breath-holding that could support their ability to maintain selective perfusion during diving. The upregulation of ALOX5, a gene targeted for the treatment of eosinophilic asthma in humans, and lipoxygenase suggest a mechanism by which differential gene regulation could contribute to sustained vasoconstriction during the dive response. These findings illustrate the importance of responses at the molecular level for supporting the unique physiology of marine mammals. Coordinated, tissue-specific physiological changes are central to the mammalian dive response. During dives marine mammals drastically reduce their heart rate (fH) while narrowing the blood vessels that supply their peripheral tissues, thereby slowing oxygen consumption of the heart itself as well as reducing the supply of oxygen-rich blood to non-essential tissues. The factors that modulate fH and contribute to diving bradycardia are complex, largely because they are numerous and often linked, but are crucial to understanding oxygen consumption patterns and, ultimately, whole-organism physiology and behavior. Using simultaneous electrocardiographic (ECG) recordings and respirometry, I show that whales and dolphins exhibit a strong cardiorespiratory coupling that may support the conservation of blood oxygen for hypoxia-intolerant tissues during a breath-hold. This variation in fH with breathing, or respiratory sinus arrhythmia (RSA), is modulated by breathing rate (fR) in bottlenose dolphins such that slow breathing results in larger fluctuations in fH (Chapter 2). Following a breath, fH increases rapidly to a maximum and then decreases through the end of the inter-breath interval (IBI). Notably, some of the minimum fH’s of the RSA were comparable to reported diving fH’s for this species suggesting the importance of apnea alone in modulating the fH of a diving marine mammal. I also demonstrate that this cardiorespiratory coupling scales with body size and fR across five cetacean species suggesting both physical scaling laws and dynamic physiological needs play a role in determining the magnitude of the RSA (Chapter 3). These studies highlight the complexity of tissue-specific responses and the need to contextualize physiological rates. Ultimately, it is the interactions of tissues that determine organismal physiology – the fundamental constraint on an organism’s behavior. To investigate the connection between organismal physiology and behavior, I developed a novel method for extracting fR from free-ranging whale biologging tag data (Chapter 4). I found that the high-flow rate and large tidal volume breaths of cetaceans generate movement signals which are captured by the accelerometers of biologging tags, enabling respiration event detection from historical biologging tag datasets. I applied this tool to movement data collected from short-finned pilot whales in Cape Hatteras, North Carolina using digital acoustic recording tags (DTAGs) and examined variation in respiratory patterns associated with diving (Chapter 5). I found that whales vary their pre- and post-dive surface duration and post-dive fR in proportion to the duration and activity of upcoming dives illustrating the physiological challenge of preparing for and recovering from breath-hold diving and highlighting optimization of surface behavior required to support breath-holds. Physiological responses are coordinated across multiple levels of biological organization necessitating the use of various tools and techniques to fully elucidate the adaptations that support marine mammals’ capacity to dive for minutes to hours without a breath. The findings of this dissertation underscore that the physiological function of breath-holding whales and dolphins is coordinated across scales, the physiological responses of cardiovascular and respiratory systems are linked, and sensing vital rates can provide insights into the physiological demands of a dive. Future studies should continue to focus on integrating methods across scales to better understand the physiological function of these animals and its plasticity in a changing ocean.
Item Open Access An analysis of the United States Navy's proposed undersea warfare training range(2006) Wexler, Elizabeth MIn October 2005, the United States Navy issued a Draft Environmental Impact Statement for the construction of an undersea warfare training range off the North Carolina coast. Exercises conducted in this proposed range will involve the use of mid-frequency sonar, the known cause of one mass whale stranding in the Bahamas, and the suspected cause of at least twelve other stranding events that have occurred in the past decade world-wide. In their statement, the Navy indicates the potential for limited harm to marine life. Fearing an increase in future strandings, scientists, environmentalists, and the general public have questioned the scope of the Navy’s predictions for biological damage. My review suggests that the Navy does not fully acknowledge the negative effects the training range could have, and does not appropriately use the best available scientific information. In light of this, I conclude that the Navy has not fulfilled the requirements of the National Environmental Policy Act.Item Open Access Examining the Impacts of Antarctic Tourism on Whales(2014-04-25) Fox, AllisonSince the formation of the International Association of Antarctica Tour Operators (IAATO) in 1991, the number of tourists visiting Antarctica has increased from 6,400 to over 35,000 annually. If vessel-based Antarctic tourism (known as “expedition cruising”) continues to expand, the opportunities for interactions between tourism vessels and whales will likewise increase. Potential impacts to whales from tourism range from negative impacts, such as collisions, ship noise, and behavioral modification, to positive impacts, such as tourist participation in whale research projects. My review of the available literature found that the interactions between Antarctic tourism and whales have received limited attention from the scientific community. In order to gain insight into this situation, I designed and beta-tested online surveys for Antarctic scientists, tourists, and tour operators. These surveys examine the perspectives of these groups towards the interactions between whales and Antarctic tourism. Preliminary results indicate these groups believe that Antarctic tourism currently offers more benefits to whales than risks. In the future, the distribution of similar surveys to larger groups, particularly to IAATO members and tourists on IAATO vessels, would help confirm these findings. Understanding the perceptions of each group will be useful during the development of future Antarctic guidelines and policy, and can be used to guide future Antarctic research.Item Open Access Quantifying photogrammetric accuracy for measuring humpback whales using Unmanned Aerial Systems(2017-04-27) Mason, ElizabethPhotogrammetry is the practice of obtaining accurate and valid measurements from 2D images. This practice can be useful in applications where it is dangerous or difficult to reach the target. In recent years, this practice is becoming more common in the marine science field to measure large and potentially dangerous marine mammals. Even more recently, Unmanned Aerial Systems (UAS) technology is being utilized to further minimize the dangers to humans, as well as to decrease the disturbance to animals To establish the accuracy of measurements taken from aerial imagery with UAS technology, this study calculates the distortion values from 3 different cameras, on three different UAS platforms. Lens correction values were calculated for images taken with the three cameras, a GoPro 4 Black, an Olympus E-pm2, and a Sony a5100. These lens correction values were then applied to images taken on the ground of a wooden board approximately 99.9cm long. The static ground images were taken every 10 meters up to 50 meters, to calculate the impact that distance and distortion has on the accuracy of photogrammetric measurements. Finally, each camera was attached to a different UAS platform, GoPro 4 Black with a 3D Robotics Iris+, Olympus E-pm2 with a Microcomputer HexaXL, and the Sony a5100 with a LemHex44. Images were taken at varying altitudes and were then able to be compared to the static ground images to quantify the impact that UAS has on the accuracy. The 3D Robotics Iris+ altitude measurements needed for photogrammetric calculations were derived solely from the onboard barometric sensor, while the MikroKopter and the LemHex44, altitude data were collected by an onboard barometric sensor as well as a Lightware SF11 pulse laser altimeter, thus allowing a comparison of the improved measurements obtained by using a more accurate reading of altitude. These methods were then applied to images of humpback whales (Megaptera novaeangliae) collected in the Antarctic Peninsula in January and February of 2017 with the Sony a5100. A total of 48 individuals were measured for total length, and due to the UAS testing it is known that these measurements are within 1.664 cm of the true length of the whales. Additionally, width measurements of mother calf pairs were compared allowing for an important first step in establishing important time periods of growth and size differences in genders.