This dissertation uses videocameras, tags and acoustic recorders to investigate the diving and acoustic behavior of sperm whales in the Gulf of Alaska during natural and depredation foraging conditions. First, underwater videocamera footage of a sperm whale attacking a fisherman's longline at 100 m depth was used to examine its acoustic behavior at close range and to estimate its size both acoustically and visually. Second, bioacoustic tagging data demonstrated that the same individuals displayed different acoustic behaviors during natural and depredation foraging states. Two broad categories of depredation, "shallow" and "deep," were also identified. These results suggest that passive acoustic monitoring at close ranges may yield useful metrics for quantifying depredation activity. Third, the behavioral reactions of depredating sperm whales to a variety of acoustic play¬backs generated at relatively low source levels were investigated using bioacoustic tags. Finally, bioacoustic and satellite tag data were used to develop passive acoustic techniques for tracking sperm whales with a short -aperture two-element vertical array. When numeric sound propagation models were exploited, localization ranges up to 35 km were obtained. The tracking methods were also used to estimate the source levels of sperm whale "clicks" and "creaks", predict the maximum detection range of the signals as a function of sea state, and measure the drift of several whales away from a visual decoy

The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from 89 different studies. Hundreds of reports of unusual species observations from around the world suggest that animals quickly responded to the reductions in human presence. However, negative effects of lockdown on conservation also emerged, as confinement resulted in some park officials being unable to perform conservation, restoration and enforcement tasks, resulting in local increases in illegal activities such as hunting. Overall, there is a complex mixture of positive and negative effects of the pandemic lockdown on nature, all of which have the potential to lead to cascading responses which in turn impact wildlife and nature conservation. While the net effect of the lockdown will need to be assessed over years as data becomes available and persistent effects emerge, immediate responses were detected across the world. Thus, initial qualitative and quantitative data arising from this serendipitous global quasi-experimental perturbation highlights the dual role that humans play in threatening and protecting species and ecosystems. Pathways to favorably tilt this delicate balance include reducing impacts and increasing conservation effectiveness.