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Aptos, CA, United States

Goldbogen J.A.,Stanford University | Hazen E.L.,National Oceanic and Atmospheric Administration | Friedlaender A.S.,Oregon State University | Calambokidis J.,Cascadia Research Collective | And 4 more authors.
Functional Ecology

Despite their importance in determining the rate of both energy gain and expenditure, how the fine-scale kinematics of foraging are modified in response to changes in prey abundance and distribution remain poorly understood in many animal ecosystems. In the marine environment, bulk-filter feeders rely on dense aggregations of prey for energetically efficient foraging. Rorqual whales (Balaenopteridae) exhibit a unique form of filter feeding called lunge feeding, a process whereby discrete volumes of prey-laden water are intermittently engulfed and filtered. In many large rorqual species the size of engulfed water mass is commensurate with the whale's body size, yet is engulfed in just a few seconds. This filter-feeding mode thus requires precise coordination of the body and enlarged engulfment apparatus to maximize capture efficiency. Previous studies from whale-borne tags revealed that many rorqual species perform rolling behaviours when foraging. It has been hypothesized that such acrobatic manoeuvres may be required for efficient prey capture when prey manifest in small discrete patches, but to date there has been no comprehensive analysis of prey patch characteristics during lunge feeding events. We developed a null hypothesis that blue whale kinematics are independent of prey patch characteristics. To test this hypothesis, we investigated the foraging performance of blue whales, the largest filter-feeding predator and their functional response to variability in their sole prey source, krill using a generalized additive mixed model framework. We used a combination of animal-borne movement sensors and hydroacoustic prey mapping to simultaneously quantify the three-dimensional foraging kinematics of blue whales (Balaenoptera musculus) and the characteristics of targeted krill patches. Our analyses rejected our null hypothesis, showing that blue whales performed more acrobatic manoeuvres, including 180° and 360° rolling lunges, when foraging on low-density krill patches. In contrast, whales targeting high-density krill patches involved less manoeuvring during lunges and higher lunge feeding rates. These data demonstrate that blue whales exhibit a range of adaptive foraging strategies that maximize prey capture in different ecological contexts. Because first principles indicate that manoeuvres require more energy compared with straight trajectories, our data reveal a previously unrecognized level of complexity in predator-prey interactions that are not accounted for in optimal foraging and energetic efficiency models. © 2014 British Ecological Society. Source

Southall B.L.,Southall Environmental Associates Inc. | Southall B.L.,University of California at Santa Cruz | Southall B.L.,Duke University | Moretti D.,Naval Undersea Warfare Center | And 4 more authors.
Marine Technology Society Journal

Behavioral response studies (BRS) are increasingly being conducted to better understand basic behavioral patterns in marine animals and how underwater sounds, including from human sources, can affect them. These studies are being enabled and enhanced by advances in both acoustic sensing and transmission technologies. In the design of a 5-year project in southern California ("SOCAL-BRS"), the development of a compact, hand-deployable, ship-powered, 15-element vertical line array sound source enabled a fundamental change in overall project configuration from earlier efforts. The reduced size and power requirements of the sound source, which achieved relatively high output levels and directivity characteristics specified in the experimental design, enabled the use of substantially smaller research vessels. This size reduction favored a decentralization of field effort, with greater emphasis on mobile small boat operations capable of covering large areas to locate and tag marine mammals. These changes in configuration directly contributed to significant increases in tagging focal animals and conducting sound exposure experiments. During field experiments, received sound levels on tagged animals of several different species were within specified target ranges, demonstrating the efficacy of these new solutions to challenging field research problems. Source

Stimpert A.K.,Naval Postgraduate School, Monterey | Stimpert A.K.,Moss Landing Marine Laboratories | Deruiter S.L.,University of St. Andrews | Southall B.L.,Southall Environmental Associates Inc. | And 6 more authors.
Scientific Reports

Beaked whales are hypothesized to be particularly sensitive to anthropogenic noise, based on previous strandings and limited experimental and observational data. However, few species have been studied in detail. We describe the underwater behavior of a Baird's beaked whale (Berardius bairdii) from the first deployment of a multi-sensor acoustic tag on this species. The animal exhibited shallow (23 ± 15 m max depth), intermediate (324 ± 49 m), and deep (1138 ± 243 m) dives. Echolocation clicks were produced with a mean inter-click interval of approximately 300 ms and peak frequency of 25 kHz. Two deep dives included presumed foraging behavior, with echolocation pulsed sounds (presumed prey capture attempts) associated with increased maneuvering, and sustained inverted swimming during the bottom phase of the dive. A controlled exposure to simulated mid-frequency active sonar (3.5-4 kHz) was conducted 4 hours after tag deployment, and within 3 minutes of exposure onset, the tagged whale increased swim speed and body movement, and continued to show unusual dive behavior for each of its next three dives, one of each type. These are the first data on the acoustic foraging behavior in this largest beaked whale species, and the first experimental demonstration of a response to simulated sonar. Source

Benoit-Bird K.J.,Oregon State University | Southall B.L.,Southall Environmental Associates Inc. | Moline M.A.,University of Delaware
Proceedings of the Royal Society B: Biological Sciences

We targeted a habitat used differentially by deep-diving, air-breathing predators to empirically sample their prey’s distributions off southern California. Fine-scale measurements of the spatial variability of potential prey animals from the surface to 1 200 m were obtained using conventional fisheries echosounders aboard a surface ship and uniquely integrated into a deep-diving autonomous vehicle. Significant spatial variability in the size, composition, total biomass, and spatial organization of biota was evident over all spatial scales examined and was consistent with the general distribution patterns of foraging Cuvier’s beaked whales (Ziphius cavirostris) observed in separate studies. Striking differences found in prey characteristics between regions at depth, however, did not reflect differences observed in surface layers. These differences in deep pelagic structure horizontally and relative to surface structure, absent clear physical differences, change our long-held views of this habitat as uniform. The revelation that animals deep in the water column are so spatially heterogeneous at scales from 10 m to 50 km critically affects our understanding of the processes driving predator–prey interactions, energy transfer, biogeochemical cycling, and other ecological processes in the deep sea, and the connections between the productive surface mixed layer and the deep-water column. © 2016 The Author(s) Published by the Royal Society. All rights reserved. Source

Ellison W.T.,Marine Acoustics Inc. | Southall B.L.,Southall Environmental Associates Inc. | Southall B.L.,University of California at Santa Cruz | Clark C.W.,Cornell University | Frankel A.S.,Marine Acoustics Inc.
Conservation Biology

Acute effects of anthropogenic sounds on marine mammals, such as from military sonars, energy development, and offshore construction, have received considerable international attention from scientists, regulators, and industry. Moreover, there has been increasing recognition and concern about the potential chronic effects of human activities (e.g., shipping). It has been demonstrated that increases in human activity and background noise can alter habitats of marine animals and potentially mask communications for species that rely on sound to mate, feed, avoid predators, and navigate. Without exception, regulatory agencies required to assess and manage the effects of noise on marine mammals have addressed only the acute effects of noise on hearing and behavior. Furthermore, they have relied on a single exposure metric to assess acute effects: the absolute sound level received by the animal. There is compelling evidence that factors other than received sound level, including the activity state of animals exposed to different sounds, the nature and novelty of a sound, and spatial relations between sound source and receiving animals (i.e., the exposure context) strongly affect the probability of a behavioral response. A more comprehensive assessment method is needed that accounts for the fact that multiple contextual factors can affect how animals respond to both acute and chronic noise. We propose a three-part approach. The first includes measurement and evaluation of context-based behavioral responses of marine mammals exposed to various sounds. The second includes new assessment metrics that emphasize relative sound levels (i.e., ratio of signal to background noise and level above hearing threshold). The third considers the effects of chronic and acute noise exposure. All three aspects of sound exposure (context, relative sound level, and chronic noise) mediate behavioral response, and we suggest they be integrated into ecosystem-level management and the spatial planning of human offshore activities. © 2011 Society for Conservation Biology. Source

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